About all

Hormones location: The Endocrine System – PMC

Brain Hormones | Endocrine Society

The pituitary gland and the hypothalamus—are located in or near the brain. The hypothalamus and the pituitary gland are like orchestra conductors. Their job is to tell other endocrine glands throughout the body to make the hormones that affect and protect every aspect of your health. Found deep inside the brain, the hypothalamus produces releasing and inhibiting hormones and controls the “master gland”— the pituitary. Together, the hypothalamus and pituitary tell the other endocrine glands in your body to make the hormones that affect and protect every aspect of your health.

Pineal glands is important for the sleep cycle regulation of female reproductive hormone associated with fertility and menstrual cycle. Researchers are still learning about the potential functions of the pineal gland and the hormone melatonin. Other hormones produced in the brain are:

  • Antidiuretic Hormone (ADH) – also called vasopressin, which regulate sodium levels and water balance.  Lack of ADH causes increased urination and thirst, a condition that is called diabetes insipidus.
  • Thyrotropin-releasing hormone (TSH) is produced in the hypothalamus and stimulates the release stimulates the thyroid gland to produce thyroid hormones. Too much TSH is rare and will cause hyperthyroidism (too much thyroid hormone). Lack of TSH results in hypothyroidism (not enough thyroid hormone). 

Hypothalamus Hormones

Kisspeptin, made in the hypothalamus, is an important hormone that starts the release of several other hormones. Also called metastin, this interesting hormone is connected to puberty and may also help stop the spread of cancer.

What Does Kisspeptin Do?

Kisspeptin enters into receptor sites in the pituitary gland, starting a reaction that causes the gland to release neurotransmitters. Those neurotransmitters then signal the release of luteinizing hormone and follicle stimulating hormone. These hormones have a role to play in the production of testosterone and oestradiol. Without kisspeptin, this entire chain reaction would be damaged.

Kisspeptin has a secondary function that is not related to hormones. Its original name, metastin, points to its ability to prevent the spread of cancer in the body.Kisspeptin is released in conjunction with two other hormones: dynorphin and neurokinin B. These two hormones are not understood well, but early research indicates they may have a role in causing the release of kisspeptin.

Potential Problems with Kisspeptin Levels

Having high levels of kisspeptin is not related to any conditions or symptoms, although preliminary research indicates that high kisspeptin levels in childhood can lead to early puberty, but this has not yet been proven. Research has also found that women have high levels of kisspeptin in their blood streams during pregnancy, but why this occurs is not yet understood.

Improper kisspeptin function or low kisspeptin levels, however, can cause problems. Specifically, inadequate function of this hormone can cause infertility by preventing menstruation in women. Sometimes, just one injection of kisspeptin can trigger ovulation, which can allow for artificial insemination and in vitro fertilization using the woman’s eggs.

In adolescents, low kisspeptin levels or poor kisspeptin signaling can delay or prevent the onset of puberty. Other problems connected to high or low kisspeptin levels are still being discovered and researched.

If you are struggling with fertility, kisspeptins may be one of the reasons. Talk to your healthcare provider about your kisspeptin levels, and learn whether kisspeptin treatment could potentially help.

Oxytocin is a hormone produced by the hypothalamus and secreted by the pituitary gland. This important hormone plays a crucial role in the childbirth process and also helps with male reproduction. Understanding oxytocin will help you take better care of your health and lead you toward a better understanding of how your body functions.

In women, oxytocin is responsible for signaling contractions of the womb during labor. The hormone stimulates the uterine muscles to contract, so labor begins. It also increases the production of prostaglandins, which move labor along and increases the contractions even more. Because of this effect, synthetic oxytocin (pitocin) is sometimes used to induce a woman to start labor if she cannot start naturally, or it can be given to make contractions stronger if a woman’s labor is slowing.

Once the baby is born, oxytocin promotes lactation by moving the milk into the breast. When the baby sucks at the mother’s breast, oxytocin secretion causes the milk to release so the baby can feed. At the same time, oxytocin is released into the brain to stimulate further oxytocin production. Once the baby stops feeding, the production of the hormone stops until the next feeding.

For men, oxytocin function is less important, but it does have a role to play in moving sperm. It also appears to affect the production of testosterone in the testes.

Studies of oxytocin also have found that it is an important chemical messenger that controls some human behaviors and social interaction. It is oxytocin that triggers the bond between a mother and an infant, and it may also play a role in recognition, sexual arousal, trust, and anxiety. Some research shows that the hormone may affect addiction and stress as well.

How is Oxytocin Production Controlled?

Oxytocin production is controlled by a positive feedback mechanism. This mechanism allows the release of the oxytocin hormone when a trigger occurs. The hormone then causes an action in the body, such as the letdown of milk or the start of labor contractions, which signals more production of oxytocin. The feedback cycle continues until the action, such as childbirth or feeding the baby, is complete.

Problems with Oxytocin Production

High and low oxytocin levels are possible, but research has not yet found any implications of these conditions. Men with high levels of oxytocin sometimes develop benign prostatic hyperplasia, or the enlarging of the prostate gland. This condition can cause urinary complaints. A lack of oxytocin can prevent the milk letdown reflex and make breastfeeding difficult. Low oxytocin levels have also been linked to depression, but using oxytocin to treat mental health conditions has not yet been studied sufficiently.

If you have further questions about oxytocin, or simply want to ensure that your hormones are functioning properly, you need the services of an endocrinologist.

Gonadotrophin-releasing hormone (GnRH) is produced from cells in the hypothalamus. It is then released into small blood vessels that carry the hormone to the pituitary gland. As a consequence, the pituitary gland produces luteinizing hormone (LH) and follicle-stimulating (FSH) hormones. These hormones, LH and FSH, are essential to male and female reproductive health. GnRH causes the pituitary gland to secrete LH and FSH.

In childhood, GnRH levels are low. As puberty begins, GnRH levels start to rise. When the testes and ovaries are fully developed, GnRH, LH, and FSH production are controlled by the levels of testosterone and female sex hormones (estrogen and progesterone). In women, FSH encourages eggs to grow in the ovaries. Leading to the production of estrogen, which signals to the pituitary gland to decrease the release of FSH and to produce more LH, causing ovulation and FSH and LH levels to drop. In men, GnRH stimulates the production of LH from the pituitary gland. LH attaches to receptor cells in the testes, which starts the production of sperm cells.

What Problems Can Occur with GnRH?

Research is still being conducted on the effects of having too much GnRH. In rare cases, pituitary tumors can develop, which increases the production of gonadotropins (LH and FSH), which might cause the body to overproduce testosterone and estrogen. If GnRH levels are too low, it often means that a person does not begin puberty. Kallmann’s Syndrome is an condition where gonadotropin levels are low due to inadequate GnRH levels. This condition is more common among men and is accompanied by a decreased sense of smell. Also, damage to the hypothalamus can halt GnRH production. This will also stop the regular production of FSH and LH. This may lead to amenorrhea in women, loss of sperm production in men, and loss of hormones made from the ovaries or testes.

Pineal Hormones

Melatonin is created by the pineal gland in the brain. In a healthy, normally functioning individual, melatonin is released in a rhythmic cycle, with more melatonin produced at night when the light entering the eyes starts to diminish. The bloodstream carries it to the different areas of the body, where receptors pick up the melatonin to signal the need for sleep. 

Melatonin is essential to signaling the relaxation and lower body temperature that help with restful sleep. Levels of melatonin are higher at night, signaling the body that it is time to rest. In animals, the hormone also regulates seasonal biology, such as the reproductive system, winter coat growth, and hibernation behaviors. A connection between melatonin and human reproduction or seasonal cycles has not yet been established. Because it is so connected to sleep, melatonin has been called the “sleep hormone.” However, it is not necessary for sleep, and people can sleep with inadequate levels of melatonin in the body. That said, the secretion of melatonin does allow individuals to sleep better.

Problems Connected with Melatonin

People do not experience problems with melatonin secreted naturally by the body. The amount of melatonin produced by the body, whether low or high, is not associated with any health problems. In fact, in a lifetime, melatonin levels increase and decrease during the various stages of life. Low levels of melatonin do not appear to have any serious effects on health — although it can make sleep difficult to achieve if the levels change.

However, melatonin supplementation as a sleep aid is popular, and sometimes people will take too much melatonin. This can cause drowsiness and a reduced core body temperature. Extremely high levels of melatonin can also contribute to headaches and fatigue. It’s also possible for very large doses of melatonin to affect human reproduction.

If you are considering taking melatonin supplements to help with sleep, consider asking your healthcare provider:

  • How much melatonin do I need?
  • How much melatonin is too much?
  • How long can I take melatonin safely?
  • Is long-term melatonin use dangerous?
How Does the Body Uses Serotonin?

Mood: Serotonin is in the brain. It is thought to regulate mood, happiness, and anxiety. Low levels of serotonin are linked to depression, while increased levels of the hormone may decrease arousal.

Bowel Movements: Serotonin is found in your stomach and intestines. It helps control your bowel movements and function.

Nausea: Serotonin is produced when you become nauseated. Production of serotonin increases to help remove bad food or other substances from the body. It also increases in the blood, which stimulates the part of the brain that controls nausea.

Sleep: Serotonin is responsible for stimulating the parts of the brain that control sleep and waking. Whether you sleep or wake depends on the area is stimulated and which serotonin receptor is used.

Blood Clotting: Serotonin is released to help heal wounds. Serotonin triggers tiny arteries to narrow, which helps forms blood clots.

Bone Health: Having very high levels of serotonin in the bones can lead to osteoporosis, which makes the bones weaker.

Mental Health: Serotonin helps regulate your mood naturally. When your serotonin levels are at a normal level, you should feel more focused, emotionally stable, happier, and calmer.

What Problems are Associated with Low Levels of Serotonin?

Low levels of serotonin are often associated with many behavioral and emotional disorders. Studies have shown that low levels of serotonin can lead to depression, anxiety, suicidal behavior, and obsessive-compulsive disorder. If you are experiencing any of these thoughts or feelings, consult a health care professional immediately. The sooner treatment starts, the faster you’ll see improvements.

What Problems are Associated with High Levels of Serotonin?

Serotonin syndrome can occur when you take medications that increase serotonin action leading to side effects. Too much serotonin can cause mild symptoms such as shivering, heavy sweating, confusion, restlessness, headaches, high blood pressure, twitching muscles, and diarrhea. More severe symptoms include high fever, unconsciousness, seizures, or irregular heartbeat. Serotonin syndrome can happen to anyone, but some people may be at higher risk. You are at a higher risk if you increased the dose of medication that is known to raise serotonin levels or take more than one drug known to increase serotonin. You may also be at risk if you take herbal supplements or an illicit drug known to increase serotonin levels.

If you suspect that your serotonin levels are too high or low, the first step is to speak with a health care professional.

Consider asking your doctor:

  • Is my medication causing serotonin syndrome?
  • If I am experiencing feelings of depression, are my serotonin levels too low?
  • Are my levels of serotonin affecting any other aspects of my health?

Pituitary Hormones

Adrenocorticotropic hormone (ACTH) plays a large role in how your body responds to stress. ACTH is produced in the pituitary gland, its production stimulates the production and release of cortisol from the adrenal gland. After ACTH is made in the pituitary gland, ACTH is released into the bloodstream and travels around the body. Production of ACTH is regulated by corticotrophin-releasing hormone (CRH) from the hypothalamus and cortisol from the adrenal gland. If ACTH levels are low, the hypothalamus releases CRH which is key to the stress hormone system and acts on many areas of the brain such as appetite and memory. Once the CRH is discharged, it triggers the pituitary gland to secrete ACTH.

High levels of ACTH are detected by the adrenal gland, which starts the production of cortisol. When cortisol levels rise in the body, the brain can sense these high levels and the production of the CRH and ACTH decreases. Stress activates ACTH production and increases cortisol levels.

What Problem Can Occur With ACTH?

If too much ACTH is produced, this can lead to high levels of cortisol in the body, also known as Cushing syndrome. The most common cause of increased ACTH production is a benign pituitary tumor.  When this is present, the disorder is called Cushing disease. Other endocrine conditions that may lead to an increase of ACTH include adrenal insufficiency and congenital adrenal hyperplasia.

Having lower than normal ACTH levels in the blood can be a result of other endocrine conditions such as Cushing syndrome or hypopituitarism. 

ACTH Testing
To diagnose these conditions, healthcare providers can order an ACTH blood test. An ACTH test is ordered if a cortisol blood test has abnormal results or if a patient has symptoms of too much or too little cortisol. Analyzing ACTH and cortisol levels together can help identify the different endocrine conditions associated with high and low cortisol levels. To test ACTH levels, healthcare providers may require you to fast overnight and conduct the test early in the morning. This is because ACTH levels are high in the morning and gradually decrease during the day. ACTH is at its lowest level during sleep. 

Human growth hormone (GH) is a substance that controls your body’s growth. GH is made by the pituitary gland, located at the base of the brain. GH helps children grow taller (also called linear growth), increases muscle mass, and decreases body fat. In both children and adults, GH also helps control the body’s metabolism—the process by which cells change food into energy and make other substances that the body needs.

If children or adults have too much or too little GH, they may have health problems. Growth hormone deficiency (too little GH) and some other health problems can be treated with synthetic (manufactured) GH. Sometimes GH is used illegally for non-medical purposes.

How is Growth Hormone Therapy Used?

The U.S. Food and Drug Administration (FDA) has approved GH treatment for certain conditions. GH is available only by prescription and is injected. Synthetic GH seems to be safe and effective when used as prescribed for the FDA-approved conditions.

In children, GH is used to treat:

Growth hormone deficiency
Conditions that cause short stature (being shorter than children of the same age), such as chronic kidney disease, Turner syndrome, and Prader-Willi syndrome

In adults, GH is used to treat:

Growth hormone deficiency
Muscle wasting (loss of muscle tissue) from HIV
Short bowel syndrome

Some companies sell human GH pills or GH releasers, claiming that the pills are “anti-aging” substances. But these substances have not been proven to increase the body’s production of GH or to fight aging, increase muscle, or provide other benefits. GH has no effect if it is taken as a pill because it is inactivated (loses its action) during digestion.

In addition to these uses, doctors outside and a number within the U.S. sometimes prescribe GH for other health problems. (When doctors prescribe medicines for conditions other than the ones officially approved, the process is called “off-label” use.)

If you’re worried about GH deficiency in yourself or a family member, talk with a doctor.

Is Growth Hormone Use Appropriate for Healthy Adults?

Studies of healthy adults taking GH have produced conflicting results. Some short-term studies showed that older adults increased their endurance and strength, with increased muscle and decreased fat mass. But other studies did not show similar benefits. More studies are needed to fully understand the benefits and risks of GH use in healthy adults.

Aside from its use in research studies, prescribing or using GH off-label is illegal in the US. Adults can achieve improved health, body composition, strength, and endurance by following a healthy diet and getting frequent exercise.

How is Growth Hormone Abused?

People sometimes take GH illegally to stop or reverse the effects of aging or to improve athletic performance. Some athletes believe taking GH alone will not achieve the desired results, so they take it along with anabolic (tissue building) steroids in an effort to build muscle, increase strength, and decrease body fat. Some athletes also use insulin to increase the muscular effects of GH, which is a dangerous practice because it lowers blood sugar.

What Are the Risks of Growth Hormone Abuse?

People can experience harmful side effects when they abuse GH. Side effects of short-term use include joint and muscle pain, fluid build-up, and swelling in the joints. If GH is injected with shared needles, people may be exposed to HIV, AIDS, or hepatitis. Taking high doses of GH over a long time may contribute to heart disease.

GH sold illegally may contain unknown and potentially harmful ingredients. For instance, if people take GH derived from human tissue, they risk developing a fatal brain disease called Creutzfeldt-Jakob disease, which is similar to mad cow disease. Consider asking your healthcare provider:

  • Do I (or my child) need human growth hormone treatment for medical reasons?

  • What are the benefits and risks of growth hormone treatment?

  • What are the signs of growth hormone abuse?

  • Should I see an endocrinologist about my condition?

Human Chorionic Gonadotropin (hCG) hormone is important in the early stages of pregnancy. It is produced by cells that are surrounding a growing embryo, which eventually forms the placenta. hCG can be detected in your body as early as 1 week after an egg is fertilized, which forms the basis of most over the counter pregnancy tests. hCG also ensures the corpus luteum, a temporary endocrine gland a woman’s body produces after ovulation, continues to produce progesterone during the first trimester of pregnancy. Low concentrations of hCG  are also produced by the pituitary gland, thus, men and non-pregnant women still have detectable levels of HcG throughout their lives.

The levels of hCG increases every two to three days as your embryo continues to develop. hCG levels peak around the sixth week of pregnancy. Afterwards, hCG will be found in your body, but the levels will begin to decrease. Once the placenta is fully formed, it serves as a source of progesterone production and assistance from hCG to support ovarian function is no longer essential.

What Problems can Occur with hCG?

Very high hCG levels are rare. In these cases, it may be sign of a molar pregnancy, which is an abnormal growth of cells that usually develop in the placenta. In people who are not pregnant, high hCG levels may be due to certain cancers such as breast, kidney, and lung. Low levels of hCG may be a sign of a miscarriage or another problem within the pregnancy, such as the embryo implanting outside of the uterus. Consider asking your healthcare provider:

  • How early can doctors detect my hCG levels?

  • What test is the best way to detect pregnancy?

  • Why is hCG important in the early stages of my pregnancy?

Luteinizing hormone (LH) is produced and released in the anterior pituitary gland. This hormone is considered a gonadotrophic hormone because of its role in controlling the function of ovaries in females and testes in males, which are known as the gonads.

In women, the hormone stimulates the ovaries to produce oestradiol. Two weeks into a woman’s cycle, a surge in luteinizing hormone causes the ovaries to release an egg during ovulation. If fertilization occurs, luteinizing hormone will stimulate the corpus luteum, which produces progesterone to sustain the pregnancy.

For men, luteinizing hormone stimulates the production of testosterone from Leydig cells in the testes. Testosterone, in turn, stimulates sperm production and helps accentuate male characteristics — like a deep voice or growth of facial hair.

What Problems Can Occur With Luteinizing Hormone?

People who have high levels of luteinizing hormone may experience infertility, because the hormone directly impacts the reproductive system. In women, luteinizing hormone levels that are too high are often connected to polycystic ovary syndrome, which creates inappropriate testosterone levels. Some genetic conditions, like Turner syndrome or Klinefelter syndrome, can cause high levels of the hormone, as well. People with these conditions are often unable to reproduce.

Low levels of luteinizing hormone can also cause infertility, because insufficient levels will limit the production of sperm or the ovulation process. Too little luteinizing hormone stops ovulation in women or creates a deficiency in gonadotrophin-releasing hormone (GnRH) secretion in men.

If you are struggling with infertility or other reproductive-system complaints, poor luteinizing hormone levels. Consider your healthcare provider:

  • What hormone imbalances could be affecting my fertility?

  • What blood tests should I have to determine the hormones that are not in proper balance?

  • Is there any way to treat these imbalances?

  • How can I support a better hormone balance naturally?

Prolactin, as its name implies, is a hormone that promotes lactation (breast milk production) in mammals and is responsible for a number of other functions and systems. Prolactin is created in the front portion of the pituitary gland in your brain, as well as in the uterus, brain, breasts, prostate, adipose tissue, skin, and immune cells.

Prolactin (also known as luteotropin) function is still being studied, but research seems to show a variety of purposes for this hormone. For instance, it also regulates behavior, the immune system, metabolism, reproductive systems, and many different bodily fluids. This makes it a crucial hormone for overall health and well-being, for both men and women. Production of prolactin is controlled by two main hormones: dopamine and estrogen. These hormones send a message to the pituitary gland primarily indicating whether to begin or cease the production of prolactin. Dopamine restrains the production of prolactin, while estrogen increases it.

Possible Problems with Prolactin Production

For most people, prolactin does its job without a problem, and few are aware of the impact it has on their health. Yet some people can struggle with prolactin levels, which can cause a variety of problems. Too much prolactin in the blood causes hyperprolactinemia, a condition that can lead to menstrual disturbances, estrogen deficiency and testosterone deficiency. High prolactin levels also can cause unwanted lactation. This often occurs during pregnancy or when the thyroid is not functioning properly. Pituitary tumors, known as prolactinomas, and medications that reduce dopamine can also lead to increased prolactin levels. High levels of prolactin are linked to sexual problems. Some of these conditions can be treated with medications that mimic the action of dopamine.

It’s also possible to have too little prolactin, a condition known as hypoprolactinaemia. This is extremely rare, but it can occur if people have under-active pituitary glands. This is commonly noticed in women after pregnancy who are not able to produce sufficient milk. No other proven health effects of low prolactin levels have been noted. Research is underway to determine if those with low prolactin levels suffer from a reduction in immune system responses.

Prolactin is an important, yet not often well-known, hormone. Take control of your health by understanding your hormones and how they affect you. If you are concerned about prolactin levels or functions, consider asking your healthcare provider:

  • Is prolactin affecting my ability to produce milk?

  • How can I raise or lower my prolactin levels?

  • What concerns are there surrounding prolactin?

  • How can I monitor prolactin levels?

Return to Hormones and Endocrine Function>>>

Function, location, hormones, and more

The thymus is located in the chest behind the breastbone. It plays a key role in immunity by producing white blood cells known as T cells. It also contributes to the production of hormones such as insulin.

The organ’s primary function is maturing T cells, or T lymphocytes. These are white blood cells responsible for fighting infections.

Additionally, the thymus produces an array of hormones. Some of these, like thymulin and thymosin, regulate immune cell production. The thymus also synthesizes hormones such as insulin and melatonin.

It is relatively large in infants and children. After puberty, it decreases in size, and is very small in older adults.

Read on to learn about the thymus’s function, location, and more.

The thymus is an essential part of the immune system. Without it, the immune system cannot function properly.

Early studies in the 1960s tested its importance by removing it from mice. The experiments showed mice without a thymus had immunodeficiency, which is a failure of the immune system to fight infection.

The thymus is responsible for producing and maturing lymphocytes, or immune cells. These include T cells, a type of white blood cell that defends the body from infections.

Additionally, the thymus suppresses the effects of aging, according to a 2016 study.

Hormones released by the thymus inhibit the aging processes. They also help retain learning and memory capabilities.

The thymus is located in the upper chest, behind the breastbone.

It is in front of the ascending aorta, a large blood vessel coming from the heart.

Click on the BodyMap above to interact with a 3D model of the thymus.

The thymus is a soft gland with two lobes. Each lobe has a central par, known as the medulla, and an outer part, known as the cortex.

It is large in infants and young children, but it decreases in size after puberty. By the time a person reaches early adulthood, fat has largely replaced the tissues in the thymus.

The size of the thymus is very small in older adults.

The thymus produces several hormones. Most notably, it produces thymosin, which stimulates T cell production.

Researchers think thymosin acts upon the T cells that have matured in the thymus and prepares them for use throughout the body.

When T cells mature within the thymus, they are not capable of fighting viruses, bacteria, and foreign antigens. After the T cells leave the thymus, thymosin ensures they undergo complete maturation. This makes them capable of performing their duties as part of the immune system and protecting the body from harm.

Additionally, research indicates that thymosin and other thymic hormones inhibit aging.

Some of these effects involve helping preserve learning and memory capacity as people age.

The thymus also makes hormones that are similar to the hormones other glands in the body produce. They include:

  • Melatonin: a sleep-regulating hormone that comes from the pineal gland
  • Insulin: a blood sugar regulating hormone made by the pancreas
  • Growth hormone: a growth-regulating hormone from the pituitary gland
  • Prolactin: a breast-development hormone from the pituitary gland

The thymus contains various types of cells including epithelial and lymphatic cells. They include:

T cells

The thymus matures T cells which critically support the immune system.

Once fully mature, they help fight:

  • Tumors: Cancerous masses
  • Allergens: Substances that cause allergic reactions
  • Pathogens: Microbes, such as viruses and bacteria, that can cause an infection

B cells

The thymus also has a small population of B lymphocytes, or B cells.

Evidence suggests these B cells develop in the thymus and are different from B cells elsewhere in the body. They are referred to as thymic B cells.

Research shows that thymic B cells aid in negative selection of lymphocytes. This means they detect potentially harmful cells that interact too strongly with antigens, which are toxins.

Although thymic B cells play an important role in maintaining healthy cells, their function is not fully understood. Researchers are further investigating how they work.

Conditions causing dysfunction of the thymus gland can drastically reduce a person’s quality of life.

Here are some of the most common conditions:


Various disorders can enlarge the thymus and cause it to become hyperactive, or overly active.

These may include:

  • tumors of the thymus
  • cancers of the lymphatic system
  • myasthenia gravis, an autoimmune disease involving muscle weakness
  • systemic lupus erythematosus, an autoimmune disease affecting the skin, joints, brain, kidneys, and other organs
  • hyperthyroidism, the increased production of thyroid hormones

Symptoms of a hyperactive thymus include:

  • inflammation of the tonsils
  • runny nose
  • enlargement of the lymph nodes

Small size or atrophy

Usually, the thymus is largest in babies and young children. However, some preterm newborns may have a small thymus. This can increase their risk of infections.

When people age, their thymus atrophies, or decreases in size. This raises their likelihood of developing:

  • cancer
  • viral and bacterial infections
  • autoimmune diseases

Thymus cancer

The thymus may develop two types of cancer: thymoma and thymic carcinoma. They are both rare forms of cancer, and they grow in the cells covering the thymus.

Thymoma is a slow-growing cancer that rarely spreads beyond the thymus.

Thymic carcinoma is a faster-growing cancer that is harder to treat.

Symptoms of these cancers may include:

  • persistent cough
  • shortness of breath
  • hoarse voice
  • chest pain
  • swelling in the neck, face, arms, or upper body

The thymus is an organ in the upper chest. It is largest in infants and young children, and it decreases in size after puberty.

It plays a critical role in immunity. Its primary function involves T cell maturation. These cells help the body fight diseases, cancers, allergens, and more.

The thymus also contains B cells. They help the thymus select the best T cells while disposing of potentially harmful ones.

Conditions affecting the thymus include hyperactivity from enlargement, cancer, and atrophy.

The structure of the thyroid gland

The most important part of the human endocrine system is the thyroid gland, it synthesizes a number of hormones that maintain the body’s homeostasis. Disorders in the endocrine system can manifest themselves with numerous unpleasant symptoms.

By the way, most people are not even aware that the source of many troubles is the thyroid gland – a small organ that is only four centimeters long.

Many do not even know its location and come to doctors with “some kind of swelling” on the neck, in which case the pathology becomes very noticeable and, unfortunately, very neglected.

The thyroid gland is a paired symmetrical organ located in front of the trachea. In shape, the organ resembles a butterfly and consists of an isthmus, left and right parts.

Normally, this organ is in a euthyroid state; it is almost imperceptible and soft on palpation. In an inflamed state, for example, in the case of thyroiditis, the thyroid gland increases in size and can swell to a volume that compresses the airways, which makes it difficult to swallow and breathe.

The size of the thyroid gland can vary depending on the hormonal status and age of the individual. So, for example, at the time of puberty, a slight increase in the organ can be observed, while in old age the thyroid restores its volumes.

In other cases, the observed changes in the mass and size of the thyroid should be the reason for contacting an endocrinologist. Particular attention should be paid to the health of this organ for pregnant women.

The hormones synthesized by the thyroid gland are the peptide hormone calcitonin, as well as the iodine-containing hormones triiodothyronine and thyroxine. In the absence of molecular iodine in the body, there is no synthesis of T3 (triiodothyronine) and T4 (thyroxine).

The thyroid gland must always have a supply of thyroglobulin, a protein that contains tyrosine (an amino acid for the synthesis of iodine-containing hormones). The fact is that the processes of the thyroid gland localized in the apical part of the epithelium can be triggered only in the presence of the enzyme thyroid peroxidase. T3 and T4 are abbreviations for the hormones of the iodine-containing group, the numbers indicate the number of iodine molecules required for the synthesis of each of them.

The body receives the hormone calcitonin from the C-cells of the thyroid gland and the parathyroid glands. This hormone is responsible for calcium metabolism, regeneration and growth of muscle and bone tissue, and muscle performance largely depend on it. Insufficiency of this hormone (for example, with autoimmune thyroiditis or hypothyroidism) leads to impaired absorption of calcium from food and problems with the musculoskeletal system.

Hormones produced by the thyroid gland regulate vital processes in the body and are required by all organs and tissues. These hormones bind to the chromosomes in the cell nucleus, thereby stimulating reduction and oxidative reactions, as well as the process of synthesis of new substances.

If cells are deprived of thyroid hormones, they will not be able to protect themselves from the negative effects of free radicals, and the functioning of the antioxidant system will be impossible. The hormones produced by the thyroid gland maintain the heat balance in the body, maintain the temperature background required for the work of other hormones and enzymes. It is the thyroid hormones that “engage” in the regulation of cell division, growth and differentiation, and also regulate apoptosis (programmed cell death).

Without these hormones, the normal functioning of the immune system, the activity and production of immune T-cells is unthinkable.

Insufficiency of thyroid hormones can lead to impaired growth and puberty in humans, diseases of the bone tissue, as well as pathologies of the brain in the fetus with impaired thyroid function in pregnant women.

Our medical center offers you a thyroid health examination.

An experienced endocrinologist is waiting for you for a consultation. Here you can perform the necessary blood tests for thyroid hormones and thyroid ultrasound.

Pre-registration required.

Hyperthyroidism in dogs: symptoms, treatment

Hyperthyroidism in dogs is a condition of increased secretion of thyroid hormones into the blood. Hyperthyroidism occurs in both animals and humans.

There is currently no consensus among veterinarians on the incidence of hyperthyroidism in dogs. Most likely, this is due not to rare cases, but to their incomplete detection.

In order to understand why hyperthyroidism occurs, let’s turn to the structure and functioning of the thyroid gland in the norm.

The thyroid gland (Fig. 1) in a dog is located on the right and left sides of the trachea, looks like tonsils, which can be connected by an isthmus.

Fig. 1. Location of the thyroid gland in a dog.

Nearby is the esophagus, muscles, and most importantly blood vessels that wrap around the gland, penetrate and branch out in it.

Outside, the thyroid gland in a dog is covered with a shell of connective tissue, from which partitions extend deep into the organ (Fig. 2, No. 1), it is through them that the blood (Fig. 2, No. 2), lymphatic vessels and nerves pass. Septa divide the organ into lobules, inside which are “sacs” or follicles (Fig. 2, No. 3), filled with a complex chemical substance or colloid (Fig. 2, No. 4), which is rich in iodine.

Fig. 2. The internal structure of the thyroid gland of a dog.

The wall of the follicle is built from a single layer of cells (Fig.2, No. 5), the colloid acts on them and stimulates the production of hormones. It is through the blood vessels that all these substances enter the body, therefore the thyroid gland belongs to the organs of internal (endocrine) secretion.

Normally, the thyroid gland of a dog produces thyroid hormones, which include:

  • tetraiodothyronine (thyroxine, T4): it accounts for 3/4 of the total iodine contained in the blood;
  • triiodothyronine or T3: formed 5-10 times less than T4, but it is more active than the latter.

The main functions of these hormones:

  • participation in the formation and development of tissues;
  • stimulation of the cardiovascular system;
  • participation in the conduction of nerve impulses to tissues and organs;
  • participation in general metabolism;
  • improved oxygen absorption by tissues, resulting in the release of excess heat, which means that the body expends more energy on vital processes;
  • influence on the activity of certain enzymes;
  • action on the genetic apparatus of the cell (for example, triiodothyronine).

The production of thyroid hormones directly depends on the work of other endocrine glands, in particular the hypothalamus and pituitary gland. Between these glands there is an inextricable connection.

Causes of hyperthyroidism in dogs

The occurrence of hyperthyroidism in dogs can be congenital or acquired.

Congenital hyperthyroidism in the dog . There are experimental data that suggest that if during pregnancy the mother had, for example, exhaustion, which provoked a metabolic disorder in her body, then this directly affects the high level of thyroid hormones in newborn puppies. However, after birth, tissues begin to grow rapidly, which requires more thyroid hormones. Therefore, the more exhausted the mother was, the more hormones the puppy needs, and by the age of about 4 months their blood level becomes below normal. In this case, another, the most common and dangerous disease of the thyroid gland in dogs occurs – hypothyroidism, that is, an insufficient amount of thyroid hormones.

Also, congenital hyperthyroidism in a dog can develop as a result of an autoimmune disease (translated from Latin, “auto” means “self” or “own”). This is a condition in which the immune system is not able to recognize the tissues of its own body, and in this case, thyroxine. In response, the body synthesizes special proteins – defenders or autoantibodies, which begin to “attack” both the thyroid gland and other organs, which leads to disruption of their work.

Acquired hyperthyroidism in a dog may develop as a result of:

  • excessive administration of thyroid hormones into the body;
  • development of a hormonally active malignant tumor of the thyroid gland (thyroid carcinoma). But this is a rare case, only 25% of all tumor processes in the gland;
  • diseases of the pituitary gland.

An increase in the amount of thyroid hormones is also possible during pregnancy.

It is important to note that hyperthyroidism in dogs does not develop spontaneously; in itself, such a condition is always a consequence of serious disturbances in the hormonal work of the whole organism .

Symptoms of hyperthyroidism in dogs

The maximum frequency of registration of hyperthyroidism in dogs on the following grounds:

  • breed: Keeshond, followed by Labrador Retriever and Doberman. All dogs are prone to developing the disease;
  • age: from seven years and more. There is evidence that in such animals, changes in the thyroid gland occur as early as about 2 years.

The first signs of the disease are:

  • behavioral change: restlessness, agitation or lethargy, in some cases aggression;
  • sudden increase or decrease in weight: the dog may eat a large amount of food, but lose weight rapidly;
  • palpitations;
  • digestive and respiratory disorders;
  • fever;
  • trembling of limbs;
  • thirst;
  • hair loss and thickened nails.

In very difficult cases, the most striking sign of hyperthyroidism in a dog may be the so-called “bulging eyes” or Basedow’s disease. It is described in classic textbooks on veterinary medicine as follows: “… a special kind of “bulging eyes” is recorded in a dog, that is, the eyeball sharply protrudes outward …”, and visually it seems that the animal has huge eyes.

The thyroid gland itself is enlarged on the right and left (in almost 70% of the examined animals). Processes in it can go in two directions. The first is when the iron increases by increasing the amount of the colloid itself. The second is when the gland increases due to the growth of connective tissue (septa). This condition of the gland is called a goiter, fortunately, it develops extremely rarely in dogs.

An atypical (uncharacteristic) form of hyperthyroidism in dogs has also been described:

  • poor appetite;
  • exhaustion and weakness;
  • depression.

As the disease progresses and organ involvement occurs, symptoms may increase. In advanced cases, the animal may die.

Diagnosis of hyperthyroidism in dogs

  1. Questioning the history of the disease and examining the dog.
  2. To understand the state of the body, a general blood and urine test is prescribed.
  3. Blood test for hormones.
  4. Electrocardiography – to monitor the cardiovascular system, ultrasound (Fig. 3) and X-ray – to exclude tumor processes and metastases in the chest cavity.
  5. Other studies based on the general condition of the animal.

Fig. 3. Hyperthyroidism in a Labrador. Ultrasound of the left lobe of the thyroid gland.

In the treatment of hyperthyroidism, it is necessary to control the dog’s condition with repeated examinations, some laboratory tests (general blood count, hormone levels) every 2-3 weeks, at least the first 3 months, then as needed.

Treatment of hyperthyroidism in dogs

Treatment depends on the general condition of the body. If we are talking about severe or advanced cases, then treatment can only try to improve the quality of life of the dog.

As for the work of the thyroid gland itself, the primary task is to normalize the production of hormones using special or antithyroid drugs. Their choice, calculation of the dose and frequency of administration can only be prescribed by a veterinarian based on the results of the examination. The owner should be made aware of the possible side effects of each drug, and if it develops, the drug is canceled and a replacement is selected .

As an alternative method, the specialist may suggest surgical removal of the thyroid gland. It is important to know the consequences: the body needs hormones anyway, which means that it is necessary to maintain their blood level with drugs in the form of injections or tablets for the rest of your life.

If the cause of hyperthyroidism in a dog is a tumor, then the treatment strategy is determined by the oncologist.

At the same time, concomitant diseases (heart, gastrointestinal tract, etc.) are being treated.

Prevention of hyperthyroidism in dogs

Prevention of hyperthyroidism in dogs has not yet been developed.

Prognosis for hyperthyroidism in dogs

In this disease, the prognosis is favorable in case of:

  • if the dog’s hyperthyroidism is not complicated by serious diseases of other organs or a tumor process;
  • if the owner strictly follows all the recommendations of the veterinarian.