Hormone Production – Biology Online Tutorial

Biology Tutorials > Control of Growth & Development > Hormone Production

Negative feedback in the pituitary thyroid axis

Table of Contents

Reviewed by: Mary Anne Clark, Ph.D.

Hormones are chemical messengers produced by glands in the endocrine system. Endocrine tissues secrete products that are carried to their target cells by the bloodstream or other tissue fluids. Hormones activate their target cells by binding to receptors in the target cell membrane. Human hormones are in three general categories: steroids, amino acid derivatives, and peptide hormones. Cortisone and estrogen are steroid hormones, epinephrine and thyroxine are amino acid derivatives and insulin and growth hormone are polypeptides.

Hypothalamus and the Pituitary Gland

Many hormones are regulated through the pituitary gland and the hypothalamus. The hypothalamus is a small region at the base of the brain and the pituitary hangs just below it. See the location of the hypothalamus and pituitary in the image above. The hypothalamus secretes releasing hormones that instruct the anterior pituitary gland to secrete certain hormones. One of the hormones regulated by this hypothalamus-pituitary axis is thyroxine, one of the thyroid hormones. Interactions between the thyroid, pituitary, and hypothalamus are illustrated in the image at the top of this page. The hypothalamus produces a thyrotropin-releasing hormone (TRH), which activates the secretion of the thyroid-stimulating hormone (TSH) from the anterior pituitary. The TSH stimulates the release of thyroid hormones from the thyroid gland. The thyroid hormones in turn feed back to suppress both pituitary and hypothalamus hormone production. Both the hypothalamus and the thyroid also produce hormones of their own, e.g. growth hormone from the anterior pituitary and the antidiuretic hormone from the hypothalamus.

Note: The anterior and posterior pituitary are found together, but originate as separate structures. The posterior pituitary is part of the hypothalamus and stores some hypothalamic hormones. The anterior pituitary is derived from the roof of the mouth but migrates to the brain during early development.

• In Figure 1 above, the releasing hormone from the hypothalamus finds its target tissue in the anterior pituitary. It binds to the receptor where a chemical messenger instructs the cell to release the pituitary hormone.
• The secreted pituitary hormone will instruct the target tissue to release its product. Endocrine glands regulated by the hypothalamus and anterior pituitary in this way include the adrenal cortex, the thyroid, and the testes and ovaries.

Hormone Use

Some of the uses to which hormones are put in humans are the following:

Insulin and glucagon are peptide hormones produced by islet cells in the pancreas and regulate blood sugar concentration. Insulin lowers the blood sugar by stimulating the uptake of sugar into various cells, while glucagon raises blood sugar by stimulating the release of glucose from glycogen stored in the liver.

Thyroid hormones are amino acid derivatives produced by the thyroid gland and help to regulate metabolism.

Estrogen, progesterone and testosterone are steroid hormones produced by the ovaries and testes. They regulate male and female sex characteristics, egg and sperm production, and pregnancy

Cortisone is a corticosteroid hormone produced by the adrenal cortex and helps to mediate stress responses.

Epinephrine (adrenalin) is an amino acid derivative produced by the adrenal medulla and mediates the “fight or flight” response to dangerous situations.

Growth hormone is a peptide hormone produced by the anterior pituitary.  It stimulates cell growth and reproduction and also increases metabolism.

Prolactin is a peptide hormone made by the anterior pituitary and stimulates milk production during breast-feeding

ADH, the antidiuretic hormone, is a peptide hormone produced by the hypothalamus and regulates the amount of water reabsorbed by the kidneys.

The next tutorial investigates the use of these hormones in animals with successive pages studying plant hormones.

Credit: 7activestudio

Quiz

Choose the correct word/phrases inside the parenthesis to complete the text.

Hormones are produced by the glands in the (circulatory system/endocrine system).

They are released to reach the target cells. They bind to the receptors in the (cell wall/cell membrane).

In humans, there are three general categories of hormones. They are peptide hormones, amino acid derivatives, and (nucleic acids/steroids).

An example of hormone is (growth hormone/cortisone) that is involved in regulating growth.

Another is (cortisone/epinephrine) that is released by the adrenal medulla during “fight or flight” response.

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Biology Tutorials > Control of Growth & Development > Hormone Production

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The Endocrine System | Introduction to Psychology

Learning Objectives

• Describe the endocrine system and explain its primary responsibilities within the body

The endocrine system consists of a series of glands that produce chemical substances known as hormones (Figure 1). Like neurotransmitters, hormones are chemical messengers that must bind to a receptor in order to send their signal. However, unlike neurotransmitters, which are released in close proximity to cells with their receptors, hormones are secreted into the bloodstream and travel throughout the body, affecting any cells that contain receptors for them. Thus, whereas neurotransmitters’ effects are localized, the effects of hormones are widespread. Also, hormones are slower to take effect, and tend to be longer lasting.

Figure 1. The major glands of the endocrine system are shown.

The study of psychology and the endocrine system is called behavioral endocrinology, which is the scientific study of the interaction between hormones and behavior. This interaction is bidirectional: hormones can influence behavior, and behavior can sometimes influence hormone concentrations. Hormones regulate behaviors such as aggression, mating, and parenting of individuals. Hormones are involved in regulating all sorts of bodily functions, and they are ultimately controlled through interactions between the hypothalamus (in the central nervous system) and the pituitary gland (in the endocrine system). Imbalances in hormones are related to a number of disorders. This section explores some of the major glands that make up the endocrine system and the hormones secreted by these glands.

Major Glands

The pituitary gland descends from the hypothalamus at the base of the brain, and acts in close association with it. The pituitary is often referred to as the “master gland” because its messenger hormones control all the other glands in the endocrine system, although it mostly carries out instructions from the hypothalamus. In addition to messenger hormones, the pituitary also secretes growth hormone, endorphins for pain relief, and a number of key hormones that regulate fluid levels in the body.

Located in the neck, the thyroid gland releases hormones that regulate growth, metabolism, and appetite. In hyperthyroidism, or Grave’s disease, the thyroid secretes too much of the hormone thyroxine, causing agitation, bulging eyes, and weight loss. In hypothyroidism, reduced hormone levels cause sufferers to experience tiredness, and they often complain of feeling cold. Fortunately, thyroid disorders are often treatable with medications that help reestablish a balance in the hormones secreted by the thyroid.

The adrenal glands sit atop our kidneys and secrete hormones involved in the stress response, such as epinephrine (adrenaline) and norepinephrine (noradrenaline). The pancreas is an internal organ that secretes hormones that regulate blood sugar levels: insulin and glucagon. These pancreatic hormones are essential for maintaining stable levels of blood sugar throughout the day by lowering blood glucose levels (insulin) or raising them (glucagon). People who suffer from diabetes do not produce enough insulin; therefore, they must take medications that stimulate or replace insulin production, and they must closely control the amount of sugars and carbohydrates they consume.

The gonads secrete sexual hormones, which are important in reproduction, and mediate both sexual motivation and behavior. The female gonads are the ovaries; the male gonads are the testis. Ovaries secrete estrogens and progesterone, and the testes secrete androgens, such as testosterone.

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Dig Deeper: Athletes and Anabolic Steroids

Although it is against most laws to do so, many professional athletes and bodybuilders use anabolic steroid drugs to improve their athletic performance and physique. Anabolic steroid drugs mimic the effects of the body’s own steroid hormones, like testosterone and its derivatives. These drugs have the potential to provide a competitive edge by increasing muscle mass, strength, and endurance, although not all users may experience these results. Moreover, the use of performance-enhancing drugs (PEDs) does not come without risks. Anabolic steroid use has been linked with a wide variety of potentially negative outcomes, ranging in severity from largely cosmetic (acne) to life-threatening (heart attack). Furthermore, the use of these substances can result in profound changes in mood and can increase aggressive behavior (National Institute on Drug Abuse, 2001).

Baseball player Alex Rodriguez (A-Rod) has been at the center of a media storm regarding his use of illegal PEDs. Rodriguez’s performance on the field was unparalleled while using the drugs; his success played a large role in negotiating a contract that made him the highest-paid player in professional baseball. Although Rodriguez maintains that he had not used PEDs, he was suspended for the entire 2014 regular season and postseason, costing him more than 20 million dollars in earnings (Gaines, 2013). What are your thoughts on athletes and doping? Do you believe the use of PEDs should be banned? Why or why not? What advice would you give an athlete who was considering using PEDs?

Hormones and Behavior

How might behaviors affect hormones? Extensive studies on male zebra finches and their singing (only male finches sing) demonstrate that the hormones testosterone and estradiol affect their singing, but the reciprocal relation also occurs; that is, behavior can affect hormone concentrations. For example, the sight of a territorial intruder may elevate blood testosterone concentrations in resident male birds and thereby stimulate singing or fighting behavior. Similarly, male mice or rhesus monkeys that lose a fight decrease circulating testosterone concentrations for several days or even weeks afterward. Comparable results have also been reported in humans. Testosterone concentrations are affected not only in humans involved in physical combat, but also in those involved in simulated battles. For example, testosterone concentrations were elevated in winners and reduced in losers of regional chess tournaments.

People do not have to be directly involved in a contest to have their hormones affected by the outcome of the contest. Male fans of both the Brazilian and Italian teams were recruited to provide saliva samples to be assayed for testosterone before and after the final game of the World Cup soccer match in 1994. Brazil and Italy were tied going into the final game, but Brazil won on a penalty kick at the last possible moment. The Brazilian fans were elated and the Italian fans were crestfallen. When the samples were assayed, 11 of 12 Brazilian fans who were sampled had increased testosterone concentrations, and 9 of 9 Italian fans had decreased testosterone concentrations, compared with pre-game baseline values (Dabbs, 2000).

In some cases, hormones can be affected by anticipation of behavior. For example, testosterone concentrations also influence sexual motivation and behavior in women. In one study, the interaction between sexual intercourse and testosterone was compared with other activities (cuddling or exercise) in women (van Anders, Hamilton, Schmidt, & Watson, 2007). On three separate occasions, women provided a pre-activity, post-activity, and next-morning saliva sample. After analysis, the women’s testosterone was determined to be elevated prior to intercourse as compared to other times. Thus, an anticipatory relationship exists between sexual behavior and testosterone. Testosterone values were higher post-intercourse compared to exercise, suggesting that engaging in sexual behavior may also influence hormone concentrations in women.

Link to Learning

Learn more about endocrinology from The Noba Psychology article, “Hormones and Behavior.”

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Think It Over

Given the negative health consequences associated with the use of anabolic steroids, what kinds of considerations might be involved in a person’s decision to use them?

Glossary

adrenal gland: sits atop our kidneys and secretes hormones involved in the stress response

diabetes: disease related to insufficient insulin production

endocrine system: series of glands that produce chemical substances known as hormones

gonad: secretes sexual hormones, which are important for successful reproduction, and mediate both sexual motivation and behavior

hormone: chemical messenger released by endocrine glands

pancreas: secretes hormones that regulate blood sugar

pituitary gland: secretes a number of key hormones, which regulate fluid levels in the body, and a number of messenger hormones, which direct the activity of other glands in the endocrine system

thyroid: secretes hormones that regulate growth, metabolism, and appetite

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When a child needs to visit an endocrinologist

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Article author:

Soboleva Ksenia Andreevna

, pediatrician

It consists of endocrine glands that secrete hormones – chemicals that regulate the functioning of organs and systems. These include: pituitary gland, thyroid gland, adrenal glands and gonads, pancreas. Together they control the work of the entire child’s body and influence the growth, mental and physical development of the baby. This is a very complex system that regulates many body processes. In this regard, it is obvious that its normal functioning is important for any organism, especially during the period of intensive growth and development, which occurs in childhood and adolescence.

Unfortunately, the pathology of the endocrine system in children very often goes unnoticed, as a rule, the symptoms are so blurred that they can be easily explained by normal age-related changes. In about 80% of cases, hormonal problems masquerade as other conditions. When should you take your child to see a specialist?

Mandatory observation of the child by an endocrinologist is necessary if the family has such diseases as diabetes, thyroid disease, obesity and other endocrine disorders. In addition, an appeal to an endocrinologist is advisable during puberty, to assess height, weight, sexual development, and the state of the thyroid gland.

At the root of any pathology of the endocrine system is an excess or lack of production of any hormone. What leads to failure of the endocrine glands? Why do some people produce hormones in the right amount, while others do not? Why don’t hormones get to the right places? Currently, scientists cannot reliably answer these questions. Poor ecology, malnutrition, genetic predisposition, trauma and brain tumors, viral and bacterial diseases – any of these factors can lead to a malfunction in the endocrine system of the body.

According to the National Research Center for Children’s Health of the Russian Academy of Medical Sciences, the proportion of endocrine diseases in children aged 8 to 15 years has increased significantly over the past 20 years. This is due to a change in the lifestyle of children and adolescents – it has become less mobile, a large amount of fast food, soda and sugar-containing products are eaten, the air in cities is heavily polluted. All of the above factors increase the risk of endocrine disruption and can lead to diseases such as diabetes mellitus, hypothyroidism, obesity, and pituitary dysfunction and other disorders of the endocrine system.

So, what should alert a parent?

If a child suddenly has:

• intense thirst,
• excessive sweating,
• change in sweat odor,
• increased frequency of urination in the absence of an infectious agent,
• Persistent chills without signs of infectious disease,
• sudden weight fluctuations in any direction,
• stunting or vice versa too fast growth,
• appearance of stretch marks on the skin,
• premature appearance of secondary sexual characteristics,
• abdominal pain without visible provoking factors,
• Appetite races,
• causeless mood changes,
• severe fatigue,
• poor exercise tolerance,
• emotional lability (unreasonable tearfulness, outbursts of anger),
• severe dryness of the skin (skin remains dry after intense physical activity),
• pale skin,
• brittle nails and hair, hair loss,
• drop in academic performance under the condition of previous diligence

– all this may be the first signs of disruption of the endocrine glands.

If your child has at least two of them, take him to an endocrinologist.

Making an appointment with a pediatric endocrinologist

For more details, consult a qualified specialist at the Family Clinic.

To find out the prices for an appointment with a pediatric endocrinologist or other questions, follow the link below:

Tags EndocrinologistHormones

10 symptoms of hormonal imbalance and what to do about it

Hormonal imbalances can cause a range of unwanted symptoms, from fatigue or weight gain to itchy skin or a bad mood.

Hormones are chemicals produced by glands in the endocrine system and released into the bloodstream. An imbalance occurs when there is too much or too little hormone.

Your hormones are important in regulating many different bodily processes, including appetite and metabolism, sleep cycles, reproductive cycles and sexual function, body temperature, and mood.

Therefore, it is not surprising that even the slightest imbalance can have a noticeable impact on your overall health and well-being.

Hormone levels naturally fluctuate at different stages of life, most notably during puberty and in women during the menstrual cycle, pregnancy, and menopause. They can also be affected by lifestyle and certain diseases.

It is important to notice any symptoms and be examined by a specialist in order to receive the appropriate treatment – medical or invasive, or simply lifestyle changes – to restore balance and your health.

1. Mood swings. The female sex hormone estrogen affects neurotransmitters in the brain, including serotonin (a mood-enhancing chemical). Fluctuations in estrogen levels can cause premenstrual syndrome (PMS) or depressed mood during perimenopause (the phase before menstruation stops completely) and menopause.

   What to do: If sadness or anxiety is interfering with daily life, diet or lifestyle changes such as exercise, quitting smoking and alcohol, and herbal remedies or hormone replacement therapy (HRT) may help. All of these can improve your mood.

2. Heavy or painful periods: if accompanied by other symptoms such as abdominal pain, frequent need to urinate, lower back pain, constipation and painful intercourse, then you may have fibroids. A fibroid is a non-cancerous growth that develops in or around the uterus. The exact cause of fibroids is unknown, although it is thought to be estrogen-stimulated or simply hereditary.

   What to do: If you have symptoms, talk to your doctor, he will prescribe medicines to reduce fibroids. In severe cases, or if medical treatment does not resolve the problem, surgery may be considered to remove them.

3. Low libido. Low libido is especially common in women going through perimenopause or menopause due to declining levels of estrogen and testosterone (although known as a male hormone, women also have testosterone). Other menopausal symptoms such as night sweats, fatigue, low mood and anxiety can also affect your sex life.

   What to do: If you are going through menopause, you may want to consult with your doctor about using testosterone as part of your HRT. It can improve your libido as well as boost your mood and energy levels. It is given in very low doses as a gel applied to the skin.

4. Insomnia and poor quality sleep. During perimenopause and menopause, the ovaries gradually produce less estrogen and progesterone, which contributes to poor sleep. Decreased estrogen levels can also contribute to night sweats, which disrupt sleep, contribute to fatigue, and lack of energy.

   What to do: The first step is to get an accurate diagnosis. If you are going through perimenopause or menopause, discuss HRT with your doctor, therapy will restore estrogen and progestogen levels. Other things you can do to improve your sleep include sleeping in cotton and cotton linens, keeping your bedroom cool, exercising, and cutting back on alcohol and caffeine.

5. Unexplained weight gain. Hormonal conditions can cause weight gain, including an underactive thyroid (when it doesn’t produce enough hormones that regulate metabolism), polycystic ovary syndrome (some hormones cause cysts on the ovaries), and menopause (it leads to hormonal changes that can contribute to weight gain).

   What to do: If you’re experiencing unexplained weight gain without any changes to your diet or exercise level, you may want to see your doctor to check for conditions such as thyroid problems or ovarian cysts. If you are going through menopause, you can talk to your doctor to discuss HRT. Some women believe that HRT causes weight gain, but there is no evidence to support this.

6. Skin problems: Chronic acne in adults can be a sign of low estrogen and progesterone levels and high androgenic hormone levels, and may also indicate polycystic ovary syndrome. Similarly, hormonal imbalances during pregnancy or menopause can cause itchy skin, while dry skin is a symptom of menopause or a thyroid problem.

   What to do: If you think a persistent skin problem is caused by hormonal imbalance, you may want to consult with a specialist to diagnose and treat the underlying problem.

7. Fertility problems: Hormonal imbalance is one of the leading causes of female infertility, and as hormone levels change, a woman’s fertility naturally declines after age 35. High levels of follicle-stimulating hormone (FSH) can reduce a woman’s chances of getting pregnant, while low levels of luteinizing hormone (LH), which stimulates the ovaries to release an egg and start producing progesterone, can also cause fertility problems. Early menopause and other hormonal conditions such as PCOS affect your fertility.

   What to do: Your health care provider may take a blood test to check your FSH and LH levels and if you’ve been trying to get pregnant for a year or less. If you are over 35, you may want to see a fertility specialist to diagnose the root cause of your difficulty conceiving.

8. Headaches: Many women suffer from headaches due to hormonal changes during the menstrual cycle, pregnancy or menopause.

   What to do: Keeping a symptom diary will help you and your doctor identify the causes of your headaches. Eating small, frequent snacks and keeping a regular sleep schedule may help. If you have regular attacks, your doctor may prescribe migraine medication, birth control pills, or HRT.