Overview
This lecture covers the structure, function, and hormone secretion of the adrenal (suprarenal) glands, including related diseases and mechanisms regulating hormone release.
Adrenal Gland Structure
- The adrenal (suprarenal) glands sit atop the kidneys and consist of two main parts: the cortex (outer) and medulla (inner).
- The adrenal cortex has three layers: zona glomerulosa, zona fasciculata, and zona reticularis.
- The adrenal medulla is the innermost part and is controlled by the sympathetic nervous system.
Adrenal Cortex Hormones
- Zona glomerulosa releases mineralocorticoids, mainly aldosterone.
- Zona fasciculata releases glucocorticoids, mainly cortisol.
- Zona reticularis releases gonadocorticoids, mainly androgens (precursors to testosterone and estrogen).
- Mnemonic: "The deeper you go, the sweeter it is" (Salt, Sugar, Sex: aldosterone, cortisol, androgens).
Functions of Aldosterone
- Aldosterone raises blood pressure by increasing sodium reabsorption (water follows sodium), boosting blood volume.
- Promotes potassium secretion into urine to balance charge.
- Stimuli for aldosterone: high blood potassium, low sodium, low blood pressure, ACTH, and renin-angiotensin-aldosterone system.
- Inhibited by atrial natriuretic peptide (ANP) from the heart.
- Too much aldosterone causes hypertension and low potassium (Conn’s disease); too little causes hypotension and high potassium.
Functions of Cortisol
- Cortisol helps the body respond to stress by rapidly increasing blood glucose.
- Stimulates gluconeogenesis, fat breakdown, and muscle protein breakdown.
- Causes vasoconstriction (raises blood pressure) and suppresses the immune system.
- Excess cortisol—Cushing’s syndrome: high glucose, hypertension, trunk obesity, muscle wasting, and moon face.
- Deficiency—Addison’s disease: low glucose, weight loss, muscle weakness, hypotension, tan skin, and high potassium.
Functions of Androgens
- Androgens are precursors to testosterone; contribute to secondary sex traits in males and libido in females.
- In females, androgens can convert to estrogen, especially if ovaries are removed.
Adrenal Medulla
- Releases epinephrine and norepinephrine (catecholamines) during stress (“fight or flight”).
- Tumor (pheochromocytoma) causes excessive catecholamine release, hypertension, and headaches.
Additional Endocrine Organs/Hormones
- Ovaries produce estrogen and progesterone for reproduction.
- Testes produce testosterone for male traits.
- Heart produces ANP to inhibit aldosterone and reduce blood pressure.
- Kidneys release erythropoietin (increase red cells) and renin (raises blood pressure).
- Placenta produces beta-HCG (pregnancy hormone).
- Adipose (fat) tissue releases leptin to increase hunger.
Key Terms & Definitions
- Adrenal Gland — endocrine gland on top of the kidney, split into cortex and medulla.
- Aldosterone — mineralocorticoid controlling sodium/water reabsorption and potassium excretion.
- Cortisol — glucocorticoid managing stress response, glucose, and immune function.
- Androgen — hormone precursor to testosterone and estrogen.
- Epinephrine/Norepinephrine — catecholamines for quick stress ("fight or flight") response.
- Conn’s Disease — excess aldosterone causing hypertension and hypokalemia.
- Cushing’s Syndrome — excess cortisol causing hyperglycemia and central obesity.
- Addison’s Disease — deficient cortisol/aldosterone causing hypotension and hyperpigmentation.
- Atrial Natriuretic Peptide (ANP) — heart hormone inhibiting aldosterone, lowering blood pressure.
- Renin-Angiotensin-Aldosterone System (RAAS) — pathway increasing blood pressure via aldosterone.
Action Items / Next Steps
- Review and memorize adrenal cortex layers and their hormone products.
- Make flashcards or charts to organize hormones, sources, and effects.
- Know disease symptoms from hormone excess or deficiency.
- Read about the RAAS mechanism and review hormone flowcharts at home.