Which hormone is secreted by the adrenal cortex due to increased potassium levels in the blood and released by decrease in blood volume?

Which hormone is secreted by the adrenal cortex due to increased potassium levels in the blood and released by decrease in blood volume?

• A. Aldosterone
• B. Renin
• C. Antidiuretic hormone
• D. Calcitonin

Answer: (A)

Aldosterone from the adrenal cortex is the hormone at play. It is released in response to two cues: high potassium levels in the blood and signals indicating low blood volume. When potassium is elevated, the adrenal cortex’s zona glomerulosa increases aldosterone secretion to boost potassium excretion in the distal nephron. At the same time, a drop in blood volume activates the renin-angiotensin-aldosterone system, with angiotensin II acting as a strong stimulus for aldosterone release. Once aldosterone binds its receptors in the kidney, it upregulates sodium reabsorption through epithelial sodium channels and Na+/K+ ATPases in the distal tubules and collecting ducts. Sodium reabsorption draws water back into the bloodstream, increasing blood volume and pressure, while potassium is pushed into the urine, correcting hyperkalemia. Other options don’t fit because they aren’t produced by the adrenal cortex or aren’t primarily responsive to potassium or acute changes in blood volume: renin is an enzyme from the kidney; antidiuretic hormone comes from the posterior pituitary and mainly responds to osmolality; calcitonin from the thyroid governs calcium homeostasis.

Aldosterone from the adrenal cortex is the hormone at play. It is released in response to two cues: high potassium levels in the blood and signals indicating low blood volume. When potassium is elevated, the adrenal cortex’s zona glomerulosa increases aldosterone secretion to boost potassium excretion in the distal nephron. At the same time, a drop in blood volume activates the renin-angiotensin-aldosterone system, with angiotensin II acting as a strong stimulus for aldosterone release.

Once aldosterone binds its receptors in the kidney, it upregulates sodium reabsorption through epithelial sodium channels and Na+/K+ ATPases in the distal tubules and collecting ducts. Sodium reabsorption draws water back into the bloodstream, increasing blood volume and pressure, while potassium is pushed into the urine, correcting hyperkalemia.

Other options don’t fit because they aren’t produced by the adrenal cortex or aren’t primarily responsive to potassium or acute changes in blood volume: renin is an enzyme from the kidney; antidiuretic hormone comes from the posterior pituitary and mainly responds to osmolality; calcitonin from the thyroid governs calcium homeostasis.