Endocrine Vocabulary

Endocrine Cells & Hormones

• Acidophil cells that stain with acid dyes ex Anterior pituitary cells that secrete growth hormone (GH) and pr: Anterior pituitary cellsThe basic structural and functional units of life. that stain with acidA substance that releases hydrogen ions (H⁺) in solution. dyes and secrete growth hormone(GH): Stimulates growth and metabolism. (GH) and prolactin(PRL): Promotes milk production. (PRL).
• Basophilcells that stain with basic dyes Anterior pituitary that secrete FSH, LH, TSH, and ACTH.: Anterior pituitary cells that stain with basicA solution with a pH above 7, having a lower concentration of H⁺ ions. dyes and secrete FSH, LH, TSH, and ACTH.
• Alpha cellPancreatic islet cells that secrete glucagon to raise blood glucose.: Pancreatic islet cells that secrete glucagonIncreases blood sugar by promoting glycogen breakdown. to raise blood glucoseA simple sugar that is the main source of energy for cells..
• Beta cells: Pancreatic islet cells that secrete insulin to lower blood glucose.
• Delta cellsPancreatic islet cells that secrete somatostatin, which inhibits insulin and glucagon secretion.: Pancreatic islet cells that secrete somatostatinInhibits GH, insulin, and glucagon secretion., which inhibits insulin and glucagon secretionThe process of moving substances from the blood into the nephron tubule to be excreted in urine..
• C (clear) cells: Thyroid parafollicular cells that secrete calcitoninA hormone from the thyroid that lowers blood calcium levels by inhibiting osteoclasts..
• Corticotropic cells: Anterior pituitary cells that produce ACTH.
• Gonadotropic cells: Pituitary cells that secrete FSH and LH.
• Prolactin cells: Anterior pituitary cells that secrete prolactin (PRL).
• Somatotropic cells: Anterior pituitary cells that secrete growthAn increase in size and number of cells. hormone (GH).

Endocrine Organs & Structures

• Adrenal cortex: Outer portion of the adrenal glands producing corticosteroidsSteroid hormones from the adrenal cortex, including glucocorticoids and mineralocorticoids..
• Adrenal glands: Paired endocrine glands above the kidneys producing stress-related hormones.
• Adrenal medulla: Inner part of adrenal glands producing catecholamines (epinephrineadrenaline): Fight-or-flight hormone from the adrenal medulla., norepinephrineA neurotransmitter involved in attention, arousal, and the fight-or-flight response.).
• Anterior pituitary glandEndocrine gland at the brain’s base controlling many hormones. (APG): Endocrine gland producing GH, PRL, TSH, ACTH, FSH, and LH.
• Parathyroid gland: Small glands on the thyroid that secrete PTH to regulate calcium.
• Pineal gland: Small brain structure that secretes melatoninRegulates sleep-wake cycles..
• Pituitary gland: Endocrine gland at the brain’s baseA substance that accepts hydrogen ions (H⁺) or releases hydroxide ions (OH⁻). controlling many hormones.
• Posterior pituitary gland (PPG): Stores and releases oxytocin(OXT): Stimulates uterine contractions and milk ejection. and ADH produced by the hypothalamusA small but vital brain region controlling hormones, temperature, and autonomic functions..
• Thyroid gland: Endocrine gland regulating metabolismThe sum of all chemical reactions in the body. through thyroid hormones.

Hormones & Their Functions

• Adrenocorticotropic hormone (ACTH): Stimulates adrenal cortexOuter portion of the adrenal glands producing corticosteroids. to release corticosteroids.
• Aldosterone: A mineralocorticoid regulating sodium(Na⁺): Major ECF cation; important for fluid balance, nerve function. and potassium(K⁺): Major ICF cation; essential for muscle and nerve function. balance.
• Amylin: Hormone secreted with insulin to slow glucose absorption.
• Androgens: Male sex hormones, including testosterone and DHEA.
• Antidiuretic hormone (ADH): Increases waterThe universal solvent essential for life. retention by kidneys.
• Calcitonin: Lowers blood calcium levels by stimulating bone depositionThe process of bone matrix formation by osteoblasts..
• Corticosteroids: Steroid hormones from the adrenal cortex, including glucocorticoidsSteroid hormones regulating metabolism and immune response. and mineralocorticoidsRegulate electrolyte and water balance (e.g., aldosterone)..
• Corticotropin-releasing hormone (CRH): Stimulates ACTH release.
• Cortisol: A glucocorticoid involved in stress response, metabolism, and immune regulation.
• Dehydroepiandrosterone (DHEA): Weak androgen precursor to testosterone and estrogen.
• Dopamine: Neurotransmitter and prolactin-inhibiting hormone (PIH).
• Epinephrine (adrenaline): Fight-or-flight hormone from the adrenal medullaInner part of adrenal glands producing catecholamines (epinephrine, norepinephrine)..
• Estradiol: Primary estrogen regulating female reproductive functions.
• Follicle-stimulating hormone (FSH): Stimulates ovarian follicle growth and sperm production.
• Glucagon: Increases blood sugar by promoting glycogenA storage form of glucose found in animals. breakdown.
• Glucocorticoids: Steroid hormones regulating metabolism and immune response.
• Gonadotropin-releasing hormone (GnRH): Stimulates FSH and LH release.
• Gonadotropins: Hormones (FSH, LH) that regulate reproductive organs.
• Growth hormone (GH): Stimulates growth and metabolism.
• Growth hormone-releasing hormone (GHRH): Stimulates GH secretion.
• Insulin-like growth factors (IGFs): Mediate growth hormone effects on tissues.
• Luteinizing hormone (LH): Triggers ovulationThe release of a mature oocyte from the ovary. and testosterone production.
• Melatonin: Regulates sleep-wake cycles.
• Mineralocorticoids: Regulate electrolyte and water balance (e.g., aldosteroneA hormone that increases sodium and water reabsorption in the kidneys, helping regulate blood pressu).
• Norepinephrine: Neurotransmitter and adrenal medulla hormone involved in stress responses.
• Oxytocin (OXT): Stimulates uterine contractions and milk ejection.
• Parathyroid hormone (PTH): Raises blood calcium by stimulating bone resorption.
• Prolactin (PRL): Promotes milk production.
• Releasing hormones: Hypothalamic hormones that regulate pituitary gland secretions.
• Somatostatin: Inhibits GH, insulin, and glucagon secretion.
• Thyroid hormone (TH): Includes T3 and T4, regulating metabolism.
• Thyroid-releasing hormone (TRH): Stimulates TSH and PRL release.
• Thyroid-stimulating hormone (TSH): Stimulates thyroid hormone (TH): Includes T3 and T4, regulating metabolism. production.
• Triiodothyronine (T3): Active form of thyroid hormone.
• Tetraiodothyronine (T4, thyroxine): Precursor to T3.

Hormone Regulation & Transport

• Bound hormone: Hormone attached to a transport protein in the bloodstream.
• Unbound hormone: Free hormone active in the bloodstream.
• Half-life: Time for hormone levels to reduce by half.
• Hormonal stimuliChanges in the environment that are detected by sensory receptors.: Hormone secretion triggered by other hormones.
• Humoral stimuli: Hormone secretion triggered by changes in blood levels of ionsCharged atoms or molecules. or nutrients.
• Neural stimuli: Hormone secretion triggered by nervous systemThe organ system that controls body functions using electrical and chemical signals. signals.
• Negative feedback inhibition: Hormone regulation where high levels inhibit further secretion.
• Permissive effect: When one hormone enhances the effects of another.
• Synergistic effects: When two hormones amplify each other’s effects.
• Antagonistic effects: When one hormone opposes another’s effect.

Hormone Transport & Cell Signaling

• Calmodulin: Protein that binds calcium to activate cellular processes.
• cAMP(Cyclic AMP): Second messenger in many hormone signaling pathways. (Cyclic AMP): Second messenger in many hormone signaling pathways.
• CatecholaminesNeurotransmitters derived from tyrosine: dopamine, norepinephrine, and epinephrine.: Includes epinephrine, norepinephrine, and dopamineA catecholamine neurotransmitter involved in motor control, motivation, and reward..
• Chromaffin cells: Adrenal medulla cells that secrete catecholamines.
• Chromophobes: Pituitary cells that do not stain well and have unclear function.
• Ghrelin: Hunger hormone from the stomach.
• Glucose-sparing effect: GH and cortisolA glucocorticoid involved in stress response, metabolism, and immune regulation. reducing glucose usage to save it for the brain.
• Glycogenolysis: Breakdown of glycogen into glucose.
• Glycemia: Blood glucose concentration.
• Signal amplification: When one hormone molecule triggers many intracellular responses.
• Transport proteinsLarge molecules made of amino acids with various functions in the body.: Bind hormones for transport in the blood.

Other Structures & Functions

• Exocrine: Glands that secrete substances via ducts (e.g., sweat glands).
• Gap junctionsCell connections that allow ion flow between adjacent muscle cells.: Direct cell-to-cell communication channelsProtein passages in the cell membrane that allow specific molecules to pass through..
• Hypophyseal portal system: Blood vessel network connecting hypothalamus to anteriorThe front of the body or toward the front when standing in the anatomical position. pituitary.
• Hypothalamic-hypophyseal portal tract: Nerve fibers connecting the hypothalamus to the posterior pituitary.
• Infundibulum: Stalk connecting hypothalamus to the pituitary gland.
• Osmoreceptors: Hypothalamic cells detecting blood osmolarityA measure of solute concentration in fluid; affects fluid movement between compartments. to regulate ADH.
• Pancreas: Organ with both endocrine (insulin, glucagon) and exocrineGlands that secrete substances via ducts (e.g., sweat glands). (digestive enzymesProteins that speed up chemical reactions in the body.) functions.
• Paracrine: Local hormone-like moleculesGroups of atoms bonded together. affecting nearby cells.
• Target cells: Cells with specific receptorsProteins located on the surface or inside cells that bind specific molecules (e.g., neurotransmitter for a hormone.
• Target organs: Organs affected by specific hormones.

Albumin: A plasmaThe liquid component of blood. protein that binds and transports hormones in the blood, holding a reserve of bound hormoneHormone attached to a transport protein in the bloodstream. alongside the free, active fraction.

Calorigenic effect: The rise in metabolic rate and heat production caused by thyroid hormone.

Down-regulation: A fall in the number of target-cell receptors after prolonged exposure to high hormone levels, making the cell less sensitive.

Up-regulation: A rise in the number of target-cell receptors when hormone levels are low, making the cell more sensitive.

Endocrine glands: Ductless glands that secrete hormones directly into the bloodstream.

Follicular cells: The cells forming the wall of a thyroid follicle; they make thyroglobulin, the precursor of T3 and T4.

Parafollicular cells: Thyroid cells lying between the folliclesStructures in the ovaries that contain developing oocytes. that secrete calcitonin; also called C cells.

Thyroid follicles: The hollow spheres of follicular cellsCells surrounding the oocyte that support its development. filled with colloidA mixture where small particles are dispersed but not dissolved in a liquid. that make up the bulk of the thyroid gland Endocrine gland regulating metabolism through thyroid hormones..

Thyroglobulin: The large protein made by follicular cells and stored in thyroid colloid; T3 and T4 are cleaved from it.

Isthmus: The narrow bridge of thyroid tissue connecting the gland’s right and left lobes across the front of the trachea.

Hypothalamic-pituitary-thyroid axisSecond cervical vertebra; has the odontoid process (dens) for pivoting head (“no” motion).: The control loop in which the hypothalamus releases TRH, the anterior pituitary releases TSH, and the thyroid releases T3 and T4, which feed back to shut the loop down.

Thyrotropic cells: Anterior pituitary cells that secrete thyroid-stimulating hormone (TSH): Stimulates thyroid hormone production. (TSH).

Thyroxine-binding globulin: The main plasma protein that carries thyroid hormone through the blood.

Transthyretin: A plasma protein that transports thyroid hormone and vitamin A.

Transcortin: The plasma protein that carries cortisol and other corticosteroids through the blood.

Gluconeogenesis: The making of new glucose from non-carbohydrate sources such as amino acids and glycerol.

Hormones: Chemical messengers secreted into the blood that act only on cells carrying the matching receptorA structure that detects stimuli..

Inhibiting hormones: Hypothalamic hormones that travel to the anterior pituitary and suppress release of a specific pituitary hormone.

Prolactin-inhibiting hormone (PIH): The hypothalamic signal — dopamine — that holds prolactin secretion in check.

Metabolic clearance rate: The rate at which a hormone is removed from the blood by the liverA large organ that produces bile, detoxifies blood, and stores nutrients., kidneys and target tissues.

Monoamines: Hormones built from a single amino acidThe building blocks of proteins, consisting of an amino group, carboxyl group, and side chain., usually tyrosine; they include thyroid hormone and the catecholamines.

Peptides: Hormones built from short chains of amino acids; being water-soluble, they bind receptors on the target cell’s surface.

Steroids: Hormones derived from cholesterolA lipid molecule that is a key component of cell membranes and a precursor for bile acids and steroi; being lipid-soluble, they pass through the membrane and bind receptors inside the cell.

Sex steroids: The steroid hormones driving reproductive developmentThe process of growth and differentiation. and function: androgensMale sex hormones, including testosterone and DHEA., estrogensFemale sex hormones responsible for secondary sex characteristics and regulation of the menstrual cy and progesteroneA hormone that supports pregnancy and regulates the menstrual cycle..

Neuroendocrine cells: Neurons that release their product into the bloodstream as a hormone rather than into a synapseThe junction between two neurons where communication occurs..

Neuroendocrine reflexesAutomatic responses to stimuli.: Hormone release triggered by a nervous-system signal, such as the milk-ejection reflex.

Neurotransmitters: Chemical messengers released by a neuron that act across a synapse on the immediately adjacent cell.

Pancreatic islets: Clusters of endocrine cells scattered through the pancreasA gland that produces digestive enzymes and hormones like insulin and glucagon. (the islets of Langerhans) that secrete insulin, glucagon, somatostatin and pancreatic polypeptide.

Pancreatic polypeptide: A hormone from the PP cells of the pancreatic islets that moderates appetite and pancreatic secretion.

PP cells: Pancreatic islet cells that secrete pancreatic polypeptide.

Paraventricular nucleiClusters of neurons in the CNS responsible for processing information.: Hypothalamic nuclei whose neuronsThe functional cells of the nervous system that transmit signals. produce oxytocin for release from the posterior pituitary.

Supraoptic nuclei: Hypothalamic nuclei whose neurons produce antidiuretic hormoneADH A hormone that increases water reabsorption in the kidneys to concentrate urine and reduce water for release from the posterior pituitary.

Phosphodiesterase: The enzyme that breaks down cAMP, switching off a second-messenger response.

Protein-sparing effect: The action of growth hormone and insulin in promoting protein synthesis while steering the body to burn fat rather than protein for fuel.

Saturation: The point at which every available receptor or transport protein is occupied, so more hormone produces no further effect.

Somatomedins: Liver-produced growth factors — the insulin-like growth factors(IGFs): Mediate growth hormone effects on tissues. — through which growth hormone acts on tissues.

Adrenal Cortex Zones

• Zona fasciculata: Middle adrenal cortex layer, secreting glucocorticoids.
• Zona glomerulosa: Outer adrenal cortex layer, secreting aldosterone.
• Zona reticularis: Inner adrenal cortex layer, producing androgens.