You are treating a 37-year-old woman who complains of an extreme thirst. She gets the greatest relief from consuming large quantities of ice water or by sucking on ice cubes. She reports that she also has to frequently urinate. You suspect she may be suffering from diabetes mellitus but assay for urine glucose shows that it is not elevated. Indeed the patient's urine is quite dilute. A deficiency in which of the following hormones is the most likely cause of the symptoms in this woman?

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Quizplus · Accepted Answer

The symptoms of extreme thirst and frequent urination with dilute urine suggest diabetes insipidus, which is caused by a deficiency in vasopressin (antidiuretic hormone, ADH). The secretion of vasopressin is regulated in the hypothalamus by osmoreceptors, which sense water and Na+ concentration and stimulate increased vasopressin secretion when plasma osmolarity increases. The secreted vasopressin increases the reabsorption rate of water in kidney tubule cells, causing the excretion of urine that is concentrated in Na⁺ and thus yielding a net drop in osmolarity of body fluids. Vasopressin deficiency leads to production of large volumes of watery urine and to polydipsia. These symptoms are diagnostic of diabetes insipidus.

You Are Treating a 37-Year-Old Woman Who Complains of an Extreme