Related Subjects:
|Adrenal Physiology
|Addisons Disease
|Phaeochromocytoma
|Adrenal Adenomas
|Adrenal Cancer
|Cushing Syndrome
|Cushing Disease
|Congenital Adrenal hyperplasia
|Primary hyperaldosteronism (Conn's syndrome)
|ACTH
|McCune Albright syndrome
Aide memoir - GFR for Glomerulosa (Mineralocorticoids = aldosterone), Fasiculata (cortisol), Reticularis (androgens)
About
- Composed of medulla 10% and cortex 90%
- Also called suprarenal and are found above the kidneys
- Arterial supply from renal arteries
- Venous drainage to IVC on the right and Renal vein on left
- Involved in blood pressure control and steroid production
Diagram
Adrenal Cortex Structuire
- Glomerulosa: Mineralocorticoid aldosterone - Na uptake and K release
- Fasiculata (Cortisol) : affect carbohydrate, lipid and protein metabolism
- Reticularis (androgens) : weak until converted peripherally into testosterone
and dihydrotestosterone
Biochemistry
- All steroids hormones are formed from cholesterol
- Cholesterol is released from lipids by cholesterol esterase (+ ACTH and + AgII)
- Cholesterol converted to pregnenolone in mitochondria. Then modified to
either glucorticoid, mineralocorticoid or androgen.
Control
- Corticotropin-releasing factor (CRF) from the hypothalamus
stimulates ACTH secretion from the pituitary
- This in turn stimulates cortisol and androgen production by the adrenal cortex
Cortex
- Cortisol is produced by the zona fasciculata of the adrenal cortex
- Cortisol secretion is pulsatile every hour with a peak in the morning
- Levels are highest in the morning so replacement tries to mimic this
- Cortisol is excreted as urinary free cortisol and 17-oxogenic steroids.
- Adrenal hypofunction best stimulated with a short synthetic ACTH test
- Adrenal hyperfunction is best inhibited with Dexamethasone suppression test
Function
- Aldosterone is produced and released by the zona glomerulosa by the effect of the RAA system
- Cortisol is produced and released by the zona fasciculata by the effect of ACTH
- Androgens are produced and released by the zona reticularis by androgen stimulating hormone (still being determined)
Adrenal Medulla
- Adrenaline
- Noradrenaline
- Dopamine
Adrenal Receptors
- Alpha-1 (Agonist = phenylephrine)
- Vasoconstriction
- Relaxation of GI smooth muscle
- Salivary secretion
- Hepatic glycogenolysis
- Alpha-2 (Agonist = clonidine)
- Mainly presynaptic: inhibition of transmitter release (inc NA, Ach from autonomic nerves)
- Inhibits insulin
- Platelet aggregation
- Beta-1 (Agonist = dobutamine)
- Mainly located in the heart
- Increased heart rate + force
- Beta-2 (Agonist = salbutamol(Albuterol))
- Vasodilation and Bronchodilation
- Relaxation of GI smooth muscle