A low specific gravity of urine is most likely a sign of impairment in which hormone?

• A. Oxytocin
• B. Vasopressin
• C. Insulin
• D. Glucagon

Answer: (B)

A low urine specific gravity means the urine is dilute, which points to a problem with water reabsorption in the kidneys controlled by antidiuretic hormone (vasopressin). Vasopressin acts on the kidney’s collecting ducts to promote water reabsorption, making urine more concentrated. If vasopressin signaling or release is impaired, the kidneys don’t reclaim water effectively, producing dilute urine with a low specific gravity. Oxytocin doesn’t regulate water balance, and insulin and glucagon govern glucose metabolism, not urine concentration.