The mineralocorticoid aldosterone, secreted by the zona glomerulosa of the adrenal cortex, mainly acts to:

1. Aldosterone is the mineralocorticoid from the zona glomerulosa of the adrenal cortex. 2. It helps reabsorb sodium ions from the renal tubules. 3. It also increases excretion of potassium ions, regulating electrolyte balance. 4. Glucose formation from glycogen is a glucocorticoid (cortisol) action, raising heart beat is an adrenaline action, and lymphocyte production is thymosin, so those are ruled out. 5. So aldosterone's defining role is sodium reabsorption with potassium excretion. 6. The other three options describe cortisol, adrenaline and thymosin, confirming aldosterone is distinct. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 16 Plant and Animal Hormones "Mineralocorticoids", p.244_