Aldosterone

11β ,21 -dihydroxy-3 ,20- dioxopregn -4-en -18- al

H02AA01

White solid

Mineralocorticoids

Fixed

Template: Infobox chemical / molecular formula search available

Aldosterone is a natural steroid hormone that is formed from cholesterol and is one of the mineralocorticoids. Aldosterone is sometimes referred to as a thirst hormone because it is secreted in increased dehydration.

Education

From cholesterol progesterone is formed via the intermediate pregnenolone by oxidation at C3. By further hydroxylation at positions 21β, 18β and 11β 18- Hydroxycorticosteron is formed. In a subsequent oxidation of the hydroxy group at the C18 atom arises from the aldosterone.

Aldosterone in the zona glomerulosa - produced - the outermost layer of the adrenal cortex. The increases aldosterone secretion by a reduction of blood volume and blood pressure ( mediated by angiotensin II via AT1 receptors) and hyperkalemia ( excessive potassium concentration in the blood). The sodium concentration in the blood affects the aldosterone synthesis in opposite directions: the sodium in the blood increases, the biosynthesis is inhibited, the sodium drops, it is stimulated. ACTH stimulates aldosterone synthesis during atrial natriuretic peptide ( ANP) inhibits the secretion. The biosynthesis of mineralocorticoids is stimulated by substances even with beta- adrenergic effect and inhibited by dopamine.

Function and regulation

Verbindungstubuli and in the kidney collecting ducts aldosterone effected via activation of mineralocorticoid receptors (MR ) has an increased incorporation of sodium channels ( ENaC) and transporters (Na / K -ATPase ) in the plasma membrane to the interstitium. Characterized the transportation of the sodium through the epithelium is facilitated, which results in an increased water reabsorption result. At the same time leads to an increased excretion of potassium and ammonium ions and protons. Total aldosterone causes an increase in extracellular fluid volume, a decrease in potassium concentration, and an increase of the pH value in the blood.

Its effectiveness can be inhibited by aldosterone antagonists such as spironolactone, canrenoate and eplerenone.

The effectiveness of aldosterone on the mineral balance is about 1000 times higher than that of cortisol because cortisol is converted to the aldosteronsensitiven cells by 11- β - hydroxysteroid dehydrogenase type 2 to cortisone and the receptor can not activate it. The receptor affinity is the same.

Aldosterone is regulated by the renin -angiotensin -aldosterone system. Furthermore, the increase in potassium concentration can activate the synthesis of aldosterone.

A major role of aldosterone and the renin -angiotensin -aldosterone system is the regulation of blood pressure. In addition, aldosterone appears to be required in the management of life-threatening stress.

Pathophysiology

Short-term, occurring within minutes or hours effects of aldosterone serve the maintenance of fluid, electrolyte and acid - base balance ( milieu intérieur ) by increasing the reabsorption of sodium and increased excretion of potassium and protons (physiological effects).

Chronic, over days, weeks and months increased aldosterone levels, on the other hand have adverse effects. It comes to a potassium deficiency ( hypokalemia), an increase in pH ( alkalosis), high blood pressure and an increased formation of connective tissue (fibrosis) in the heart and kidneys, which can ultimately heart and lead to chronic renal failure ( pathophysiological effects).

Normal values

The normal value in the blood plasma is 20-150 ng / l The aldosterone is decreased in adrenocortical insufficiency and shock, which aldosterone is increased in stress, after surgery, with increased angiotensin II activity ( hyperaldosteronism ).

Diseases

The primary hyperaldosteronism ( Conn's syndrome ) is rare, a secondary hyperaldosteronism is found, however, more common in heart failure and liver cirrhosis. Adverse effects of aldosterone were also in acute myocardial infarction, nephrotic syndrome, refractory hypertension, chronic renal failure, especially in diabetic nephropathy, and described metabolic syndrome.

A lack of aldosterone, for example, in the context of autoimmune disease ( Addison's disease ), a congenital adrenal syndrome (AGS ), or occur in a tuberculosis of the adrenal glands.

Fludrocortisone

Fludrocortisone ( C21H29FO5, 380.45 g · mol -1, CAS 127-31-1, ATC H02AA02 ) is a derivative of aldosterone artificial mineralocorticoid, which can compensate as a drug aldosterone deficiency. The trade name is H. Astonin side effects at high doses are hypokalemia, metabolic alkalosis, water retention (edema) and blood pressure increase.