Improve your understanding of technical medical and scientific terms with our endocrinology glossary. We provide definitions and understandable explanations of key terms.

AcromegalyAcromegaly is a hormonal disorder where the pituitary gland produces excess amounts of growth hormone.

Adrenal Cortex—The adrenal cortex is the outer portion of the adrenal gland and it produces steroid hormones, which regulate carbohydrate and fat metabolism, and mineralocorticoid hormones, which regulate salt and water balance in the body.

Adrenal GlandsAdrenal glands are triangle-shaped glands that sit on top of the kidneys. They regulate stress response through the synthesis of hormones, including cortisol and adrenaline.

AdrenalineAdrenaline is a hormone that triggers the body’s fight-or-flight response. It is produced in the medulla in the adrenal glands as well as some of the central nervous system’s neurons.

Adrenocorticotropin (ACTH)—Adrenocorticotropin is a hormone produced by the anterior pituitary gland that stimulates the adrenal cortex.

AmenorrheaAmenorrhea is the term used when a woman or adolescent girl is not having menstrual periods.

AndrogensAndrogens are hormones that help to develop sex organs in men. They also contribute to sexual function in men and women.

Andropause—Andropause is a biological change characterized by a gradual decline in androgens experienced by men during and after their mid-life. Andropause is sometimes inaccurately described as male menopause.

AngiotensinAngiotensin is the common name of four hormones: angiotensin I-IV, which play an important role in the body’s overall health and blood pressure regulation.

Antiandrogens—Antiandrogens are substances that inhibit the biological effects of androgenic hormones

Benign Prostatic Hyperplasia (Enlarged Prostate)Benign prostatic hyperplasia is non-cancerous enlargement of the prostate gland, a common occurrence in older men.

Bioavailable Testosterone—Bioavailable testosterone represents the fraction of circulating testosterone that readily enters cells and better reflects the bioactivity of testosterone than does the simple measurement of serum total testosterone.

Bioidentical HormonesBioidentical hormones are compounds that have exactly the same chemical and molecular structure as hormones that are produced in the human body. Though any hormone can be made to be "bioidentical," the term is often used to describe allegedly custom-compounded formulations containing estrogens, progesterone, and androgens. There is no evidence that they are any safer or more effective than FDA-approved hormone preparations.

Bone Mineral Density—A bone mineral density (BMD) test measures the density of minerals (such as calcium) in bones using a special X-ray, computed tomography (CT) scan, or ultrasound. This information is used to estimate the strength of bones.

CalcitoninCalcitonin is a protein hormone secreted by cells in the thyroid gland. It inhibits cells that break down bone and helps to regulate the blood’s calcium and phosphate levels.

CholescystokininCholecystokinin, otherwise known as CCK or CCK-PZ, is able to improve digestion and affects appetite.

Cholesterol—Cholesterol is a white crystalline substance found in animal tissues and various foods that is normally synthesized by the liver. Cholesterol levels can be a risk factor for heart disease.

Congenital Adrenal HyperplasiaCongenital adrenal hyperplasia refers to a group of inherited adrenal gland disorders. People with this condition do not produce enough of the hormones cortisol and aldosterone, and produce too much of androgen.

CortisolCortisol is a hormone produced by the adrenal gland. It is involved in the stress response and increases blood pressure and blood sugar levels.

Cushing SyndromeCushing syndrome is a hormonal disorder caused by prolonged exposure of the body's tissues to high levels of the hormone cortisol. Sometimes called "hypercortisolism," it is relatively rare and most commonly affects adults aged 20 to 50.

DiabetesDiabetes is a disease in which blood glucose levels are above normal. The body of a person with diabetes either doesn't make enough insulin or can't use its own insulin as well as it should.

DehydroepiandrosteroneDehydroepiandrosterone (DHEA) is the highest circulating steroid present in the human body. It is a precursor hormone that can be converted into hormones such as testosterone and estradiol.

Dihydrotestosteronemdash;Dihydrotestosterone is a male hormone more potent than testosterone that is converted from testosterone within the prostate.

Endocrine-disrupting ChemicalsEndocrine-disrupting chemicals (EDCs) are natural and man-made chemicals that can either mimic, block, or disrupt the action of hormones. EDCs are associated with numerous adverse human health issues, including reproductive health problems, obesity, diabetes, hormone-related cancers, neurological issues, and other disorders.

EndocrinologistEndocrinologists are specially trained physicians who diagnose diseases related to the glands. Because these doctors specialize in these conditions, which can be complex and have

hard-to-spot symptoms, an endocrinologist is your best advocate when dealing with hormonal issues.

Erectile Dysfunction (ED)Erectile dysfunction is the inability to achieve penile erection or to maintain an erection until ejaculation.

ErythropoietinErythropoietin is a hormone directly connected to red blood cell production and maintenance. Low levels of this hormone occur when someone has chronic kidney diseases.

EstradiolEstradiol, a type of estrogen, is a female sex hormone produced mainly by the ovaries. It is responsible for growth of breast tissue, maturation of long bones, and development of the secondary sexual characteristics.

EstrogenEstrogens are a group of steroid compounds that are the primary female sex hormones. They promote the development of female secondary sex characteristics and control aspects of regulating the menstrual cycle.

Estrogen Therapy (ET)—Estrogen therapy is a hormone therapy treatment program in which women take estrogen orally, transdermally, or vaginally to treat certain menopausal symptoms

Estrone—Produced by the ovaries, the estrone hormone is one of three types of estrogen. It is a weaker estrogen, commonly found in higher quantities in postmenopausal women.

Free Testosterone—Free testosterone is testosterone in the body that is biologically active and unbound to other molecules in the body, such as sex hormone binding globulin.

Follicle Stimulating Hormone (FSH)—In women, FSH helps control the menstrual cycle and the production of eggs by the ovaries. The amount of FSH varies throughout a woman's menstrual cycle and is highest just before she ovulates. Problems with FSH release can contribute to female infertility. In men, FSH helps control the production of sperm.

GastrinGastrin is a hormone the stomach produces. When you eat, gastrin stimulates the release of gastric acid, an important part of the digestive process.

Ghrelin Ghrelin is central to appetite and the release of growth hormone. Produced in the stomach and small intestine, ghrelin has been called the "hunger hormone" because of its role in controlling appetite.

GlandsGlands produce and secrete hormones that the body uses for a wide range of functions. These control many different bodily functions, including respiration, metabolism, reproduction, sensory perception, movement, sexual development, and growth.

GlucagonGlucagon is a hormone that works with other hormones and bodily functions to control glucose levels in the blood. It comes from alpha cells found in the pancreas and is closely related to insulin-secreting beta cells, making it a crucial component that keeps the body’s blood glucose levels stable.

Glucagon-Like Peptide 1Glucagon-like peptide 1 (GLP-1) helps regulate your appetite, especially after eating. It also helps enhance the production of insulin.

Gonads—A gonad is an organ that produces sperm and egg cells known as gametes. The gonads in males are the testes, and the gonads in females are the ovaries.

Graves DiseaseGraves disease is the most common form of hyperthyroidism. It occurs when your immune system mistakenly attacks your thyroid gland and causes it to overproduce the hormone thyroxine.

Growth HormoneGrowth hormone is a substance that controls your body’s growth. Growth hormone is made by the pituitary gland, located at the base of the brain. Growth hormone helps children grow taller, increases muscle mass, and decreases body fat.

GynecomastiaGynecomastia is breast enlargement in boys or men due to a benign increase in breast tissue. This condition results from an imbalance between the hormones testosterone and estrogen.

HirsutismHirsutism is excessive "male" pattern hair growth that appears on the face, back, chest, abdomen, and thighs in women.

Hormones—Made by endocrine glands, hormones are chemical messengers that travel in the bloodstream to tissues or organs. They affect many processes, including growth, metabolism, sexual function, reproduction, and mood.

Hormone Therapy—Hormone therapy is the use of hormones in medical treatment. For example, doctors may use hormone therapy to boost estrogen levels in menopausal women. Other examples include thyroid hormone replacement for thyroid deficiency, insulin therapy for diabetes, and transgender hormone therapy.

Hot FlashesHot flashes refer to the sudden wave of mild or intense body heat caused by dilation of capillaries in the skin resulting from decreased levels of estrogen. Hot flashes affect about 75 percent of women as they go through menopause.

Human Chorionic Gonadotropin Hormone—The 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.

HypoglycemiaHypoglycemia, also called low blood sugar, occurs when your blood glucose level drops too low to provide enough energy for your body's activities. Patients with severe hypoglycemia may experience unconsciousness or seizures due to low blood sugar.

Hypogonadism—Hypogonadism, or low testosterone, occurs when a man’s testes fail to produce sufficient quantities of testosterone and/or sperm quality is impaired.

Hypothalamus—The hypothalamus is an area of the brain that regulates vital autonomic centers and produces hormones that control thirst, hunger, body temperature, sleep, moods, sex drive, and the release of hormones from various glands, primarily the pituitary gland.

InsulinInsulin is a protein pancreatic hormone involved in the metabolism of carbohydrates and the regulation of glucose levels in the blood. Diabetes occurs when the body doesn’t produce enough insulin or use the hormone effectively.  

IGF-1—IGF-1, or insulin-like growth factor 1, is a polypeptide protein hormone similar in molecular structure to insulin. It plays an important role in childhood growth and continues to have anabolic effects in adults. IGF-1 has been identified as a performance-enhancing drug.

Kallmann Syndrome—Kallmann syndrome is form of hypogonadism that is caused by congenital gonadotropin-releasing hormone (GnRH) deficiency. It is more common in males and is a known cause of delayed puberty

KisspeptinKisspeptin, made in the hypothalamus, starts the reaction that signals the release of hormones involved in testosterone and estradiol production. Also called metastin, this hormone is connected to puberty and fertility, and it may also help stop the spread of cancer.

Klinefelter SyndromeKlinefelter syndrome is the most common congenital abnormality in males causing primary hypogonadism, occurring in approximately 1 in 1000 live male births. This syndrome is the clinical manifestation of a male who has an extra X chromosome.

LeptinLeptin, a hormone released from the fat cells located in adipose tissues, sends signals to the hypothalamus in the brain. This hormone helps regulate and alter long-term food intake and energy expenditure to help the body maintain its weight.

Luteinizing HormoneLuteinizing hormone—also known as lutropin—is necessary for proper reproductive function. In women, it triggers ovulation.

MelatoninMelatonin is essential to signaling the relaxation and lower body temperature that help with restful sleep. Melatonin is created by the pineal gland in the brain.

MenopauseMenopause is the process a woman goes through that causes her monthly periods to end. During menopause, a woman's ovaries stop producing eggs and produce fewer female hormones.

Metabolic SyndromeMetabolic syndrome describes a cluster of metabolic risk factors that increase the chances of developing heart disease, stroke, and diabetes. Genetic factors, too much body fat, and lack of exercise contribute to the development of the condition.

NorepinephrineNorepinephrine is a hormone produced by the adrenal glands. It also acts as a neurotransmitter, a chemical messenger which transmits signals across nerve endings in the body. Together with other hormones, it helps the body respond to stress and exercise.

ObesityObesity is a chronic medical disease of having too much body fat. Health care providers diagnose obesity using a number called the body mass index.

OsteoporosisOsteoporosis is a disease in which bones become weak and are more likely to fracture or break.

OvariesOvaries are the egg producing organs found in females. They produce the hormones estrogen and progesterone.

OxytocinOxytocin is a hormone that acts as a neurotransmitter in the brain. It facilitates birth and breastfeeding.

Pancreas—The pancreas gland secretes insulin, a hormone that helps glucose move from the blood into the cells to be used for energy. The pancreas also secretes glucagon when blood sugar is low.

Parathyroid—The parathyroid gland helps control both calcium and phosphorous levels and are necessary for proper bone development. The parathyroid gland is actually a group of four small glands located behind the thyroid gland.

Parathyroid HormoneParathyroid hormone plays a role in regulating blood calcium levels, helping the body maintain adequate calcium stores in the bloodstream to protect bone health. It comes from four parathyroid glands in the neck, just behind the thyroid.

Peptide YY—After eating, the hormone peptide YY (PYY) is produced by the small intestine and released into the bloodstream. PYY communicates to your brain that you are full and decreases your appetite.

Perimenopause—Part of the menopause transition, the perimenopause stage takes place when a woman’s ovaries gradually begin to produce less estrogen.

Pineal Gland—The pineal is a small endocrine gland located in the center of the brain between the two hemispheres. It secretes melatonin, which helps regulate wake/sleep patterns.

Pituitary Gland—The pituitary is a small endocrine gland located at the base of the skull. It helps control growth, blood pressure, breast milk production, and metabolism.

Polycystic Ovary Syndrome (PCOS)—Polycystic ovary syndrome (PCOS) is common hormone disorder that affects 7 to 10 percent of women. Signs include excess male hormones called androgens, problems with ovulation, and small follicles appearing on the ovaries.

Prader-Willi SyndromePrader-Willi syndrome is a genetic disorder that can cause a growth hormone deficiency. It is marked by a preoccupation with food, small stature, and learning difficulties.

Premenstrual SyndromePremenstrual syndrome describes the appearance of physical and emotional symptoms during the second half of the menstrual cycle.

ProgesteroneProgesterone is a female hormone that signals the uterus to prepare for receiving an egg following fertilization. When progesterone levels go down each month, this causes the bleeding associated with menstrual periods.

Progestin—This is a synthetic form of progesterone. This class of drugs was originally developed to allow absorption by mouth for use in birth control pills.

ProlactinProlactin is a peptide hormone that promotes breast milk production.

ProstaglandinsProstaglandins are a group of lipids involved in the process of inflammation and blood clotting following an injury. These hormones are created during a chemical reaction at the injury site.

RelaxinRelaxin is a reproductive hormone secreted in the ovary by the corpus luteum. It is involved in preparing a pregnant woman’s body for labor and birth.

Serotonin&mdashSerotonin is the key hormone that stabilizes our mood, feelings of well-being, and happiness. It also helps reduce depression, regulate anxiety, and maintain bone health.

SomatostatinSomatostatin—also called SS, SST or SOM—is a growth hormone inhibitory hormone. Somatostatin prevents the production of other hormones and stops the unnatural rapid reproduction of cells—such as those that may occur in tumors.

Steroids—Steroids are any of various molecules—including hormones—that contain a particular arrangement of carbon rings. Some common steroids include sex steroids, corticosteroids, anabolic steroids, and cholesterol.

TestesTestes are the male reproductive organs. They produce sperm and the hormone testosterone.

TestosteroneTestosterone is a steroid, androgen hormone, and the primary male sex hormone. It is produced by the testes in men and ovaries in women, and it plays key roles in libido, energy, and immune function in both men and women.

Thymus—The thymus gland is located in the chest just behind the sternum. The thymus secretes hormones that are commonly referred to as humoral factors and are important during puberty. The role of these hormones is to make sure a person develops a healthy immune system.

Thyroid—The thyroid gland is located inside the neck. It regulates metabolism, which is the body's ability to break down food and convert it to energy. Thyroid disorders typically result when the gland releases too little or too much thyroid hormone.

Thyroid-stimulating hormone—Thyroid-stimulating hormone (TSH) stimulates the thyroid to secrete the hormones thyroxine and triiodothyronine. It is manufactured by the hypothalamus and transported by the anterior pituitary gland.

ThyroxineThyroxine, also known as T4, plays a crucial role in heart and digestive function, metabolism, brain development, bone health, and muscle control. The thyroid gland secretes thyroxine into the bloodstream.

Total testosterone—Total testosterone is a measurement of the total amount of testosterone in the blood, combining free testosterone and testosterone bound to certain molecules and already at use in the body.

Turner SyndromeTurner syndrome occurs in females when one of the X chromosomes is missing or damaged. The most common features of Turner syndrome are short stature and reduced or absent development of the ovaries. As adults, women with this disorder are typically infertile.

Vitamin DVitamin D is a prohormone—a substance the body converts to a hormone. The body produces vitamin D in a chemical reaction that occurs when sunlight hits the skin, and some vitamin D also comes from food sources. Active vitamin D functions as a hormone because it sends messages to the intestines to increase the absorption of calcium and phosphorus.


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