The Endocrine System

Positive Feedback

"Vicious cycle." During positive feedback, physiological processes send body chemistry or other attributes further and further away from equilibrium (set point). The trend will continue until something breaks the cycle

Anabolic Steroids

A class of steroids that cause large increases in muscle mass with many side effects

Syndrome of Inappropriate Antidiuretic Hormone (SIADH)

A condition characterized by severe hyponatremia (low blood sodium), usually due to overproduction of ADH regardless of blood osmolarity.

Dwarfism

A condition of being abnormally undersized. May be due to an endocrine condition, heredity, nutritional deficiency, diseases of the skeleton, or others

Cushing's Syndrome

A condition usually the result of the usage of higher levels of corticosteroids in which the patient develops physical features that can include buffalo hump, a rounded face (moon face), weight gain, and increased fragility of the skin

Diabetes Insipidus

A condition with the primary symptoms of frequent urination and thirst caused either by inadequate amounts of circulating vasopressin (antidiuretic hormone) in the body (hypothalamic DI) or by the failure of the kidney to respond to antidiuretic hormone (nephrogenic DI)

Pancreas

A digestive and endocrine organ located in the abdominal cavity that produces digestive enzymes (amylase, lipase, protease, peptidase) and releases them into the duodenum. It also contains the islets of Langerhans (alpha, beta, and delta cells) that produce and secrete the hormones glucagon, insulin, and somatostatin

Graves' Disease

A distinct form of hyperthyroidism that includes an enlarged thyroid gland and various ocular findings such as stare and lid lag.

Anterior Pituitary

A gland controlled by the hypothalamus but also secretes a number of hormones.

Acromegaly

A hormonal condition of gradual coarsening and enlargement of bones and facial features.

Calcitonin

A hormone produced by the human thyroid gland that is important for maintaining a dense, strong bone matrix and regulating the blood calcium level

Antidiuretic Hormone

A hormone secreted by the posterior pituitary gland. It stimulates the kidneys to move water back into the blood to increase the volume of blood

Thyroid Storm

A rare but potentially life-threatening result of untreated hyperthyroidism that can cause cardiac arrhythmias, congestive heart failure, and shock

Addison's Disease

A rare illness marked by gradual, progressive failure of the adrenal glands and by insufficient production of steroid hormones

Steroids

One of the sex hormones and hormones of the adrenal cortex.

Adrenal Cortex

Outermost part of the adrenal gland. It produces and secretes three groups of hormones: mineralocorticoids (aldosterone), glucocorticoids (cortisol), and some androgens (male hormones)

Negative Feedback

Physiological process that works against the trend. Most often brings a variable back to set point. For example, as blood pressure rises, heart rate may decrease to bring blood pressure back to "normal."

Adrenal

Referring to the adrenal gland.

Tetany

Rigid paralysis

Testes

Small, egg-shaped glands in the scrotum. Also known as the testicles. They contain interstitial cells that secrete testosterone. They also contain the seminiferous tubules that produce spermatozoa

Islets Of Langerhans

Specialized group of cells in pancreatic tissue that produce insulin and glucagon

Homeostasis

State of equilibrium of the internal environment of the body, including fluid balance, acid-base balance, temperature, metabolism, and so forth, to keep all the body systems functioning optimally

Hypopituitarism

The underproduction of thyroid hormones, resulting in low metabolism, excessive weight gain, lethargy, and depression

Hypothyroidism

The underproduction of thyroid hormones, resulting in low metabolism, excessive weight gain, lethargy, and depression

Adrenaline

Also known as epinephrine, secreted by the adrenal medulla

Hashimoto's Thyroiditis

An autoimmune disease involving inflammation, then destruction and fibrosis of the thyroid gland, which leads to hypothyroidism

Gigantism

An excessive development of a body or body part often as a result of an abnormal hormone level

Posterior Pituitary

An extension of the hypothalamus that secretes oxytocin and ADH

Endocrine System

Body system that includes the testes, ovaries, pancreas, adrenal glands, thymus, thyroid gland, parathyroid glands, pituitary gland, and pineal gland. It produces and releases hormones into the blood to direct the activities of other body organs.

Hormones

Chemical messenger of the endocrine system that is released by a gland or organ and travels through the blood.

Adrenocorticosteroids

Collective term for numerous hormones secreted by the adrenal cortex

Diabetes Mellitus (DM)

Condition resulting from too little secretion of insulin leading to increased levels of blood glucose

Congenital Hypothyroidism

Hypothyroidism present at birth

Adrenal Medulla

Innermost part of the adrenal gland. It produces and secretes the hormones epinephrine and norepinephrine

Thymus Gland

Lymphoid organ in the thoracic cavity. As an endocrine gland, it releases hormones known as thymosins. Thymosin causes lymphoblasts in the thymus to mature into T lymphocytes.

Glucocorticoids

Hormones produced by the adrenal cortex that regulate blood sugar

Pituitary

Endocrine gland in the brain that is connected by a stalk of tissue to the hypothalamus. Also known as the hypophysis. It is known as the master gland of the body. It consists of the anterior and the posterior pituitary gland

Pineal Gland

Endocrine gland in the brain that lies posterior to the pituitary gland. It secretes the hormone melatonin

Thyroid

Endocrine gland in the neck that produces and secretes the hormones T3, T4, and calcitonin. Its two lobes and narrow connecting bridge (isthmus) give it a shieldlike shape.

Hypothalamus

Endocrine gland located in the brain just below the thalamus. It produces (but does not secrete) antidiuretic hormone (ADH) and oxytocin. The hypothalamus is in the center of the brain and coordinates the activities of the pons and medulla oblongata. It also controls heart rate, blood pressure, respiratory rate, body temperature, sensations of hunger and thirst, and the circadian rhythm. It also produces hormones as part of the endocrine system. In addition, the hypothalamus helps control emotions (pleasure, excitement, fear, anger, sexual arousal) and bodily responses to emotions; regulates the sex drive; contains the feeding and satiety centers; and functions as part of the "fight-or-flight" response of the sympathetic nervous system.

Parathyroid Glands

Endocrine glands, four of them, on the posterior lobes of the thyroid gland. They produce and secrete parathyroid hormone.

Goiter

Enlargement of the thyroid gland.

Mineralocorticoids

Hormones secreted by the adrenal cortex that regulate electrolytes, salts, and fluid balance

Exocrine

Glands and organs that excrete through a duct

Hypercholesterolemia

High levels of cholesterol in the blood

Triiodothyronine

Hormone T3 secreted by the thyroid gland

Thyroxine

Hormone T4 secreted by the thyroid gland

Humoral Control

Hormone levels controlled by body fluids such as blood

Hormonal Control

Hormone levels controlled by other hormones.

Epinephrine

Hormone secreted by the adrenal medulla in response to stimulation by nerves of the sympathetic nervous system

Norepinephrine

Hormone secreted by the adrenal medulla in response to stimulation by nerves of the sympathetic nervous system.

Prolactin

Hormone secreted by the anterior pituitary gland. It stimulates milk glands of the breasts to develop during puberty and to produce milk during pregnancy

Insulin

Hormone secreted by the pancreas that allows for glucose to be utilized for cellular respiration.

Glucagon

Hormone secreted by the pancreas that increases the blood glucose by stimulating the liver to change stored glycogen to glucose.

Parathyroid Hormone (PTH)

Hormone secreted by the parathyroid glands that regulates levels of calcium in the bloodstream

Melatonin

Hormone secreted by the pineal body. It maintains the 24-hour wake-sleep cycle known as the circadian rhythm

Oxytocin

Hormone secreted by the posterior pituitary gland. It stimulates the uterus to contract and begin labor. It stimulates the "let-down reflex" to get milk flowing for breastfeeding

Thymosin

Hormone secreted by the thymus gland that helps white blood cells mature during childhood.

Glycogen

The form that glucose (sugar) takes when it is stored in the liver and skeletal muscles

Neural Control

The nervous system control of hormone levels.

Set Point

The normal physiologic range (as in body temperature and blood pressure) to maintain homeostasis

Hyperthyroidism

The overproduction of thyroid hormones, often resulting in increased metabolic rate, weight loss, and nervous irritability