Abnormal water turnover associated with hypothalamic obesity.

Experimental obesity produced in rats by stereotaxic lesions of the ventromedial hypothalamus (VMH) resulted in hyperphagia, polydipsia, polyuria, decreased urine osmolality, and enhanced excretion of total solute and urea. A 24-h water deprivation test revealed the inability of VMH-lesioned rats to increase urine antidiuretic hormone (ADH) excretion. Thus, destruction of the VMH area appears to be accompanied by impairment of ADH secretion, resulting in a diabetes insipidus syndrome that is partially masked by food restriction and improved by treatment with exogenous ADH.