ADH is a hormone with which of the following characteristics?

ADH is a hormone with which of the following characteristics?

• A. It is a peptide hormone made in the hypothalamus and stored in the posterior pituitary.
• B. It decreases water permeability of the collecting duct.
• C. It is produced by the adrenal cortex.
• D. It directly lowers blood osmolarity.

Answer: (A)

ADH’s defining feature is that it is a peptide hormone involved in regulating water balance, produced by neurons in the hypothalamus and stored in the posterior pituitary until release. When osmolarity rises, ADH is released and travels to the kidney, where it binds to V2 receptors on collecting duct cells, triggering a signaling cascade that inserts aquaporin-2 channels into the apical membrane. This increases water reabsorption, concentrates the urine, and helps restore normal osmolarity. That made description—peptide hormone made in the hypothalamus and stored in the posterior pituitary—the best match. The other statements don’t fit ADH: it actually increases, not decreases, water permeability of the collecting duct; it is not produced by the adrenal cortex; and while its action can influence blood osmolarity, its primary effect is to promote water reabsorption rather than directly lowering osmolarity.

ADH’s defining feature is that it is a peptide hormone involved in regulating water balance, produced by neurons in the hypothalamus and stored in the posterior pituitary until release. When osmolarity rises, ADH is released and travels to the kidney, where it binds to V2 receptors on collecting duct cells, triggering a signaling cascade that inserts aquaporin-2 channels into the apical membrane. This increases water reabsorption, concentrates the urine, and helps restore normal osmolarity. That made description—peptide hormone made in the hypothalamus and stored in the posterior pituitary—the best match.

The other statements don’t fit ADH: it actually increases, not decreases, water permeability of the collecting duct; it is not produced by the adrenal cortex; and while its action can influence blood osmolarity, its primary effect is to promote water reabsorption rather than directly lowering osmolarity.