Question

Diabetes insipidus is the syndrome which results due to the

• A. Failure of neurohypophysial system to inhibit the excess release of ADH
• B. Failure of neurohypophysial system to produce or release ADH
• C. Inability of pituitary to produce oxytocin
• D. Inability of pituitary to release ACTH

Answer 1

The correct option is B Failure of neurohypophysial system to produce or release ADH

Posterior pituitary is the part of brain that extends down from hypothalamus; the posterior pituitary and infundibulum are together termed as neurohypophysis. Vasopressin (antidiuretic hormone; ADH) and oxytocin are produced by hypothalamus but stored and released in to blood stream via posterior pituitary. ADH targets nephrons in kidney to increase water reabsorption and thereby decreasing water content in urine. Inability of neurohypophysial system to produce ADH causes excess urine production with resultant ion loss from blood. This condition is known as diabetes insipidus (watery urine). This makes option A incorrect and option B correct. Option C is incorrect as oxytocin (OT) stimulates uterine muscle contraction during child birth and initiates release of milk by mammary gland. Option D is incorrect as adrenocorticotropic hormone (ACTH) is secreted by anterior pituitary gland and targets adrenal cortex to produce its hormones which are namely mineralocorticoids and the glucocorticoids. Correct answer is B.