Diuretic effect of oxytocin in a patient with reversed diurnal rhythm of water and electrolyte excretion.

A reversed diurnal excretory rhythm of water, creatinine and electrolytes was observed in a woman with fluid retention that first appeared following a head injury 21 years previously. Synthetic oxytocin injections were given on the premise that she had a selective deficiency of oxytocin with normal vasopressin production. This treatment produced a diuresis and restored a normal excretory rhythm of water, creatinine and electrolytes. Inulin and PAH clearance studies showed that oxytocin increased the daytime glomerular filtration rate. These results suggest the possibility that oxytocin has an additional non-obstetrical physiologic function, viz. the regulation of the normal diurnal rhythm of glomerular filtration rate.