Endocrine System Overview and Hormones

Vocabulary practice flashcards defining key hormones, structures, and processes of the human endocrine system.

Cortisol

The primary stress hormone that triggers the fight-flight-or-freeze response, produced by the zona fasciculata of the adrenal cortex.

Thymus gland

An organ that produces T-cells for the immune system and secretes hormones including thymosin and thymopoeitin.

Melanocyte-stimulating hormone (MSH)

A tropic hormone from the adenohypophysis targeting melanocytes; hypersecretion causes increased melatonin production and hyposecretion causes decreased melatonin production.

Follicle-stimulating hormone (FSH)

A tropic hormone from the adenohypophysis stimulated by GnRH that targets the ovaries and testes; hyposecretion leads to failure of sexual maturation.

Luteinizing hormone (LH)

A tropic hormone from the adenohypophysis stimulated by GnRH that targets the ovaries and testes; hyposecretion leads to failure of sexual maturation.

Adrenocorticotropic hormone (ACTH)

A tropic hormone from the adenohypophysis targeting the adrenal cortex; hypersecretion leads to Cushing's Syndrome/Disease and hyposecretion is very rare.

Thyroid-stimulating hormone (TSH)

A tropic hormone from the adenohypophysis targeting the thyroid gland; hypersecretion leads to hyperthyroidism and hyposecretion leads to cretinism in children and myxedema in adults.

Prolactin (PRL)

A non-tropic hormone from the adenohypophysis targeting breast secretory tissue; hypersecretion causes galactorrhea, cessation of menses in females, and impotence in males, while hyposecretion causes poor milk production in nursing women.

Growth hormone (GH)

A non-tropic hormone targeting the liver, bones, cartilage, and other tissues, stimulated by GHRH release; hypersecretion causes gigantism in children and acromegaly in adults, while hyposecretion causes pituitary dwarfism in children.

Oxytocin (OT)

A neurohypophysis hormone targeting the uterus, originating from neurons in the paraventricular nucleus of the hypothalamus.

Antidiuretic hormone (ADH)

Also known as vasopressin, a neurohypophysis hormone originating from neurons in the supraoptic nucleus of the hypothalamus that targets the kidneys to absorb water; hypersecretion causes SIADH and high blood pressure, hyposecretion causes reduced urinary output, and it is inhibited by alcohol.

Paraventricular nucleus

The specific region in the hypothalamus containing the neurons from which oxytocin (OT) originates.

Supraoptic nucleus

The specific region in the hypothalamus containing the neurons from which antidiuretic hormone (ADH) originates.

Calcium homeostasis

The balance of normal blood calcium at approximately $\sim 10\,mg/100\,mL$; high blood calcium triggers calcitonin release from the thyroid, while low blood calcium triggers PTH release from the parathyroid.

Calcitonin

A hormone released by the thyroid gland during high blood calcium levels that stimulates reduction of calcium uptake in the intestines and kidneys and stimulates calcium deposits in bones.

Parathyroid hormone (PTH)

A hormone released by the parathyroid gland during low blood calcium levels that stimulates increased calcium uptake in the kidneys and intestines and stimulates calcium release from bones.

Zona glomerulosa

The outermost region of the adrenal cortex that produces mineralocorticoids, such as aldosterone.

Zona fasciculata

The middle region of the adrenal cortex that produces glucocorticoids, such as cortisol.

Zona reticularis

The innermost region of the adrenal cortex that produces gonadocorticoids, such as androgen.

Adrenal medulla

The inner part of the adrenal gland that produces catecholamines, specifically norepinephrine and epinephrine.

Gene activation of lipid-soluble hormones

A 5-step process: 1) Steroid hormone diffuses through plasma membrane to bind to an intracellular receptor, 2) Receptor-hormone complex enters nucleus, 3) Complex binds to a hormone response element on DNA, 4) Binding initiates gene transcription, 5) mRNA directs protein synthesis.

Humoral stimulus

Hormone release caused by altered levels of critical ions or nutrients, such as low concentration of calcium in blood stimulating parathyroid gland secretion of PTH.

Neural stimulus

Hormone release triggered by neural input, such as action potentials in preganglionic fibers stimulating the adrenal medulla to secret epinephrine and norepinephrine.

Hormonal stimulus

Hormone release caused by another hormone (tropic hormone), such as hypothalamic hormones causing the adenohypophysis to secrete hormones that stimulate another endocrine gland.

Tropic hormone

Also called a tropin, a hormone that influences another endocrine gland, stimulating it to release its own hormone in response to a stimulus; examples include TSH, ACTH, FSH, LH, and MSH.

Principal/chief cells

Cells located in the parathyroid glands that function to secrete parathyroid hormone (PTH).

Oxyphil cells

A type of cell found within the parathyroid glands alongside principal/chief cells.

Suprarenal gland

Another term for the adrenal gland.

Cushing's Syndrome

A condition resulting from elevated ACTH/cortisol characterized by a 'buffalo hump' of fat on upper back, persistent elevated blood glucose, loss of bone and muscle mass, hypertension, and edema.

Triiodothyronine ($T_3$) and Thyroxine ($T_4$)

Thyroid hormones that regulate lipid and protein metabolisms, increase protein synthesis rate, accelerate energy release from carbs, accelerate growth and development, and stimulate nervous system activity.

Adrenal short-term stress response

A physiological response involving increased heart rate and blood pressure, bronchiole dilation, conversion of glycogen to glucose by the liver, decreased digestive/urinary output, and increased metabolic rate.

Adrenal long-term stress response

A physiological response involving kidney retention of water and sodium, rising blood volume/pressure, elevated blood glucose, immune system suppression, and breakdown of proteins and fats for energy.

Glycogenesis

The process of converting Glucose to Glycogen facilitated by insulin.

Glycogenolysis

The process of converting Glycogen to Glucose facilitated by cortisol and glucagon.

Gluconeogenesis

The formation of new glucose from lactic acid and amino acids facilitated by cortisol.

Glycolysis

The chemical breakdown of glucose into pyruvates.

Atrial natriuretic peptide (ANP)

Also known as Atrial natriuretic factor (ANF), a hormone secreted by the atria of the heart.

Erythropoietin (EPO)

A kidney hormone with increased production triggered when tissues require more oxygen.

Cholecalfiferol (provitamin D2)

A non-endocrine hormone/compound associated with the skin.

Duodenum hormones

Hormones produced by the small intestine (duodenum), including Intestinal gastrin, Secretin, and Cholecystikinin (CCK).