Complete Endocrine System: Glands, Hormones and Disorders

Disorders of the Adrenal Glands

Addison's disease: This rare disorder may affect anyone at any age. It develops when the adrenal cortex fails to produce enough cortisol and aldosterone. To learn more, read our article about Addison's Disease. Adrenal cancer: Adrenal cancer is an aggressive cancer, but it's very rare. Malignant adrenal tumors are rarely confined to the adrenal glands—they tend to spread to other organs and cause adverse changes within the body because of the excess hormones they produce. To learn more, read our article about adrenal cancer. Cushing's syndrome: Cushing's syndrome is an uncommon condition that is essentially the opposite of Addison's disease. It is caused by overproduction of the hormone cortisol. There are a variety of causes of this disorder—a tumor in the adrenal gland or pituitary gland could be to blame. To learn more, read our article about Cushing's syndrome. Congenital adrenal hyperplasia: This genetic disorder is characterized by low levels of cortisol. It's common for people with congenital adrenal hyperplasia to have additional hormone problems such as low levels of aldosterone (which maintains a balance of water and salt).

Adrenal Gland Hormones

Adrenal Cortex Hormones The adrenal cortex produces two main groups of corticosteroid hormones—glucocorticoids and mineralcorticoids. The release of glucocorticoids is triggered by the hypothalamus and pituitary gland. Mineralcorticoids are mediated by signals triggered by the kidney. When the hypothalamus produces corticotrophin-releasing hormone (CRH), it stimulates the pituitary gland to release adrenal corticotrophic hormone (ACTH). These hormones, in turn, alert the adrenal glands to produce corticosteroid hormones. Glucocorticoids released by the adrenal cortex include: Hydrocortisone: Commonly known as cortisol, it regulates how the body converts fats, proteins, and carbohydrates to energy. It also helps regulate blood pressure and cardiovascular function. Corticosterone: This hormone works with hydrocortisone to regulate immune response and suppress inflammatory reactions. The principle mineralcorticoid is aldosterone, which maintains the right balance of salt and water while helping control blood pressure. There is a third class of hormone released by the adrenal cortex, known as sex steroids or sex hormones. The adrenal cortex releases small amounts of male and female sex hormones. However, their impact is usually overshadowed by the greater amounts of hormones (such as estrogen and testosterone) released by the ovaries or testes. Adrenal Medulla Hormones Unlike the adrenal cortex, the adrenal medulla does not perform any vital functions. That is, you don't need it to live. But that hardly means the adrenal medulla is useless. The hormones of the adrenal medulla are released after the sympathetic nervous system is stimulated, which occurs when you're stressed. As such, the adrenal medulla helps you deal with physical and emotional stress. You can learn more by reading a SpineUniverse article about the sympathetic nervous system. You may be familiar with the fight-or-flight response—a process initiated by the sympathetic nervous system when your body encounters a threatening (stressful) situation. The hormones of the adrenal medulla contribute to this response. Hormones secreted by the adrenal medulla are: Epinephrine: Most people know epinephrine by its other name—adrenaline. This hormone rapidly responds to stress by increasing your heart rate and rushing blood to the muscles and brain. It also spikes your blood sugar level by helping convert glycogen to glucose in the liver. (Glycogen is the liver's storage form of glucose.) Norepinephrine: Also known as noradrenaline, this hormone works with epinephrine in responding to stress. However, it can cause vasoconstriction (the narrowing of blood vessels). This results in high blood pressure.

Pituitary Gland Hormones

Anterior Lobe Hormones: Adrenocorticotropic hormone (ACTH): ACTH stimulates the adrenal glands to produce hormones. Follicle-stimulating hormone (FSH): FSH works with LH to ensure normal functioning of the ovaries and testes. Growth hormone (GH): GH is essential in early years to maintaining a healthy body composition and for growth in children. In adults, it aids healthy bone and muscle mass and affects fat distribution. Luteinizing hormone (LH): LH works with FSH to ensure normal functioning of the ovaries and testes. Prolactin: Prolactin stimulates breast milk production. Thyroid-stimulating hormone (TSH): TSH stimulates the thyroid gland to produce hormones. The posterior lobe contains the ends of nerve cells coming from the hypothalamus. The hypothalamus sends hormones directly to the posterior lobe via these nerves, and then the pituitary gland releases them. Posterior Lobe Hormones: Anti-diuretic hormone (ADH): This hormone prompts the kidneys to increase water absorption in the blood. Oxytocin: Oxytocin is involved in a variety of processes, such as contracting the uterus during childbirth and stimulating breast milk production.

Hypothalamus Hormones

Anti-diuretic hormone (ADH): This hormone increases water absorption into the blood by the kidneys. Corticotropin-releasing hormone (CRH): CRH sends a message to the anterior pituitary gland to stimulate the adrenal glands to release corticosteroids, which help regulate metabolism and immune response. Gonadotropin-releasing hormone (GnRH): GnRH stimulates the anterior pituitary to release follicle stimulating hormone (FSH) and luteinizing hormone (LH), which work together to ensure normal functioning of the ovaries and testes. Growth hormone-releasing hormone (GHRH) or growth hormone-inhibiting hormone (GHIH) (also known as somatostain): GHRH prompts the anterior pituitary to release growth hormone (GH); GHIH has the opposite effect. In children, GH is essential to maintaining a healthy body composition. In adults, it aids healthy bone and muscle mass and affects fat distribution. Oxytocin: Oxytocin is involved in a variety of processes, such as orgasm, the ability to trust, body temperature, sleep cycles, and the release of breast milk. Prolactin-releasing hormone (PRH) or prolactin-inhibiting hormone (PIH) (also known as dopamine): PRH prompts the anterior pituitary to stimulate breast milk production through the production of prolactin. Conversely, PIH inhibits prolactin, and thereby, milk production. Thyrotropin releasing hormone (TRH): TRH triggers the release of thyroid stimulating hormone (TSH), which stimulates release of thyroid hormones, which regulate metabolism, energy, and growth and development.

Disorders of the Pituitary Gland

Diseases and Disorders of the Pituitary Gland Pituitary tumors are the most common pituitary disorder, and many adults have them. However, they are not, in the great majority of cases, life threatening. But that doesn't mean they're harmless—pituitary tumors can disrupt the gland's normal ability to release hormones. There are two types of pituitary tumors—secretory and non-secretory. Secretory tumors secrete too much of a hormone, and non-secretory tumors don't secrete excess hormone. These hormonal imbalances can cause problems in many different areas of the body. If you have a secretory tumor that is overproducing thyroid-stimulating hormone, for instance, you will experience hyperthyroidism. Another pituitary disorder is known as pituitary apoplexy. In some cases, pituitary function can be suddenly disrupted (due to bleeding or trauma), creating a life-threatening shortage of vital hormones. If you think you may have a problem with your pituitary gland, you should talk to an endocrinologist. He or she will help diagnose and treat your hormone-related condition.

Disorders of Thyroid Gland

Diseases and Disorders of the Thyroid There are many diseases and disorders associated with the thyroid. They can develop at any age and can result from a variety of causes—injury, disease, or dietary deficiency, for instance. But in most cases, they can be traced to the following problems: Too much or too little thyroid hormone (hyperthyroidism and hypothyroidism, respectively). Abnormal thyroid growth Nodules or lumps within the thyroid Thyroid cancer Below are some of the most common thyroid disorders. To learn more, read our article about common thyroid problems. Goiters: A goiter is a bulge in the neck. A toxic goiter is associated with hyperthyroidism, and a non-toxic goiter, also known as a simple or endemic goiter, is caused by iodine deficiency. Hyperthyroidism: Hyperthyroidism is caused by too much thyroid hormone. People with hyperthyroidism are often sensitive to heat, hyperactive, and eat excessively. Goiter is sometimes a side effect of hyperthyroidism. This is due to an over-stimulated thyroid and inflamed tissues, respectively. Hypothyroidism: Hypothyroidism is a common condition characterized by too little thyroid hormone. In infants, the condition is known as cretinism. Cretinism has very serious side effects, including abnormal bone formation and mental retardation. If you have hypothyroidism as an adult, you may experience sensitivity to cold, little appetite, and an overall sluggishness. Hypothyroidism often goes unnoticed, sometimes for years, before being diagnosed. Solitary thyroid nodules: Solitary nodules, or lumps, in the thyroid are actually quite common—in fact, it's estimated that more than half the population will have a nodule in their thyroid. The great majority of nodules are benign. Usually a fine needle aspiration biopsy (FNA) will determine if the nodule is cancerous. Thyroid cancer: Thyroid cancer is fairly common, though the long-term survival rates are excellent. Occasionally, symptoms such as hoarseness, neck pain, and enlarged lymph nodes occur in people with thyroid cancer. Thyroid cancer can affect anyone at any age, though women and people over thirty are most likely to develop the condition. Thyroiditis: Thyroiditis is an inflammation of the thyroid that may be associated with abnormal thyroid function (particularly hyperthyroidism). Inflammation can cause the thyroid's cells to die, making the thyroid unable to produce enough hormones to maintain the body's normal metabolism. There are five types of thyroiditis, and the treatment is specific to each.

Disorders of the Testes

Disorders of the Testes: Hypogonadism Hypogonadism is a testicular disorder associated with low testosterone. Having testosterone levels that are too low causes a variety of problems, including: Decreased sex drive Diminished muscle mass Low sperm count (reduced fertility) Loss of body hair There are two types of hypogonadism—primary and secondary. Primary refers to a defect with the testicles, and secondary involves a problem in the pituitary gland that indirectly affects testosterone production. The condition may be caused by many things and is most commonly the result of: Aging Defects in the pituitary and/or hypothalamus, such as pituitary tumors (which adversely affect the pituitary's ability to function normally) and high prolactin levels (too much of the hormone causes a drop in testosterone levels) Medications Testes-based conditions, such as severe injury, and radiation or chemotherapy, can all deplete testosterone levels

Pancreas Hormones

Gastrin: This hormone aids digestion by stimulating certain cells in the stomach to produce acid. Glucagon: Glucagon helps insulin maintain normal blood glucose by working in the opposite way of insulin. It stimulates your cells to release glucose, and this raises your blood glucose levels. Insulin: This hormone regulates blood glucose by allowing many of your body's cells to absorb and use glucose. In turn, this drops blood glucose levels. Somatostatin: When levels of other pancreatic hormones, such as insulin and glucagon, get too high, somatostatin is secreted to maintain a balance of glucose and/or salt in the blood. Vasoactive intestinal peptide (VIP): This hormone helps control water secretion and absorption from the intestines by stimulating the intestinal cells to release water and salts into the intestines.

Hypothalamus

Heart rate and blood pressure Body temperature Fluid and electrolyte balance, including thirst Appetite and body weight Glandular secretions of the stomach and intestines Production of substances that influence the pituitary gland to release hormones Sleep cycles

Ovarie Hormones

Hormones of the Ovaries Ovaries produce and release two groups of sex hormones—progesterone and estrogen. There are actually three major estrogens, known as estradiol, estrone, and estriol. These substances work together to promote the healthy development of female sex characteristics during puberty and to ensure fertility. Estrogen (estradiol, specifically) is instrumental in breast development, fat distribution in the hips, legs, and breasts, and the development of reproductive organs. To a lesser extent, the ovaries release the hormone relaxin prior to giving birth. Another minor hormone is inhibin, which is important for signaling to the pituitary to inhibit follicle-stimulating hormone secretion. Progesterone and Estrogen Production and Function Progesterone and estrogen are necessary to prepare the uterus for menstruation, and their release is triggered by the hypothalamus. Once you reach puberty, the ovaries release a single egg each month (the ovaries typically alternate releasing an egg)—this is called ovulation. The hypothalamus sends a signal to the pituitary gland to release gonadotrophic substances (follicle stimulating hormone and luteinizing hormone). These hormones are essential to normal reproductive function—including regulation of the menstrual cycle. As the egg migrates down the fallopian tube, progesterone is released. It is secreted by a temporary gland formed within the ovary after ovulation called the corpus luteum. Progesterone prepares the body for pregnancy by causing the uterine lining to thicken. If a woman is not pregnant, the corpus luteum disappears. If a woman is pregnant, the pregnancy will trigger high levels of estrogen and progesterone, which prevent further eggs from maturing. Progesterone is secreted to prevent uterine contractions that may disturb the growing embryo. The hormone also prepares the breasts for lactation. Increased estrogen levels near the end of pregnancy alert the pituitary gland to release oxytocin, which causes uterine contractions. Before delivery, the ovaries release relaxin, which as the name suggests, loosens the pelvic ligaments in preparation for labor. More hormones are released during pregnancy than at any other time of a woman's life, but during menopause—which marks the end of fertility—estrogen levels fall fast. This can lead to a range of complications.

Disorders of Parathyroid Gland

Hyperparathyroidism: The most common disease of parathyroid glands is hyperparathyroidism, which is characterized by excess PTH hormone, regardless of calcium levels. In other words, the parathyroid glands continue to make large amounts of PTH even when the calcium level is normal, and they should not be making the hormone at all. Hypoparathyroidism: Hypoparathyroidism is the combination of symptoms due to inadequate parathyroid hormone production. This leads to decreased blood levels of calcium (hypocalcemia) and increased levels of blood phosphorus (hyperphosphatemia).This is a rare condition and most commonly occurs because of damage or removal of parathyroid glands during parathyroid or thyroid surgery. Osteoporosis: When one of the parathyroid glands is overactive, it releases too much PTH hormone. This causes your bones to release calcium constantly into the blood stream. Without enough calcium in your bones, they lose their density and hardness. Osteoporosis is characterized by this loss of calcium and bone density.

Disorders of the Hypothalamus

Hypothalamic Disease A disease or disorder of the hypothalamus is known as a hypothalamic disease. A physical injury to the head that impacts the hypothalamus is one of the most common causes of hypothalamic disease. Hypothalamic diseases can include appetite and sleep disorders, but because the hypothalamus affects so many different parts of the endocrine system, it can be hard to pinpoint whether the root cause of the disorder is actually related to another gland. In particular, the hypothalamus and pituitary gland are so tightly connected that it's often difficult for doctors to determine whether the condition is associated with the hypothalamus or pituitary gland. These are known as hypothalamic-pituitary disorders. However, there are hormone tests that help shed light on which part of the body is the root cause.

Pineal Gland

Melatonin: The Pineal Gland Hormone The pineal gland secretes a single hormone—melatonin (not to be confused with the pigment melanin). This simple hormone is special because its secretion is dictated by light. Researchers have determined that melatonin has two primary functions in humans—to help control your circadian (or biological) rhythm and regulate certain reproductive hormones. Circadian Rhythm Your circadian rhythm is a 24-hour biological cycle characterized by sleep-wake patterns. Daylight and darkness help dictate your circadian rhythm. Light exposure stops the release of melatonin, and in turn, this helps control your circadian rhythms. Melatonin secretion is low during the daylight hours and high during dark periods, which has some influence over your reaction to photoperiod (the length of day versus night). Naturally, photoperiod affects sleep patterns, but melatonin's degree of impact over sleep patterns is disputed. Reproduction Melatonin blocks the secretion of gonadotropins (luteinizing hormone and follicle stimulating hormone) from the anterior pituitary gland. These hormones aid in the proper development and functioning of the ovaries and testes. The pineal gland's full purpose is still a bit of a mystery. But research suggests that we're getting closer to understanding the pineal gland—and more about the endocrine system as a whole.

Disorders of the Ovaries

Osteoporosis: Osteoporosis is commonly associated with menopause, just like mood swings and hot flashes. Menopause is marked by the rapid loss of estrogen. The role estrogen play in bone loss can best be described in terms of a battle between osteoclasts (bone absorbing cells) and osteoblasts (bone producing cells). Estrogen is on the side of the osteoblasts, but as the estrogens diminish, the osteoblasts are discouraged from producing more bone. As such, the osteoclasts win by absorbing more bone than is being produced by the osteoblasts. Estrogen replacement therapy during menopause protects bone mass and helps protect against the risk of osteoporotic fractures. Ovarian Cancer: Ovarian cancer is an extremely serious, but rare, disease. Its symptoms usually don't become apparent until the cancer has progressed into the later stages. Symptoms of ovarian cancer include: persistent abdominal pain, indigestion, bloating, abnormal uterine bleeding, and pain during sexual intercourse. These are common problems, so in the great majority of cases, they will not indicate cancer. However, it's important you pay attention to your body and discuss anything out of the ordinary—no matter how insignificant you think it may be—with your doctor. Ovarian Cysts: Ovarian cysts are fluid-filled sacs that affect women of all ages, though mostly women of child-bearing age. Cysts are very common—and they can range in size from a pea to a grapefruit. The majority of cysts are harmless, though larger cysts (those larger than 5 cm in diameter) may need to be surgically removed because large cysts can twist the ovary and disrupt its blood supply. Cysts can form for a variety of reasons. Oftentimes, they're simply part of normal menstruation. You may experience no symptoms, and the cysts will go away after a few cycles. These are known as functional cysts. The great majority of cysts are benign. But abnormal or pathological cysts, such as those in polycystic ovary syndrome (PCOS), may cause painful symptoms. Treatment for ovarian cysts depends on the size and type of cyst. If you're experiencing pain, talk to your doctor. He or she will determine what treatment is best for you. Below are some common symptoms of pathological cysts: The most telltale symptom is pain and discomfort in the abdomen, vagina, low back, or thighs Breast tenderness Bloating Increased hair growth on your face, back, and chest Pain before or after your menstrual cycle and irregular periods Infertility Weight gain Fatigue Polycystic Ovary Syndrome: Polycystic means "many cysts." Interestingly, the National Institutes of Health (NIH) criteria for diagnosing PCOS do not require the presence of polycystic ovaries by pelvic ultrasound. The NIH criteria are based on signs of hyperandrogenism (or elevated androgens) and oligo/amenorrhea. Other key characteristics include infertility, irregular menstruation, acne, and increased hair growth on the face and body. PCOS is essentially caused by a hormone imbalance—many of the symptoms are caused by increased production of androgens. These patients usually have high free testosterone levels. It's not uncommon for those diagnosed with PCOS to be overweight, insulin resistant, and have type 2 diabetes. Many of the symptoms of PCOS fade with weight loss.

Parathyroid Gland Hormones

PTH regulates how much calcium is absorbed from your diet, how much calcium is excreted by your kidneys, and how much calcium is stored in your bones. We store many pounds of calcium in our bones, and it is readily available to the rest of the body at the request of the parathyroid glands. PTH increases the formation of active vitamin D, and it is active vitamin D that increases intestinal calcium and phosphorus absorption.

Parathyroid Gland

Parathyroid hormone regulates the body's calcium levels. There are four parathyroid glands, and they are each about the size of a grain of rice. Though they're located near each other, the parathyroid glands are not related to the thyroid gland.

Testes Hormones

Testosterone: The Hormone of the Testes Testosterone is necessary for proper physical development in boys. It is the primary androgen, which is the term for any substance that stimulates and/or maintains masculine development. During puberty, testosterone is involved in many of the processes that transition a boy to manhood, including: Healthy development of male sex organs Growth of facial and body hair Lowering of the voice Increase in height Increase in muscle mass Growth of the Adam's apple The importance of testosterone is not limited to puberty. Throughout adulthood, the hormone is integral in a variety of functions, such as: Maintaining libido Sperm production Maintaining muscle strength and mass Promoting healthy bone density Testosterone Production The hypothalamus and pituitary gland control how much testosterone the testes produce and secrete. The hypothalamus sends a signal to the pituitary gland to release gonadotrophic substances (follicle stimulating hormone and luteinizing hormone). Luteinizing hormone (LH) stimulates testosterone production. If too much testosterone is produced, the hypothalamus alerts the pituitary gland to make less LH, which tells the testes to decrease testosterone levels.

Adrenal Gland

The adrenal cortex—the outer part of the gland—produces hormones that are vital to life, such as cortisol (which helps regulate metabolism and helps your body respond to stress) and aldosterone (which helps control blood pressure). The adrenal medulla—the inner part of the gland—produces nonessential (that is, you don't need them to live) hormones, such as adrenaline (which helps your body react to stress).

Pituitary Gland

The hormones of the pituitary gland help regulate the functions of other endocrine glands. The pituitary gland has two parts—the anterior lobe and posterior lobe—that have two very separate functions. The hypothalamus sends signals to the pituitary to release or inhibit pituitary hormone production.

Ovaries

The ovaries maintain the health of the female reproductive system. They secrete two main hormones—estrogen and progesterone. Diseases associated with the ovaries include ovarian cysts, ovarian cancer, menstrual cycle disorders, and polycystic ovarian syndrome.

Pancreas

The pancreas maintains the body's blood glucose (sugar) balance. Primary hormones of the pancreas include insulin and glucagon, and both regulate blood glucose. Diabetes is the most common disorder associated with the pancreas.

Testes

The testes secrete testosterone, which is necessary for proper physical development in boys. In adulthood, testosterone maintains libido, muscle strength, and bone density. Disorders of the testes are caused by too little testosterone production.

Thymus Gland

The thymus gland, located behind your sternum and between your lungs, is only active until puberty. After puberty, the thymus starts to slowly shrink and become replaced by fat. Thymosin is the hormone of the thymus, and it stimulates the development of disease-fighting T cells.

Thyroid Gland

The thyroid regulates your metabolism. The two main thyroid hormones are T3 and T4. Thyroid disorders are common, and they include goiters, hyperthyroidism, and hypothyroidism.

Thymus Gland Hormones

Thymosin stimulates the development of T cells. Throughout your childhood years, white blood cells called lymphocytes pass through the thymus, where they are transformed into T cells. Once T cells have fully matured in the thymus, they migrate to the lymph nodes (groups of immune system cells) throughout the body, where they aid the immune system in fighting disease. However, some lymphocytes, regardless if they reside in the lymph nodes or thymus, can develop into cancers (known as Hodgkin disease and non-Hodgkin lymphomas). Though the thymus gland is only active until puberty, its double-duty function as an endocrine and lymphatic gland plays a significant role in your long-term health.

Disorders of Pancreas

Type 1 diabetes: If you have type 1 diabetes, then your body doesn't produce any insulin to handle the glucose in your body. Insulin deficiency causes a range of complications, so people with type 1 diabetes have to take insulin to help their body use glucose appropriately. To learn more, read our article about type 1 diabetes. Type 2 diabetes: Type 2 diabetes is much more prevalent than type 1. People with type 2 diabetes may be able to produce insulin, but their bodies don't use it correctly. They might also be unable to produce enough insulin to handle the glucose in their body. Lifestyle choices, such as diet and exercise, play a major role in managing and preventing type 2 diabetes. To learn more, read our article about type 2 diabetes. Other common diseases and disorders associated with the pancreas are: Hyperglycemia: This condition is caused by abnormally high blood glucose levels. It can be caused by overproduction of the hormone glucagon. To learn more, read our article about hyperglycemia. Hypoglycemia: Conversely, hypoglycemia is caused by low blood glucose levels. It is caused by a relative overproduction of insulin. To learn more, read our article about hypoglycemia.