Endocrinology

Adrenal Medullary Hormones 1. Chemistry Belong to the catecholamine group (derived from the amino acid tyrosine ). Water-soluble hormones. Stored in secretory vesicles (chromaffin granules) inside adrenal medulla. Act via adrenergic receptors (α and β receptors) on target tissues. 2. Secretion Secreted by chromaffin cells of the adrenal medulla . Stimulated by sympathetic nervous system (fight-or-flight response). Normal ratio: about 80% epinephrine, 20% norepinephrine . Triggered by stress (fear, anger, hypoglycemia, exercise, trauma, pain). 3. Functions Epinephrine (Adrenaline) Acts mainly on β-adrenergic receptors . Metabolic effects : ↑ Blood glucose (stimulates glycogen breakdown in liver and muscle). ↑ Lipolysis (fat breakdown). Cardiovascular effects : ↑ Heart rate (positive chronotropic effect). ↑ Cardiac output. Dilates skeletal muscle blood vessels (β₂ effect). Respiratory effects : Bronchodilation (helps...

1. Adrenal Cortex – Overview The adrenal gland has two main parts: Adrenal cortex → produces steroid hormones (glucocorticoids, mineralocorticoids, and androgens). Adrenal medulla → produces catecholamines (epinephrine and norepinephrine). We’ll focus on cortical hormones : Glucocorticoids (mainly cortisol in humans) Mineralocorticoids (mainly aldosterone) 2. Chemistry Both glucocorticoids and mineralocorticoids are steroid hormones . Derived from cholesterol through a series of enzymatic reactions. Lipid-soluble, so they can easily cross cell membranes and bind to intracellular receptors . 3. Secretion Glucocorticoids (cortisol) → secreted mainly by the zona fasciculata of the adrenal cortex. Mineralocorticoids (aldosterone) → secreted mainly by the zona glomerulosa of the adrenal cortex. Secretion pattern: Cortisol → shows diurnal rhythm (high in early morning, low at midnight). Aldosterone → secretion depends on renin-angiotens...