Which statement about antidiuretic hormone (ADH) is true?: (A) It is synthesized in the posterior pituitary gland, (B) It increases salt and water reabsorption in the collecting tubules and ducts, (C) It stimulates thirst, (D) It has opposite effects on urine and plasma osmolality
Answer is D. ADH increases the permeability of the collecting tubules and ducts to water, but not to sodium, which in turn increases water reabsorption and decreases water excretion. As a result, urine concentration increases and the retained water dilutes the plasma. ADH is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus and has no direct effect on the thirst center.