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