mineralocorticoids

what is the main mineralocorticoid secreted

aldosterone

where is aldosterone secreted from in the adrenal cortex (which layer)

zona glomerulosa (outer layer)

what is the main role of aldosterone

regulation of sodium, potassium and water balance

true or false: mineralocorticoids have glucocorticoid activity

true - mineralocorticoids can have some glucocorticoid activity (and vice versa)

what is the main action of aldosterone on the kidney

increases Na+ reabsorption and promotes K+ and H+ excretion

how does aldosterone affect water balance

increased Na+ reabsorption causes passive water reabsorption which increases blood volume

what is the net effect of aldosterone on blood pressure

increases blood pressure

which receptor mediates aldosterone action

cytosolic mineralocorticoid receptor

how does aldosterone-receptor complex act inside cell

binds to nuclear DNA to induce gene transcription

which transport proteins are upregulated by aldosterone

• Na+ channels

• Na+/K+ ATPase pumps

name a competitive aldosterone receptor antagonist

spironolactone

what is spironolactone mainly used for

as potassium-sparing diuretic in oedema and hypertension

true or false: ACTH is important in long term aldosterone control

false - not a major long term regulator

what is ACTH’s role in aldosterone secretion

tonic maintenance (continuous, in the background) of zona glomerulosa

what triggers renin release from kidney

• low renal blood pressure

• reduced blood volume

what enzyme converts angiotensinogen to angiotensin I

renin

what converts angiotensin I to angiotensin II

ACE

what is the effect of angiotensin II on aldosterone

directly stimulates aldosterone synthesis and release

name 2 other actions of angiotensin II

• vasoconstriction

• stimulation of thirst

what class of drugs inhibit ACE

ACE inhibitors

how does plasma sodium affect aldosterone release

large decrease in Na+ stimulate aldosterone release

how does plasma potassium affect aldosterone release

small increases in K+ strongly stimulate aldosterone release

what is hypoaldosteronism

deficiency of aldosterone secretion

what are common causes of hypoaldosteronism

• renal disease like diabetes mellitus

• AIDs

key symptoms of hypoaldosteronism

• increased Na+ and water loss

• hyperkalaemia

• hypotension

how is hypoaldosteronism treated

mineralocorticoid replacement therapy

name the condition caused by hyperaldosteronism

Conn’s syndrome

what causes primary hyperaldosteronism

• adrenal hyperplasia

• aldosterone-secreting adrenal adenoma

what are the main features of Conn’s syndrome

• hypertension

• low plasma K+

• metabolic alkalosis

• muscle weakness

what happens to plasma renin levels in Conn’s syndrome

low plasma renin levels

how is primary hyperaldosteronism treated

• surgery

• aldosterone antagonists (e.g. sprionolactone)

what causes secondary hyperaldosteronism

excess renin release → increases angiotensin II

name causes of secondary hyperaldosteronism

• renal artery stenosis

• malignant hypertension

• juxtaglomerular cell tumour

• diuretic therapy

• heart failure

• liver cirrhosis

how is secondary hyperaldosteronism treated

• treat underlying cause

• long term spironolactone therapy