What are the main components of the endocrine system. How does the endocrine system interact with other organ systems. Why is the pituitary gland considered the master gland. What role does the hypothalamus play in endocrine function. How do hormones travel throughout the body. What are some examples of endocrine system responses to stimuli.

The Major Endocrine Glands and Their Functions

The endocrine system is a complex network of glands that produce and secrete hormones directly into the bloodstream. These hormones act as chemical messengers, regulating various bodily functions and maintaining homeostasis. Let’s explore the key endocrine glands and their roles:

Pituitary Gland: The Master Regulator

The pituitary gland, often referred to as the “master gland,” is a pea-sized structure located at the base of the brain. It produces and releases several important hormones that control other endocrine glands and regulate various bodily functions. Some key hormones produced by the pituitary gland include:

• Growth hormone (GH): Stimulates growth and cell reproduction
• Adrenocorticotropic hormone (ACTH): Stimulates the adrenal glands to produce cortisol
• Thyroid-stimulating hormone (TSH): Regulates the thyroid gland’s function
• Follicle-stimulating hormone (FSH) and Luteinizing hormone (LH): Control reproductive functions

Thyroid Gland: Metabolism Regulator

The thyroid gland, located in the neck, produces thyroid hormones that play a crucial role in regulating metabolism, body temperature, and energy production. The main hormones secreted by the thyroid gland are:

• Thyroxine (T4)
• Triiodothyronine (T3)

Parathyroid Glands: Calcium Balance Maintainers

The parathyroid glands, four small glands located behind the thyroid, produce parathyroid hormone (PTH). This hormone is essential for maintaining proper calcium levels in the blood and bones.

Adrenal Glands: Stress Response Mediators

The adrenal glands, situated atop the kidneys, produce hormones that help the body respond to stress and regulate metabolism. Key hormones include:

• Cortisol: Regulates metabolism and helps the body respond to stress
• Aldosterone: Regulates blood pressure and electrolyte balance
• Adrenaline (epinephrine): Triggers the “fight-or-flight” response

Pancreas: Blood Sugar Regulator

The pancreas, located behind the stomach, produces hormones that regulate blood sugar levels. The two main hormones are:

• Insulin: Lowers blood sugar levels
• Glucagon: Raises blood sugar levels

Reproductive Glands: Sex Hormone Producers

The ovaries in females and testes in males produce sex hormones that regulate reproductive functions and secondary sexual characteristics. These include:

• Estrogen and progesterone (ovaries)
• Testosterone (testes)

The Hypothalamus: The Endocrine System’s Control Center

The hypothalamus, a small region of the brain, plays a crucial role in regulating the endocrine system. It acts as a link between the nervous system and the endocrine system, coordinating various bodily functions. The hypothalamus performs several important functions:

• Produces and releases hormones that control the pituitary gland
• Regulates body temperature, hunger, thirst, and sleep patterns
• Influences emotional responses and behavior

How does the hypothalamus communicate with the pituitary gland? The hypothalamus produces releasing and inhibiting hormones that travel directly to the pituitary gland through a specialized blood vessel system called the hypophyseal portal system. These hormones then stimulate or inhibit the release of specific pituitary hormones, thus indirectly controlling various endocrine glands and bodily functions.

Hormone Transport and Action: From Gland to Target Cell

Hormones are chemical messengers that travel through the bloodstream to reach their target cells. The process of hormone transport and action involves several steps:

1. Hormone production: Endocrine glands synthesize hormones and store them in secretory vesicles.
2. Hormone release: In response to specific stimuli, the glands release hormones into the bloodstream.
3. Transport: Hormones circulate throughout the body via the bloodstream.
4. Target cell recognition: Hormones bind to specific receptors on or within target cells.
5. Cell response: The binding of hormones to receptors triggers specific cellular responses.

How do hormones affect only specific target cells? Hormones bind to specific receptors that are present only on their target cells. This specificity ensures that hormones elicit responses only in cells that have the appropriate receptors, even though the hormones circulate throughout the entire body.

The Endocrine System’s Role in Homeostasis

The endocrine system plays a crucial role in maintaining homeostasis, the body’s internal balance. It works in conjunction with the nervous system to regulate various physiological processes and adapt to changes in the internal and external environment. Some key areas where the endocrine system contributes to homeostasis include:

• Blood sugar regulation
• Metabolism control
• Calcium balance
• Water and electrolyte balance
• Blood pressure regulation
• Growth and development
• Reproductive functions
• Stress response

How does the endocrine system maintain homeostasis? The endocrine system uses feedback mechanisms to detect changes in the body and respond accordingly. When a hormone’s effects bring the body back to its normal state, it triggers a signal to stop or slow down hormone production. This negative feedback loop helps maintain balance and prevents overcompensation.

Endocrine System Disorders: When Hormones Go Awry

Endocrine disorders occur when glands produce too much or too little of a hormone, or when the body doesn’t respond properly to hormones. Some common endocrine disorders include:

• Diabetes mellitus: Impaired insulin production or function
• Thyroid disorders: Hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid)
• Adrenal insufficiency: Inadequate production of adrenal hormones
• Growth disorders: Excessive or deficient growth hormone production
• Polycystic ovary syndrome (PCOS): Hormonal imbalance affecting female reproductive health

What causes endocrine disorders? Endocrine disorders can result from various factors, including:

• Genetic predisposition
• Autoimmune conditions
• Tumors (benign or malignant) in endocrine glands
• Infections
• Injury to endocrine glands
• Certain medications or treatments

The Endocrine System’s Interaction with Other Organ Systems

The endocrine system works closely with other organ systems to maintain overall health and regulate bodily functions. Some key interactions include:

Endocrine-Nervous System Interaction

The endocrine and nervous systems work together to coordinate rapid and long-term responses to stimuli. The hypothalamus serves as a crucial link between these two systems, integrating nervous system inputs and controlling hormone release.

Endocrine-Cardiovascular System Interaction

Hormones like adrenaline and thyroid hormones influence heart rate and blood pressure. The renin-angiotensin-aldosterone system, involving both endocrine and cardiovascular components, regulates blood pressure and fluid balance.

Endocrine-Digestive System Interaction

Hormones such as insulin, glucagon, and ghrelin play crucial roles in regulating digestion, nutrient absorption, and metabolism. The gut itself produces various hormones that influence appetite and digestion.

Endocrine-Reproductive System Interaction

Sex hormones produced by the endocrine system regulate reproductive functions, including gamete production, pregnancy, and secondary sexual characteristics.

How does the endocrine system coordinate with other systems during stress? During stress, the hypothalamus activates the sympathetic nervous system and triggers the release of stress hormones like cortisol and adrenaline. This coordinated response prepares the body for “fight or flight” by increasing heart rate, blood pressure, and energy availability while suppressing non-essential functions like digestion and reproduction.

The Future of Endocrine Research: Emerging Trends and Potential Breakthroughs

Endocrine research continues to evolve, offering new insights into hormone function and potential treatments for endocrine disorders. Some exciting areas of research include:

• Endocrine disruptors: Investigating the effects of environmental chemicals on hormone function
• Chronobiology: Studying the relationship between hormones and circadian rhythms
• Epigenetics: Exploring how environmental factors influence gene expression in endocrine glands
• Hormone replacement therapies: Developing more targeted and personalized approaches
• Endocrine-immune system interactions: Understanding the role of hormones in immune function

What potential breakthroughs might we see in endocrine research? Some promising areas include:

• Artificial pancreas systems for better diabetes management
• Gene therapy for endocrine disorders
• Novel hormone-based treatments for obesity and metabolic disorders
• Improved diagnostic tools for early detection of endocrine tumors
• Personalized medicine approaches based on individual hormone profiles

As our understanding of the endocrine system continues to grow, we can expect to see significant advancements in the diagnosis, treatment, and prevention of endocrine disorders, ultimately leading to improved health outcomes and quality of life for millions of people worldwide.

10.6: Interaction of Organ Systems

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• Suzanne Wakim & Mandeep Grewal
• Butte College

Teamwork

Every player on a softball team has a special job to perform. Each of the orange team’s players in Figure \(\PageIndex{1}\) has his part of the infield or outfield covered if the ball comes his way. Other players on the orange team cover other parts of the field or pitch or catch the ball. Playing softball clearly requires teamwork. The human body is like a softball team in that regard. All the organ systems of the human body must work together as a team to keep the body alive and well. Teamwork within the body begins with communication.

Figure \(\PageIndex{1}\): Softball

Communication among Organ Systems

Communication among organ systems is vital if they are to work together as a team. They must be able to respond to each other and change their responses as needed to keep the body in balance. Communication among organ systems is controlled mainly by the autonomic nervous system and the endocrine system.

The autonomic nervous system is the part of the nervous system that controls involuntary functions. For example, the autonomic nervous system controls heart rate, blood flow, and digestion. You don’t have to tell your heart to beat faster or to consciously squeeze muscles to push food through the digestive system. In fact, you don’t have to even think about these functions at all. The autonomic nervous system orchestrates all the signals needed to control them. It sends messages between parts of the nervous system and between the nervous system and other organ systems via chemical messengers called neurotransmitters.

Figure \(\PageIndex{2}\): The figure illustrates the hypothalamus, pituitary gland, brain stem, spinal cord, cerebellum, pineal gland, and cerebrum.

The endocrine system is the system of glands that secrete hormones directly into the bloodstream. Once in the blood, endocrine hormones circulate to cells everywhere in the body. The endocrine system is under the control of the hypothalamus, a part of the brain. The hypothalamus secretes hormones that travel directly to cells of the pituitary gland, which is located beneath it. The pituitary gland is the master gland of the endocrine system. Most of its hormones either turn on or turn off other endocrine glands. For example, if the pituitary gland secretes thyroid stimulating hormone, the hormone travels through the circulation to the thyroid gland, which is stimulated to secrete thyroid hormone. Thyroid hormone then travels to cells throughout the body, where it increases their metabolism.

Figure \(\PageIndex{3}\): The image shows a concept map of how the fight-or-flight response occurs. A treat (an attack, harmful event, or threat to survive) leads to the brain processing the signals – beginning in the amygdala, and then the hypothalamus. ACTH (adrenocorticotropic hormone) is released by the pituitary gland. This causes cortisol and adrenaline to be released. The physical effects include heart rate increase, bladder relaxation, tunnel vision, shaking, dilated pupils, flushed face, dry mouth, slowed digestion, and hearing loss.

Examples of Organ System Interactions

An increase in cellular metabolism requires more cellular respiration. Cellular respiration is a good example of organ system interactions because it is a basic life process that occurs in all living cells.

Cellular Respiration

Cellular respiration is the intracellular process that breaks down glucose with oxygen to produce carbon dioxide and energy in the form of ATP molecules. It is the process by which cells obtain usable energy to power other cellular processes. Which organ systems are involved in cellular respiration? The glucose needed for cellular respiration comes from the digestive system via the cardiovascular system. The oxygen needed for cellular respiration comes from the respiratory system also via the cardiovascular system. The carbon dioxide produced in cellular respiration leaves the body by the opposite route. In short, cellular respiration requires at a minimum the digestive, cardiovascular, and respiratory systems.

Fight-or-Flight Response

The well-known fight-or-flight response is a good example of how the nervous and endocrine systems control other organ system responses. The fight-or-flight response begins when the nervous system perceives sudden danger, as shown in Figure \(\PageIndex{2}\). The brain sends a message to the endocrine system (via the pituitary gland) for the adrenal glands to secrete their hormones cortisol and adrenaline. These hormones flood the circulation and affect other organ systems throughout the body, including the cardiovascular, urinary, sensory, and digestive systems. Specific responses include increased heart rate, bladder relaxation, tunnel vision, and a shunting of blood away from the digestive system and toward the muscles, brain, and other vital organs needed to fight or flee.

Digesting Food

Digesting food requires teamwork between the digestive system and several other organ systems, including the nervous, cardiovascular, and muscular systems. When you eat a meal, the organs of the digestive system need more blood to perform their digestive functions. Food entering the digestive systems causes nerve impulses to be sent to the brain; in response, the brain sends messages to the cardiovascular system to increase heart rate and dilate blood vessels in the digestive organs. Food passes through the organs of the digestive tract by rhythmic contractions of smooth muscles in the walls of the organs, so the muscular system is also needed for digestion. After food is digested, nutrients from the food are absorbed into the blood of the vessels lining the small intestine. Any remaining food waste is excreted through the large intestine.

Playing Softball

The men playing softball in Figure \(\PageIndex{1}\) are using multiple organ systems in this voluntary activity. Their nervous systems are focused on observing and preparing to respond to the next play. Their other systems are being controlled by the autonomic nervous system. Organ systems they are using include the muscular, skeletal, respiratory, and cardiovascular systems. Can you explain how each of these organ systems is involved in playing softball?

Feature: Reliable Sources

Teamwork among organ systems allows the human organism to work like a finely tuned machine. Or at least it does until one of the organ systems fails. When that happens, other organ systems interacting in the same overall process will also be affected. This is especially likely if the system affected plays a controlling role in the process. An example is type 1 diabetes. This disorder occurs when the pancreas does not secrete the endocrine hormone insulin. Insulin normally is secreted in response to an increasing level of glucose in the blood, and it brings the level of glucose back to normal by stimulating body cells to take up insulin from the blood.

Learn more about type 1 diabetes. Use several reliable Internet sources to answer the following questions:

1. What causes the endocrine system to fail to produce insulin in type 1 diabetes?
2. Which organ systems are affected by high blood glucose levels if type 1 diabetes is not controlled? What are some of the specific effects?
3. How can blood glucose levels be controlled in patients with type 1 diabetes?

Review

1. What is the autonomic nervous system?
2. How do the autonomic nervous system and endocrine system communicate with other organ systems so the systems can interact?
3. Explain how the brain communicates with the endocrine system.
4. What is the role of the pituitary gland in the endocrine system?
5. Identify organ systems that play a role in cellular respiration.
6. How does the hormone adrenaline prepare the body to fight or flee? What specific physiological changes does it bring about?
7. Explain the role of the muscular system in the digestion of food.
8. Describe how three different organ systems are involved when a player makes a particular play in softball, such as catching a fly ball.
9. True or False. The autonomic nervous system controls conscious movements.
10. True or False. Hormones travel throughout the body.
11. True or False. The pituitary gland directly secretes thyroid hormone.
12. What are two types of molecules that the body uses to communicate between organ systems?
13. Explain why hormones can have such a wide variety of effects on the body.
14. Heart rate can be affected by:
    1. Hormones
    2. Neurotransmitters
    3. The fight-or-flight response
    4. All of the above
15. Which gland secretes the hormone cortisol?

Explore More

https://bio.libretexts.org/link?16779#Explore_More

Without the muscles lining the GI tract, you would be unable to digest food. Watch this short animation of food moving through the GI tract. It illustrates very clearly the necessary interaction of the muscular and digestive systems in the digestive process.

Attributions

1. Marines play softball, public domain
2. Brain by National Cancer Institute, released into the public domain via Wikimedia Commons
3. Fight or Flight Response by Jvnkfood (original), converted to PNG and reduced to 8-bit by Pokéfan95, licensed CC BY 4.0 via Wikimedia Commons
4. Text adapted from Human Biology by CK-12 licensed CC BY-NC 3.0

This page titled 10.6: Interaction of Organ Systems is shared under a CK-12 license and was authored, remixed, and/or curated by Suzanne Wakim & Mandeep Grewal via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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Anatomy and Physiology, Regulation, Integration, and Control, The Endocrine System

By the end of this section, you will be able to:

• Identify the three major classes of hormones on the basis of chemical structure
• Compare and contrast intracellular and cell membrane hormone receptors
• Describe signaling pathways that involve cAMP and IP3
• Identify several factors that influence a target cell’s response
• Discuss the role of feedback loops and humoral, hormonal, and neural stimuli in hormone control

Although a given hormone may travel throughout the body in the bloodstream, it will affect the activity only of its target cells; that is, cells with receptors for that particular hormone. Once the hormone binds to the receptor, a chain of events is initiated that leads to the target cell’s response. Hormones play a critical role in the regulation of physiological processes because of the target cell responses they regulate. These responses contribute to human reproduction, growth and development of body tissues, metabolism, fluid, and electrolyte balance, sleep, and many other body functions. The major hormones of the human body and their effects are identified in Table 17.2.

Endocrine Glands and Their Major Hormones

Table 17. 2

Types of Hormones

The hormones of the human body can be divided into two major groups on the basis of their chemical structure. Hormones derived from amino acids include amines, peptides, and proteins. Those derived from lipids include steroids (Figure 17.3). These chemical groups affect a hormone’s distribution, the type of receptors it binds to, and other aspects of its function.

Figure 17.3 Amine, Peptide, Protein, and Steroid Hormone Structure 

Amine Hormones

Hormones derived from the modification of amino acids are referred to as amine hormones. Typically, the original structure of the amino acid is modified such that a –COOH, or carboxyl, group is removed, whereas the −NH+3−Nh4+

Amine hormones are synthesized from the amino acids tryptophan or tyrosine. An example of a hormone derived from tryptophan is melatonin, which is secreted by the pineal gland and helps regulate circadian rhythm. Tyrosine derivatives include the metabolism-regulating thyroid hormones, as well as the catecholamines, such as epinephrine, norepinephrine, and dopamine. Epinephrine and norepinephrine are secreted by the adrenal medulla and play a role in the fight-or-flight response, whereas dopamine is secreted by the hypothalamus and inhibits the release of certain anterior pituitary hormones.

Peptide and Protein Hormones

Whereas the amine hormones are derived from a single amino acid, peptide and protein hormones consist of multiple amino acids that link to form an amino acid chain. Peptide hormones consist of short chains of amino acids, whereas protein hormones are longer polypeptides. Both types are synthesized like other body proteins: DNA is transcribed into mRNA, which is translated into an amino acid chain.

Examples of peptide hormones include antidiuretic hormone (ADH), a pituitary hormone important in fluid balance, and atrial-natriuretic peptide, which is produced by the heart and helps to decrease blood pressure. Some examples of protein hormones include growth hormone, which is produced by the pituitary gland, and follicle-stimulating hormone (FSH), which has an attached carbohydrate group and is thus classified as a glycoprotein. FSH helps stimulate the maturation of eggs in the ovaries and sperm in the testes.

Steroid Hormones

The primary hormones derived from lipids are steroids. Steroid hormones are derived from the lipid cholesterol. For example, the reproductive hormones testosterone and the estrogens—which are produced by the gonads (testes and ovaries)—are steroid hormones. The adrenal glands produce the steroid hormone aldosterone, which is involved in osmoregulation, and cortisol, which plays a role in metabolism.

Like cholesterol, steroid hormones are not soluble in water (they are hydrophobic). Because blood is water-based, lipid-derived hormones must travel to their target cell bound to a transport protein. This more complex structure extends the half-life of steroid hormones much longer than that of hormones derived from amino acids. A hormone’s half-life is the time required for half the concentration of the hormone to be degraded. For example, the lipid-derived hormone cortisol has a half-life of approximately 60 to 90 minutes. In contrast, the amino acid–derived hormone epinephrine has a half-life of approximately one minute.

Pathways of Hormone Action

The message a hormone sends is received by a hormone receptor, a protein located either inside the cell or within the cell membrane. The receptor will process the message by initiating other signaling events or cellular mechanisms that result in the target cell’s response. Hormone receptors recognize molecules with specific shapes and side groups, and respond only to those hormones that are recognized. The same type of receptor may be located on cells in different body tissues, and trigger somewhat different responses. Thus, the response triggered by a hormone depends not only on the hormone, but also on the target cell.

Once the target cell receives the hormone signal, it can respond in a variety of ways. The response may include the stimulation of protein synthesis, activation or deactivation of enzymes, alteration in the permeability of the cell membrane, altered rates of mitosis and cell growth, and stimulation of the secretion of products. Moreover, a single hormone may be capable of inducing different responses in a given cell.

Pathways Involving Intracellular Hormone Receptors

Intracellular hormone receptors are located inside the cell. Hormones that bind to this type of receptor must be able to cross the cell membrane. Steroid hormones are derived from cholesterol and therefore can readily diffuse through the lipid bilayer of the cell membrane to reach the intracellular receptor (Figure 17.4). Thyroid hormones, which contain benzene rings studded with iodine, are also lipid-soluble and can enter the cell.

The location of steroid and thyroid hormone binding differs slightly: a steroid hormone may bind to its receptor within the cytosol or within the nucleus. In either case, this binding generates a hormone-receptor complex that moves toward the chromatin in the cell nucleus and binds to a particular segment of the cell’s DNA. In contrast, thyroid hormones bind to receptors already bound to DNA. For both steroid and thyroid hormones, binding of the hormone-receptor complex with DNA triggers transcription of a target gene to mRNA, which moves to the cytosol and directs protein synthesis by ribosomes.

Figure 17.4 Binding of Lipid-Soluble Hormones A steroid hormone directly initiates the production of proteins within a target cell. Steroid hormones easily diffuse through the cell membrane. The hormone binds to its receptor in the cytosol, forming a receptor–hormone complex. The receptor–hormone complex then enters the nucleus and binds to the target gene on the DNA. Transcription of the gene creates a messenger RNA that is translated into the desired protein within the cytoplasm.

Pathways Involving Cell Membrane Hormone Receptors

Hydrophilic, or water-soluble, hormones are unable to diffuse through the lipid bilayer of the cell membrane and must therefore pass on their message to a receptor located at the surface of the cell. Except for thyroid hormones, which are lipid-soluble, all amino acid–derived hormones bind to cell membrane receptors that are located, at least in part, on the extracellular surface of the cell membrane. Therefore, they do not directly affect the transcription of target genes, but instead initiate a signaling cascade that is carried out by a molecule called a second messenger. In this case, the hormone is called a first messenger.

The second messenger used by most hormones is cyclic adenosine monophosphate (cAMP). In the cAMP second messenger system, a water-soluble hormone binds to its receptor in the cell membrane (Step 1 in Figure 17.5). This receptor is associated with an intracellular component called a G protein, and binding of the hormone activates the G-protein component (Step 2). The activated G protein in turn activates an enzyme called adenylyl cyclase, also known as adenylate cyclase (Step 3), which converts adenosine triphosphate (ATP) to cAMP (Step 4). As the second messenger, cAMP activates a type of enzyme called a protein kinase that is present in the cytosol (Step 5). Activated protein kinases initiate a phosphorylation cascade, in which multiple protein kinases phosphorylate (add a phosphate group to) numerous and various cellular proteins, including other enzymes (Step 6).

Figure 17.5 Binding of Water-Soluble Hormones Water-soluble hormones cannot diffuse through the cell membrane. These hormones must bind to a surface cell-membrane receptor. The receptor then initiates a cell-signaling pathway within the cell involving G proteins, adenylyl cyclase, the secondary messenger cyclic AMP (cAMP), and protein kinases. In the final step, these protein kinases phosphorylate proteins in the cytoplasm. This activates proteins in the cell that carry out the changes specified by the hormone.

The phosphorylation of cellular proteins can trigger a wide variety of effects, from nutrient metabolism to the synthesis of different hormones and other products. The effects vary according to the type of target cell, the G proteins and kinases involved, and the phosphorylation of proteins. Examples of hormones that use cAMP as a second messenger include calcitonin, which is important for bone construction and regulating blood calcium levels; glucagon, which plays a role in blood glucose levels; and thyroid-stimulating hormone, which causes the release of T₃ and T₄ from the thyroid gland.

Overall, the phosphorylation cascade significantly increases the efficiency, speed, and specificity of the hormonal response, as thousands of signaling events can be initiated simultaneously in response to a very low concentration of hormone in the bloodstream. However, the duration of the hormone signal is short, as cAMP is quickly deactivated by the enzyme phosphodiesterase (PDE), which is located in the cytosol. The action of PDE helps to ensure that a target cell’s response ceases quickly unless new hormones arrive at the cell membrane.

Importantly, there are also G proteins that decrease the levels of cAMP in the cell in response to hormone binding. For example, when growth hormone–inhibiting hormone (GHIH), also known as somatostatin, binds to its receptors in the pituitary gland, the level of cAMP decreases, thereby inhibiting the secretion of human growth hormone.

Not all water-soluble hormones initiate the cAMP second messenger system. One common alternative system uses calcium ions as a second messenger. In this system, G proteins activate the enzyme phospholipase C (PLC), which functions similarly to adenylyl cyclase. Once activated, PLC cleaves a membrane-bound phospholipid into two molecules: diacylglycerol (DAG) and inositol triphosphate (IP₃). Like cAMP, DAG activates protein kinases that initiate a phosphorylation cascade. At the same time, IP₃ causes calcium ions to be released from storage sites within the cytosol, such as from within the smooth endoplasmic reticulum. The calcium ions then act as second messengers in two ways: they can influence enzymatic and other cellular activities directly, or they can bind to calcium-binding proteins, the most common of which is calmodulin. Upon binding calcium, calmodulin is able to modulate protein kinase within the cell. Examples of hormones that use calcium ions as a second messenger system include angiotensin II, which helps regulate blood pressure through vasoconstriction, and growth hormone–releasing hormone (GHRH), which causes the pituitary gland to release growth hormones.

Factors Affecting Target Cell Response

You will recall that target cells must have receptors specific to a given hormone if that hormone is to trigger a response. But several other factors influence the target cell response. For example, the presence of a significant level of a hormone circulating in the bloodstream can cause its target cells to decrease their number of receptors for that hormone. This process is called downregulation, and it allows cells to become less reactive to the excessive hormone levels. When the level of a hormone is chronically reduced, target cells engage in upregulation to increase their number of receptors. This process allows cells to be more sensitive to the hormone that is present. Cells can also alter the sensitivity of the receptors themselves to various hormones.

Two or more hormones can interact to affect the response of cells in a variety of ways. The three most common types of interaction are as follows:

• The permissive effect, in which the presence of one hormone enables another hormone to act. For example, thyroid hormones have complex permissive relationships with certain reproductive hormones. A dietary deficiency of iodine, a component of thyroid hormones, can therefore affect reproductive system development and functioning.
• The synergistic effect, in which two hormones with similar effects produce an amplified response. In some cases, two hormones are required for an adequate response. For example, two different reproductive hormones—FSH from the pituitary gland and estrogens from the ovaries—are required for the maturation of female ova (egg cells).
• The antagonistic effect, in which two hormones have opposing effects. A familiar example is the effect of two pancreatic hormones, insulin and glucagon. Insulin increases the liver’s storage of glucose as glycogen, decreasing blood glucose, whereas glucagon stimulates the breakdown of glycogen stores, increasing blood glucose.

Regulation of Hormone Secretion

To prevent abnormal hormone levels and a potential disease state, hormone levels must be tightly controlled. The body maintains this control by balancing hormone production and degradation. Feedback loops govern the initiation and maintenance of most hormone secretion in response to various stimuli.

Role of Feedback Loops

The contribution of feedback loops to homeostasis will only be briefly reviewed here. Positive feedback loops are characterized by the release of additional hormone in response to an original hormone release. The release of oxytocin during childbirth is a positive feedback loop. The initial release of oxytocin begins to signal the uterine muscles to contract, which pushes the fetus toward the cervix, causing it to stretch. This, in turn, signals the pituitary gland to release more oxytocin, causing labor contractions to intensify. The release of oxytocin decreases after the birth of the child.

The more common method of hormone regulation is the negative feedback loop. Negative feedback is characterized by the inhibition of further secretion of a hormone in response to adequate levels of that hormone. This allows blood levels of the hormone to be regulated within a narrow range. An example of a negative feedback loop is the release of glucocorticoid hormones from the adrenal glands, as directed by the hypothalamus and pituitary gland. As glucocorticoid concentrations in the blood rise, the hypothalamus and pituitary gland reduce their signaling to the adrenal glands to prevent additional glucocorticoid secretion (Figure 17.6).

Figure 17.6 Negative Feedback Loop The release of adrenal glucocorticoids is stimulated by the release of hormones from the hypothalamus and pituitary gland. This signaling is inhibited when glucocorticoid levels become elevated by causing negative signals to the pituitary gland and hypothalamus.

Role of Endocrine Gland Stimuli

Reflexes triggered by both chemical and neural stimuli control endocrine activity. These reflexes may be simple, involving only one hormone response, or they may be more complex and involve many hormones, as is the case with the hypothalamic control of various anterior pituitary–controlled hormones.

Humoral stimuli are changes in blood levels of non-hormone chemicals, such as nutrients or ions, which cause the release or inhibition of a hormone to, in turn, maintain homeostasis. For example, osmoreceptors in the hypothalamus detect changes in blood osmolarity (the concentration of solutes in the blood plasma). If blood osmolarity is too high, meaning that the blood is not dilute enough, osmoreceptors signal the hypothalamus to release ADH. The hormone causes the kidneys to reabsorb more water and reduce the volume of urine produced. This reabsorption causes a reduction of the osmolarity of the blood, diluting the blood to the appropriate level. The regulation of blood glucose is another example. High blood glucose levels cause the release of insulin from the pancreas, which increases glucose uptake by cells and liver storage of glucose as glycogen.

An endocrine gland may also secrete a hormone in response to the presence of another hormone produced by a different endocrine gland. Such hormonal stimuli often involve the hypothalamus, which produces releasing and inhibiting hormones that control the secretion of a variety of pituitary hormones.

In addition to these chemical signals, hormones can also be released in response to neural stimuli. A common example of neural stimuli is the activation of the fight-or-flight response by the sympathetic nervous system. When an individual perceives danger, sympathetic neurons signal the adrenal glands to secrete norepinephrine and epinephrine. The two hormones dilate blood vessels, increase the heart and respiratory rate, and suppress the digestive and immune systems. These responses boost the body’s transport of oxygen to the brain and muscles, thereby improving the body’s ability to fight or flee.

EVERYDAY CONNECTION

Bisphenol A and Endocrine Disruption

You may have heard news reports about the effects of a chemical called bisphenol A (BPA) in various types of food packaging. BPA is used in the manufacturing of hard plastics and epoxy resins. Common food-related items that may contain BPA include the lining of aluminum cans, plastic food-storage containers, drinking cups, as well as baby bottles and “sippy” cups. Other uses of BPA include medical equipment, dental fillings, and the lining of water pipes.

Research suggests that BPA is an endocrine disruptor, meaning that it negatively interferes with the endocrine system, particularly during the prenatal and postnatal development period. In particular, BPA mimics the hormonal effects of estrogens and has the opposite effect—that of androgens. The U.S. Food and Drug Administration (FDA) notes in their statement about BPA safety that although traditional toxicology studies have supported the safety of low levels of exposure to BPA, recent studies using novel approaches to test for subtle effects have led to some concern about the potential effects of BPA on the brain, behavior, and prostate gland in fetuses, infants, and young children. The FDA is currently facilitating decreased use of BPA in food-related materials. Many US companies have voluntarily removed BPA from baby bottles, “sippy” cups, and the linings of infant formula cans, and most plastic reusable water bottles sold today boast that they are “BPA free.” In contrast, both Canada and the European Union have completely banned the use of BPA in baby products.

The potential harmful effects of BPA have been studied in both animal models and humans and include a large variety of health effects, such as developmental delay and disease. For example, prenatal exposure to BPA during the first trimester of human pregnancy may be associated with wheezing and aggressive behavior during childhood. Adults exposed to high levels of BPA may experience altered thyroid signaling and male sexual dysfunction. BPA exposure during the prenatal or postnatal period of development in animal models has been observed to cause neurological delays, changes in brain structure and function, sexual dysfunction, asthma, and increased risk for multiple cancers. In vitro studies have also shown that BPA exposure causes molecular changes that initiate the development of cancers of the breast, prostate, and brain. Although these studies have implicated BPA in numerous ill health effects, some experts caution that some of these studies may be flawed and that more research needs to be done. In the meantime, the FDA recommends that consumers take precautions to limit their exposure to BPA. In addition to purchasing foods in packaging free of BPA, consumers should avoid carrying or storing foods or liquids in bottles with the recycling code 3 or 7. Foods and liquids should not be microwave-heated in any form of plastic: use paper, glass, or ceramics instead.

Endocrine cancer – symptoms, treatment methods, prevention and diagnosis

Endocrinology studies endocrine glands. This is the name of a relatively young field of medicine that studies the human endocrine system and its possible pathologies. Unfortunately, more and more often, oncological diseases are in the field of view of endocrinologists – malignant tumors caused by an atypical growth of the cellular tissue of the glands. Difficulties in their timely diagnosis are associated with the asymptomatic course of the first stages of the disease. Therefore, it is important not to forget about the passage of preventive medical examinations and carefully monitor your health, contacting a doctor at the first sign of malaise.

Causes of endocrine cancer

To date, it has not been possible to establish the causes of endocrine cancer. But experts are ready to name the factors that provoke the pathological conditions of the glands. Among them:

• exposure in areas with high levels of radiation;
• effects of radiotherapy and frequent x-rays;
• iodine deficiency, a sufficient amount of which must be ingested with food;
• bad habits.

The high-risk group includes patients with harmful working conditions, people with a hereditary predisposition, patients over 40 years of age or who have experienced the consequences of prolonged stressful situations. Favorable conditions for the development of cancer of the endocrine glands create chronic diseases of the internal organs, hormonal pathologies and benign formations, the cells of which, under certain conditions, are prone to malignancy.

Types of cancers of the endocrine system

Specialists distinguish the following types of endocrine system cancers:

• thyroid pathology;
• ovarian or testicular cancer;
• neoplasms in the pituitary gland;
• tumor processes in the pancreas and adrenal glands;
• cancers of the thymus.

Symptoms of endocrine cancer

The following should be considered warning signs for the patient:

• intense perspiration;
• sudden changes in psychological and emotional state;
• appetite disorders, insomnia, change in taste habits;
• palpitations, increased pressure;
• severe deterioration of vision;
• difficulty and discomfort when swallowing food.

In what cases it is necessary to see a doctor

In the absence of the above symptoms, the patient should be alerted to the following changes in his own body:

• change in the timbre of the voice towards its coarsening;
• feeling of general weakness and constant fatigue;
• sudden fluctuations in body weight;
• discomfort in the neck;
• decreased potency.

When the first signs of hormonal disorders are detected, it is recommended to immediately seek medical help. According to current statistics, the detection of endocrine cancer in the first or second stage guarantees recovery in more than 99% of cases. Given the asymptomatic course of most types of cancer of the endocrine glands, it becomes clear the importance of their early diagnosis and timely treatment. Qualified specialists of the oncological center “Sofia” in the Central Administrative District of Moscow will conduct an initial examination and refer the patient to the necessary studies to clarify the preliminary diagnosis. Based on the results obtained, an individual course of treatment will be developed, taking into account the characteristics of the body and the age of the visitor. If necessary, other highly specialized specialists will be involved in the work: a gynecologist, gastroenterologist, andrologist, etc.

Methods for diagnosing endocrine cancer

The primary diagnosis of endocrine oncology can be made on the basis of a visual examination and patient complaints of feeling unwell. With a high degree of accuracy to establish the development of the tumor process of the endocrine glands allow:

• blood test for biochemical parameters, which can track any hormonal changes;
• ultrasound, which will accurately indicate the growth of cellular tissue and nodules;
• computed or magnetic resonance imaging to clarify the location of the tumor;
• radioisotope scanning method;
• biopsy of gland tissues, which allows to accurately establish the malignant nature of the tumor.

It is possible to conduct additional specialized studies to control the situation in dynamics and clarify the causes of the oncological process in the endocrine system.

Treatments for human endocrine cancer

Depending on the degree of development and localization of the oncological process, a specialist can choose the appropriate treatment tactics:

• Chemotherapy is the main element of the so-called complex therapy. Effectively fights the spread of metastases, minimizes the risk of recurrence and eliminates the appearance of new nodular formations;
• radiation therapy is based on the introduction of radioactive elements directly into the tumor localization area so that they do not affect healthy tissues. This approach guarantees an accurate impact on the focus of pathology and reduces the risk of side effects;
• removal of the affected organ using modern surgical methods without the formation of sutures and a long period of rehabilitation;
• cryotherapy involves freezing tumors with liquid nitrogen through a special probe. After the course, additional treatment is recommended to remove metastases.

A prerequisite for successful therapy is lifelong use of hormonal drugs by the patient. They stabilize the hormonal background, which positively affects the condition and performance of internal systems and organs.

Measures to prevent cancer of the endocrine system

The most effective measures to prevent hormonal disorders and the development of oncology of the endocrine system are:

timely preventive examination in a medical center with a good reputation.

In addition, regular physical activity, weight control and a complete rejection of bad habits that destroy the body are important.

How to make an appointment with a specialist at the oncological center “Sofia”

To undergo an examination and get a consultation with an oncologist, you can call +7 (495) 995-00-34 (24 hours a day) or fill out an online appointment form on the website. Address: Moscow, Central Administrative District, 2nd Tverskoy-Yamskoy per., 10.

Endocrinologist in Ufa

Services and prices What do we treat? Promotions Reviews

EndocrinologyWhat do we treat?Services and pricesPromotionsReviews

Services and prices

Appointment with an endocrinologist

Primary appointment with an endocrinologist

1 300 ₽

Repeated appointment with an endocrinologist (within 4 months after the initial appointment)

1,100 ₽

Cytological examination (1 glass, 1 formation, 1 node)

400 ₽

Weight problems

Primary appointment with an endocrinologist

1 300 ₽

Repeated appointment with an endocrinologist

1 100 ₽

Sports profile

Primary appointment with an endocrinologist

1 300 ₽

Repeated appointment with an endocrinologist

1 100 ₽

About referral

Diseases of the endocrine system do not have a bright and rapidly progressive clinical picture and often occur without noticeable symptoms, which reduces the chances of successful treatment. In order to timely identify the disease and receive the necessary therapy, it is necessary to periodically check with an endocrinologist. A highly qualified and experienced specialist is able, already at the first appointment, to detect signs that indicate a disruption in the functioning of the organs of the endocrine system.

What is included in the endocrine system

Growth, procreation, emotional reactions and other important processes in the body are provided by the work of the organs of the endocrine system. It includes the following components:

• adrenal glands;

• thyroid;

• parathyroid gland;

• pancreas;

• pituitary and hypothalamus;

• gonads.

Our organs produce hormones that allow organs to communicate with each other. In case of violation of this function, endocrine diseases begin to develop, which reduce the standard of living and can lead to various serious complications.

Signs of endocrine pathology

The following symptoms should be the reason for a visit to an endocrinologist:

If pregnancy is planned, the child should also visit an endocrinologist to prevent health problems. For patients older than 50 years, regular examination by a specialist will help control age-related changes.

Diagnosis

At the first appointment, the doctor collects data and asks about the symptoms that bother the patient. He also palpates the thyroid gland to detect enlargement and the presence of nodules. In some cases, it is required to take tests or conduct studies (for example, ultrasound of the thyroid gland).

It is good to know what questions the doctor will ask. First of all, they ask about the time of onset and the nature of the symptoms. This is followed by questions about diseases that the patient had before (chickenpox, a cold). A lot of attention is paid to heredity – the presence of problems with the endocrine system in one of the relatives increases the likelihood that the patient is predisposed to this.

After receiving all the necessary information, the endocrinologist prescribes the appropriate therapy.

We strongly recommend to refrain from self-treatment. It is possible to make a correct diagnosis and select an effective treatment only if you have the required qualifications and experience. Ignoring this can seriously worsen your condition.

Appointment of pregnant women

For pregnant women, an appointment with an endocrinologist consists in probing the thyroid gland and prescribing tests. After receiving the results, the woman again goes to the doctor, who informs the patient about her condition and gives recommendations.

In the presence of diabetes, a visit to the endocrinologist is mandatory, as the disease can affect the course of pregnancy and the health of the child. The doctor will monitor fluctuations in blood sugar levels. In the event of a pathology, this will allow you to deal with it in a timely manner.

Treatment

Endocrine diseases affect the functioning of the whole organism, since they most often affect the functioning of internal organs. Due to these diseases, problems are observed not only with physical development, but also with the state of the psyche.

An endocrinologist uses a holistic approach, combining effective, gentle and individual treatments, including physiotherapy, diet therapy and drug treatment.

What do we treat?

Clinic doctors

Abdullina Guzel Albertovna

Endocrinologist

Promotions

Check-up “Recovery after childbirth”

Check-up “Recovery after childbirth”

Reviews

I want to thank the kind and sympathetic doctor Abdullina Guzel Albertovna, endo doctor crinologist for such a warm welcome in the clinic. I was able to ask her all the questions I was interested in about the nodes in the thyroid gland.