Endocrine System & Hormone Vocabulary

Vocabulary flashcards summarizing key endocrine glands, hormones, axes, and regulatory concepts from the lecture notes.

Endocrine System

A network of ductless glands that secrete hormones into the bloodstream to regulate body functions.

Hormone

A chemical messenger released by an endocrine cell that travels through blood to affect distant target cells.

Target Cell

A cell whose membrane or intracellular receptors bind a specific hormone and initiate a response.

Tropic Hormone

A hormone that stimulates another endocrine gland to secrete its hormones.

Homeostasis

The dynamic maintenance of a stable internal environment by physiological processes.

Pituitary Gland

The master endocrine gland located in the sella turcica; consists of anterior and posterior lobes.

Anterior Pituitary (Adenohypophysis)

Glandular lobe of the pituitary that synthesizes and releases tropic hormones such as TSH, ACTH, FSH, LH, GH, and PRL.

Posterior Pituitary (Neurohypophysis)

Neural lobe of the pituitary that stores and releases ADH and oxytocin produced by the hypothalamus.

Hypothalamus

Brain region that links nervous and endocrine systems; controls pituitary secretion via releasing/inhibiting hormones.

Infundibulum

The stalk of tissue that connects the hypothalamus to the pituitary gland.

Pineal Gland

Small epithalamic gland that secretes melatonin to regulate circadian rhythms.

Melatonin

Pineal hormone that promotes sleep and helps set the body’s sleep–wake cycle.

Thyroid Gland

Butterfly-shaped gland anterior to the trachea that produces T3, T4, and calcitonin.

Follicular Cells

Thyroid epithelial cells lining follicles; synthesize thyroxine (T4) and triiodothyronine (T3).

Parafollicular (C) Cells

Cells between thyroid follicles that secrete calcitonin to lower blood calcium.

Thyroxine (T4)

Iodine-containing thyroid hormone with four iodines; increases metabolic rate.

Triiodothyronine (T3)

More active thyroid hormone with three iodines; elevates cellular metabolism.

Calcitonin

Thyroid hormone that decreases blood calcium by stimulating bone deposition.

Parathyroid Glands

Four small glands on posterior thyroid that release parathyroid hormone.

Parathyroid Hormone (PTH)

Hormone that raises blood calcium by stimulating bone resorption and renal reabsorption.

Hypothalamic–Pituitary–Thyroid (HPT) Axis

Hormone cascade: TRH → TSH → thyroid hormones; regulates metabolism and temperature.

Hyperthyroidism

Condition of excess thyroid hormone leading to high metabolism, heat intolerance, weight loss.

Graves’ Disease

Autoimmune hyperthyroidism characterized by excess T3/T4 and exophthalmos.

Thyroid-Stimulating Hormone (TSH)

Anterior pituitary tropic hormone that prompts the thyroid to release T3 and T4.

Adrenocorticotropic Hormone (ACTH)

Anterior pituitary hormone that stimulates cortisol release from adrenal cortex.

Growth Hormone (GH)

Anterior pituitary hormone that promotes tissue growth, protein synthesis, and raises blood glucose.

Prolactin (PRL)

Anterior pituitary hormone that stimulates milk production in mammary glands.

Follicle-Stimulating Hormone (FSH)

Anterior pituitary hormone that initiates gamete production in ovaries and testes.

Luteinizing Hormone (LH)

Anterior pituitary hormone triggering ovulation and testosterone secretion.

Antidiuretic Hormone (ADH)

Posterior pituitary hormone that promotes water reabsorption in kidneys, reducing urine output.

Oxytocin

Posterior pituitary hormone causing uterine contractions and milk ejection.

Adrenal Glands

Paired glands atop kidneys consisting of cortex and medulla with distinct hormones.

Adrenal Cortex

Outer adrenal layer producing mineralocorticoids, glucocorticoids, and gonadocorticoids.

Zona Glomerulosa

Superficial cortical zone that secretes mineralocorticoids (e.g., aldosterone).

Mineralocorticoids

Adrenal hormones regulating electrolyte and fluid balance; chief example is aldosterone.

Aldosterone

Mineralocorticoid that increases Na⁺ retention and K⁺ excretion in kidneys, raising blood volume.

Zona Fasciculata

Middle cortical zone that secretes glucocorticoids such as cortisol.

Glucocorticoids

Hormones that help resist stress by raising blood glucose and reducing inflammation.

Cortisol

Major glucocorticoid involved in stress response, metabolism, and anti-inflammatory actions.

Zona Reticularis

Deep cortical zone that produces small amounts of gonadocorticoids (androgens).

Gonadocorticoids

Weak adrenal androgens that supplement sex hormones from gonads.

Adrenal Medulla

Inner adrenal region of neuroendocrine tissue that secretes catecholamines.

Epinephrine

Adrenal medulla catecholamine (adrenaline) that increases heart rate and blood glucose in stress.

Norepinephrine

Catecholamine that constricts blood vessels and reinforces sympathetic responses.

Hypothalamic–Pituitary–Adrenal (HPA) Axis

Stress hormone cascade: CRH → ACTH → cortisol; integrates nervous and endocrine stress responses.

Corticotropin-Releasing Hormone (CRH)

Hypothalamic peptide triggering ACTH release from anterior pituitary.

Fight-or-Flight Response

Acute stress reaction coordinated by sympathetic nerves and adrenal hormones for survival.

Pancreas

Mixed gland with exocrine digestive acini and endocrine islets regulating blood glucose.

Islets of Langerhans

Clusters of endocrine cells in the pancreas containing alpha and beta cells.

Alpha Cells

Pancreatic islet cells that secrete glucagon to raise blood glucose levels.

Glucagon

Pancreatic hormone that stimulates glycogen breakdown and hepatic glucose release.

Beta Cells

Pancreatic islet cells that secrete insulin to lower blood glucose levels.

Insulin

Hormone promoting cellular uptake of glucose and storage as glycogen or fat.

Diabetes Mellitus

Disorder of insulin deficiency or resistance causing chronic hyperglycemia.

Gonads

Primary reproductive organs (ovaries or testes) that produce gametes and sex hormones.

Ovaries

Female gonads that produce oocytes, estrogen, and progesterone.

Estrogen

Ovarian steroid that promotes female secondary sex characteristics and uterine growth.

Progesterone

Ovarian hormone that prepares uterus for implantation and maintains pregnancy.

Testes

Male gonads producing sperm and testosterone.

Testosterone

Primary male androgen responsible for male secondary sex traits and sperm production.

Thymus

Immune organ in mediastinum that trains T lymphocytes; most active in childhood.

Thymosin

Thymic hormone group that promotes maturation of T cells for immune defense.

T Lymphocyte (T Cell)

White blood cell that matures in the thymus and mediates cellular immunity.

Negative Feedback

Control mechanism in which rising hormone levels inhibit further hormone release, maintaining balance.