Which hormone's secretion is primarily regulated by plasma osmolality?

Which hormone's secretion is primarily regulated by plasma osmolality?

• A. Vasopressin
• B. Prolactin
• C. Growth hormone
• D. ACTH

Answer: (A)

Plasma osmolality is a key signal for maintaining body water balance. When the blood becomes more concentrated, osmoreceptors in the hypothalamus detect this change and trigger the release of vasopressin from the posterior pituitary. Vasopressin then acts on the kidneys to promote water reabsorption by increasing the insertion of aquaporin-2 channels in the collecting ducts, which concentrates the urine and reduces plasma osmolality toward normal. Other hormones listed are regulated by different physiological cues: prolactin mainly follows dopamine control and nursing status; growth hormone is driven by GHRH and somatostatin with influences from sleep, exercise, and nutrient status; ACTH is governed by CRH with cortisol feedback. They are not primarily governed by plasma osmolality, making vasopressin the hormone most closely tied to osmotic regulation.

Plasma osmolality is a key signal for maintaining body water balance. When the blood becomes more concentrated, osmoreceptors in the hypothalamus detect this change and trigger the release of vasopressin from the posterior pituitary. Vasopressin then acts on the kidneys to promote water reabsorption by increasing the insertion of aquaporin-2 channels in the collecting ducts, which concentrates the urine and reduces plasma osmolality toward normal.

Other hormones listed are regulated by different physiological cues: prolactin mainly follows dopamine control and nursing status; growth hormone is driven by GHRH and somatostatin with influences from sleep, exercise, and nutrient status; ACTH is governed by CRH with cortisol feedback. They are not primarily governed by plasma osmolality, making vasopressin the hormone most closely tied to osmotic regulation.