Endo 101


Often referred to as the body’s “master” gland because it secretes hormones that regulate the function of other endocrine glands (the thyroid, adrenals and reproductive glands), the pituitary also produces hormones that stimulate the growth of bones and tissues, affect sexual development, encourage water reabsorption by the kidneys and trig­ger uterine contractions during and after labor.

Pineal Gland

Located deep in the center of the brain, the pineal gland is involved in several body functions, including secretion of the hormone mela­tonin, which helps maintain a person’s wake/sleep cycles and regulate reproductive hormones and the conversion of nervous system signals to endocrine signals.


The hypothalamus, located just above the brain stem, serves as the link between the endocrine system and the nervous system via the pituitary gland by controlling the pituitary through the stimulation or suppression of hormone secre­tions. It activates and controls invol­untary functions such as body temperature, hunger, thirst and fatigue.

Parathyroid glands

The body’s four parathyroid glands monitor the calcium level in the blood. As blood filters through the para­thyroids, they detect the amount of calcium and make more parathyroid hormone (PTH) when calcium levels are too low. Once the PTH is released, it circulates to the cells of the bones and causes them to release calcium into the bloodstream. When calcium levels are too high, the parathyroids make less PTH or cease producing it until normal levels are restored. Calcium is the element that allows the normal conduction of electrical currents along nerves—it’s how our nervous system works, how one nerve ‘talks’ to the next, and is the primary element which causes muscles to contract. The para­thyroids also help the lining of the intestines become more efficient at absorbing calcium in the diet.

Thyroid gland

The butterfly-shaped thyroid takes iodine and converts it into two hormones (T3 and T4), which are transported throughout the body and enter cells to regulate blood pressure, body temperature, heart rate, metabolism and how the body reacts to other hormones. The thyroid gland also produces calcitonin, which stimulates bone cells to add calcium to bone, as well as regulating calcium metabolism.

Adrenal glands

Located atop the kidneys, adrenal glands are responsible for the secretion of more than 35 different hormones which maintain the body’s salt and water balance, affect kidney function and help the body cope with and respond to stress. During stressful situations, the adrenals release adrenaline and the gland’s cortex releases cortisol to convert proteins into energy, leading to the release of the body’s stored sugar (glycogen). Glycogen generates energy that accelerates our heart, respiratory rate and blood pressure, thus providing the body the fuel required for a quick response in a crisis. The adrenal glands also produce androgens, male sex hormones that promote the development of male characteristics, and estrogen, which is an essential hormone for female body metabolism.


The pancreas is both a digestive organ and an endocrine gland. The “islets of Langerhans” are the regions of the pancreas that contain its hormone-producing cells. The two primary endocrine functions of these cells are to keep the body supplied with fuel for energy by maintaining a steady level of glucose (sugar) in the bloodstream with the hormones insulin and glucagon and to help in food digestion by secreting digestive enzymes.


The testes, also known as testicles or male gonads, have two functions: to produce sperm and to produce hormones, particularly testosterone, which regulate body changes associated with sexual develop­ment, including enlargement of the penis, the growth spurt that occurs during puberty, and the appearance of other male secondary sex characteristics such as deepening of the voice, growth of facial and pubic hair, and the increase in muscle growth and strength.


The ovaries, the female gonads, have two main reproductive func­tions: they produce oocytes (eggs) for fertilization and the reproductive hormones estrogen and proges­terone. Estrogen is responsible for the development of female sexual features such as breast growth, the accumulation of body fat around the hips and thighs, and the growth spurt that occurs during puberty. Both estrogen and progesterone are also involved in the regulation of the menstrual cycle and prepare the lining of the uterus for pregnancy.


Click on a letter to learn Endocrinology terms



The abdomen is the region of the body that contains all of the structures between the chest and the pelvis such as the stomach, small intestine, colon, rectum, liver, spleen, pancreas, kidneys, appendix, bladder and gallbladder.

Abdominopelvic cavity

The body cavity that includes the stomach and pelvic cavity. This cavity is lined with a membrane that creates two spaces called the peritoneal and the retroperitoneal space that contains the pancreas, the adrenal glands, and kidneys.

Adrenal cortex

The adrenal cortex is the outside part of the adrenal gland that produces steroid hormones which control carbohydrates, fat metabolism and mineralocorticoid hormones. Mineralocorticoid hormones regulate salt and water balance in the body.

Adrenal glands

The adrenal glands, located on the top of each kidney, are glands that produce hormones which help control the way the body uses food, the levels of minerals such as sodium and potassium in the blood, heart rate, blood pressure, and other functions particularly involved in stress reactions. These hormones are very important to a person’s health and well-being.

Adrenal medulla

The adrenal medulla is the inner part of the adrenal gland that produces adrenaline, specifically, epinephrine (adrenaline), norepinephrine (noradrenaline).


Adrenaline includes two specific hormones, epinephrine and norepinephrine, which when secreted affects the caliber, or size, of blood vessels throughout the body. This includes the heart, brain, skin, muscles and all organs. When released, these hormones cause a rapid pulse, higher blood pressure, shakiness, sweating, pallor or blanching of the skin. Adrenaline is produced under stressful or exciting situations.


The study of the human body by observation or examination.

Anterior Pituitary

Anterior Pituitary is the front of the pituitary gland that produces and secretes the following important endocrine hormones such as the growth hormone, thyroid-stimulating hormone (TSH), adrenocorticotropic hormone (ACTH), prolactin, luteinizing hormones.


A blood vessel that moves blood away from the heart.

Autonomic nervous system

The autonomic nervous system is the part of the nervous system that controls your heart beat and digestion. The autonomic nervous system affects many organ systems. Blood pressure problems, heart problems, trouble with breathing and swallowing, and erectile dysfunction in men may occur when the autonomic nervous system is not functioning properly.


Blood pressure

Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps blood.


The brain is the center of the human nervous system located within the skull and functions as a primary receiver, organizer, and distributor of information for the body. It controls your walking, talking, swallowing, breathing, taste, smell, etc.



C-peptide is a result of insulin, made by the pancreas. The level of C-peptide is a tester of how much insulin is being produced in the body.


Calcium is an essential endocrine mineral and is a vital source for bone strength and inflammation. Almost all of the body’s calcium is store in the bones and teeth.

Central nervous system

The central nervous system (CNS) consists of the brain, including the cranial nerves and the spinal cord. The brain and spinal cord serve as the main processing center for the entire nervous system and controls all the workings of your body.

Circadian rhythms

Circadian rhythms are physical, mental and behavioral changes that follow a roughly 24-hour cycle, responding primarily to light and darkness of an individual’s day.

Circulatory System

The circulatory system is a make-up of your heart and blood vessels providing a continuous supply of water, nutrients and blood flowing through the body.


The cortex is the outer layer of any organ.


Cortisol is a stress hormone produced by the adrenal cortex.



A physician that treats people who have diabetes.

Diabetes Mellitus

Diabetes Mellitus or diabetes is an endocrine disease in which your blood glucose, or sugar is too high. This results from the body’s inability to use sugar for energy. In type 1 diabetes, the pancreas no longer produces insulin. In type 2 diabetes, either the pancreas does not make enough insulin or the body is unable to use insulin properly.

Diabetic Neuropathy

Diabetic Neuropathy is nerve damage as a result of diabetes and may lead to loss of feelings in hands, arms, toes and feet.

Diabetic Retinopathy

Diabetic retinopathy is caused by diabetes that can eventually lead to blindness due to the damaging of small blood vessels that are located in the retina.


Diagnosis is the determination of a disease from its sign and symptoms.

DPP-4 Inhibitor

DPP-4 inhibitor is a class of oral medicine used to treat type 2 diabetes that lowers blood glucose by helping the body make more insulin when it’s needed.


Endocrine system

The endocrine system consists of the glands that discharge different types of hormones directly into the bloodstream regulating the body’s functions such as metabolism, mood, tissue function, growth and development.


Endocrinology is a specialty that examines the glands and hormones of the body.


A physician who specializes in endocrinology.


Enzymes are proteins that cause specific chemical reactions that are important body functions.


Estrogen is a hormone that is produced by the ovaries and changes naturally over the female lifespan reaching adult levels with the onset of puberty and then decreasing in middle age until the onset of menopause. Estrogen is also produced in smaller amounts by the adrenal cortex, placenta and male testes.


Exocrine are hormones or enzymes that are secreted directly into a vessel and, from the duct, they flow either into the bloodstream or from cell to cell.


Follicle-Stimulating Hormone

A hormone released from the anterior pituitary. In females, Follicle-Stimulating Hormone (FSH) stimulates the maturation of ovarian follicles. In males, Follicle-Stimulating Hormone (FSH) is critical for sperm production and supports sperm cell maturation.



Gamete is a cell that combines with another cell during conception.


The gland is an organ that releases substances like hormones into the bloodstream, endocrine gland or, through ducts, exocrine gland.


Glucocorticoid is a hormone that mainly affects the metabolism of carbohydrates.


Glucose is the main source of energy or fuel for all of the body’s functions. Although the body gets most of its glucose from carbohydrates in food, glucose can also be made from protein and fat.


Gonads are the main reproductive organs the testes in males and ovaries in females.


Gonadotropins are hormones that stimulate the ovaries and testicles.

Graves’ Disease

Graves’ disease is an autoimmune disease relating to the thyroid. This disease occurs when the thyroid is overactive and produces an extreme amount of thyroid hormones.

Growth hormone

Growth hormone is a hormone produced by the pituitary gland, located in the brain, that fuels childhood growth and helps maintain tissues and organs throughout life.


Gynecomastia is the enlargement of breast tissue in males. Breast enlargement is common in men and boys at various stages of development, but also may be associated with certain medical conditions. When fat tissue is present in the breast, it is called pseudogynecomastia.


Hashimoto’s thyroiditis

Hashimoto’s Thyroiditis is an autoimmune disease and is the most common thyroid disease in the United States. Hashimoto’s Thyroiditis occurs when there is inflammation of the thyroid. It is characterized by the production of immune cells and autoantibodies of the body’s immune system, which can damage thyroid cells and interfere with their ability to make thyroid hormones.


The heart is the muscle that pumps blood throughout the blood vessels. The heart is comprised of four chambers and is located in the chest behind the breastbone.

Heart rate

The heart rate is the number of times the heart beats in a minute.


Hirsutism is a condition of unwanted male-pattern hair growth in women resulting in excessive amounts of coarse and pigmented hair on body areas where men typically grow hair, like the face, chest, abdomen and back.


A hormone is a chemical messenger released by a cell that transports a signal from one part of the body to other cells of the body.


Hyperglycemia is an elevation of glucose (blood sugar) that is above normal levels.


Hyperthyroid is a condition when you have an overactive thyroid gland producing excessive amounts of thyroid hormone. When this occurs, the body's metabolism is increased and can cause a variety of symptoms. (See Grave’s Disease).


Hypoglycemia is low blood sugar.


Hypothalamus is a component of the brain that connects the nervous system to the endocrine system through the pituitary gland. This component controls the molecules that make you feel exhilarated, angry or unhappy, wakes you up in the morning, activates adrenaline during stress, controls body temperature, hunger, thirst, fatigue, sleep, and circadian cycles.


Hypothyroid is a condition when you have an underactive thyroid which doesn't produce enough of certain important hormones.



Immune is the presence of antibodies or lymphocytes that protect your body from infections and diseases.

Immune system

The immune system is a complex network of interacting cells (lymphocytes), cell products and cell-forming tissues that protect the body from pathogens and other foreign substances. The immune system also destroys infected and malignant cells, and removes cellular debris.


Insulin is a natural hormone made by the pancreas that controls the level of sugar glucose in the blood.




The kidney, located on each side of the body, is what receives and filters waste products, minerals and water from the blood. Water from the blood undergoes a series of steps that involve the regulation of sodium, potassium, calcium and acid in order to maintain a stable balance. The kidneys are important for filtering medications and also make substances that help control blood pressure and regulate the formation of red blood cells.



The lobe is part of an organ that appears to be separate in some way from the rest of the organ.

Luteinizing hormone

Luteinizing hormone is the hormone that stimulates ovulation and is involved in the production of estrogen and some androgens. This hormone also stimulates the production of testosterone by the interstitial cells of the testes in the male.

Luteinizing hormone-releasing hormone

Luteinizing hormone-releasing hormone (LHRH), also known as Gonadotropin-releasing hormone (GnRH), helps to control the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is synthesized and released from the hypothalamus.



The medulla is the inner core of certain organs or body structures.


Melatonin is a hormone secreted by the pineal gland that helps control your sleep and wake cycles.


Menarche is the time in a young girl’s life when menstruation first begins. During this time, menstruation may be irregular and unpredictable.


Menopause is a time in a woman’s life when menstrual periods permanently stop.


Menstruation is the periodic blood that flows as a discharge from the uterus.


Metabolism is all of the chemical and physical processes in the body necessary for life. Processes include breaking down food for energy and producing needed substances.


Muscle is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body skeletal, which is responsible for moving extremities and external areas of the body; cardiac, which is the muscle found in the heart; and smooth muscle, which is found in the walls of arteries, lungs and intestines.



The neck is part of the body joining the head to the shoulders. The thyroid is located in the neck.

Neuroendocrine integration

Neuroendocrine integration is a process that unites and coordinates the brain with the endocrine system.



The organ is a relatively independent part of the body that carries out one or more special functions. Examples of organs include the eyes, ears, heart, lungs, and liver.


Osteoporosis is a disease that leads to an increased risk of fracture due to a loss of structure within the bone and an abnormal or poor quality of the bone.


Oxytocin is a hormone that causes the uterus to contract during labor, facilitating birth, and after birth stimulates the nipples facilitating breastfeeding.



The pancreas is a gland near the stomach that helps breakdown food and secretes hormones that help control blood sugar levels.

Parathyroid glands

The parathyroid glands are four glands located behind the thyroid which regulate calcium levels. The parathyroid gland secretes a hormone called parathormone (parathyroid hormone) that regulates calcium and phosphorus metabolism.

Parathyroid hormone

The parathyroid hormone is made by the parathyroid glands and is responsible for maintaining calcium and phosphorus balance by acting on bone and the kidneys.


Pediatric is pertaining to children.

Pineal gland

Pineal gland (also called the pineal body) is a small endocrine gland that produces melatonin, a hormone that affects the modulation of wake and sleep patterns and seasonal functions. Its shape resembles a tiny pine cone (hence its name), and is located near the center of the brain, between the two hemispheres.


The pituitary gland is an endocrine gland that secretes nine hormones regulating metabolism. This gland has two components, the anterior and posterior pituitary.

Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a common hormonal disorder among women of reproductive age. The name of the condition comes from the appearance of the ovaries in most, but not all, women with the disorder. Ovaries are enlarged and contain numerous small cysts located along the outer edge of each ovary (polycystic appearance).

Posterior pituitary

The posterior pituitary which is one of the two lobes of the pituitary gland stores and secretes oxytocin and vasopressin directly into the circulation.


Prediabetes is a condition in which blood sugar levels are higher than normal but not elevated enough to qualify for the diagnosis of diabetes.


Progesterone is a female hormone that prepares the uterus to receive and sustain fertilized eggs.


Prolactin is a hormone secreted by the pituitary gland that stimulates lactation which is milk production. It also has many other functions, including essential roles in the maintenance of the immune system. Abnormally high prolactin can delay puberty, interfere with ovulation in women, decrease libido in men and decrease fertility. Elevated prolactin (hyperprolactinemia) may be due to a benign tumor in the pituitary gland called a prolactinoma.

Pubic Symphysis

The pubic symphysis or symphysis pubis is a joint, composed of cartilage that unites the left and right pubic bones of the pelvis.



Renin-Angiotensin System

Renin-angiotensin system is a hormone system that regulates blood pressure and fluid balance secreted by the kidneys.

Retroperitoneal space

The retroperitoneal space is located in front of the lower back, behind the abdominal lining and includes the pancreas, spleen and kidneys.



The scrotum is a pouch that contains the testes and parts of the spermatic cords.


Somatostatin is a hormone that is widely distributed throughout the body, especially in the hypothalamus and pancreas. It acts as an important regulator of endocrine and nervous system function by inhibiting the secretion of several other hormones such as growth hormone, insulin, and gastrin.


The male gamete or sex cell.


A steroid is one of the large group of chemical substances classified by a specific carbon structure. Steroids include drugs used to relieve swelling and inflammation, such as prednisone and cortisone; vitamin D; and some sex hormones, such as testosterone and estradiol.


The stomach is a digestive organ that is located in the upper abdomen, under the ribs. The upper part of the stomach connects to the esophagus, and the lower part leads into the small intestine.


Stress is a physical, mental or emotional factor that causes bodily or mental tension.



The testes are a male sex gland located behind the penis in a pouch of skin called the scrotum. The testes produce and store sperm.


Testosterone is a male sex hormone that is produced by the testes and is responsible for male growth and development.


The thalamus is part of the brain that relays sensory and motor signals to the cerebral cortex and regulates consciousness, sleep, and alertness.


Thermostat is a device that monitors temperature and automatically maintains it at certain levels. In humans, the tiny part of the brain called the hypothalamus which is located behind the eyes serves as the thermostat. It can warm the body by causing it to shiver and cool the body by causing it to perspire. The hypothalamus also regulates hunger, thirst, sex drive and other body activities.


The thyroid is a butterfly-shaped gland in the middle of the neck that produces two hormones, triiodothyronine (T3) and thyroxine (T4).

Thyroid hormones

Produced by the thyroid gland, under stimulation by the pituitary (TSH), T3 (triiodothyronine) and T4 (tyrosine). A deficiency of iodine leads to decreased production of T3 and T4, enlarges the thyroid tissue and will cause the disease known as goiter. The major form of thyroid hormone in the blood is thyroxine (T4).


Thyroiditis is inflammation of the thyroid gland (see hyperthyroid).


Thyroid-stimulating hormone (TSH) is a thyroid stimulating hormone. TSH levels in your bloodstream rise or fall depending on whether enough thyroid hormone is produced to meet your body’s needs. Higher levels of TSH prompt the thyroid to produce more thyroid hormone. Conversely, low TSH levels signal the thyroid to slow down production.



The uterus is a hollow, pear-shaped organ that is located in a woman's lower abdomen, between the bladder and the rectum that stores the fertilized egg until the unborn child is ready to be born.



Vasopressin is a hormone produced by the posterior pituitary. Vasopressin has an antidiuretic action, hence causing water retention and preventing the production of dilute urine.