Mineralcorticoids Flashcards
What is the main endogenous mineralocorticoid?
aldosterone
What is the main action of aldosterone?
increase Na+ reabsorption by the distal tubules in the kidney
concomitant increase in excretion of K+ and H+
What is Conn’s syndrome?
primary hyperaldosteronism
excessive secretion of mineralocorticoids, causing marked sodium and water retention with increased extracellular fluid volume and sometimes hypokalaemia, alkalosis and hypertension
What condition is caused by a decreased secretion in mineralocorticoids?
Addison’s disease
What can occur to sodium and potassium levels in a patient with Addison’s?
decreased aldosterone secretion can lead to Na+ loss (aldosterone normally increases reuptake in the distal tubule)
decrease in excretion of potassium causing hyperkalaemia
What region of the adrenal cortex secretes aldosterone?
zona glomerulosa
What conditions (plasma ion levels) stimulate aldosterone release?
low Na+ or high plasma K+
What is the main clinical use of mineralocorticoids?
replacement therapy in patients with Addison’s disease
What is the most commonly used mineralocorticoid drug?
fludrocortisone
What tissues is the mineralocorticoid receptor restricted to?
kidney, transporting epithelia of the bladder and colon
glucocorticoid receptor is found in most cells
What is the result of aldosterone binding with its receptor in either the kidney or epithelia of bladder or colon?
initiates transcription and translation of specific proteins resulting in an increase in the number of Na+-K+-ATPase molecules in the basolateral membrane
What drug can be used to treat hyperaldosteronism? (also used as treatment for heart failure and oedema)
Spironolactone
What is the mechanism of action of spironolactone?
acts as a competitive inhibitor of aldosterone
competitive binding of aldosterone receptors in the distal convoluted tubule
What are the side effects of spironolactone?
gynaecomastia and impotence because it has a blocking effect on androgen and progesterone receptors
