Human Prolactin: 24-Hour Pattern with Increased Release during Sleep

Abstract

Human prolactin was measured in plasma by radioimmunoassay at 20 minute intervals for a 24-hour period in each of six normal adults, whose sleep-wake cycles were monitored polygraphically. A marked diurnal variation in plasma concentrations was demonstrated, with highest values during sleep; periods of episodic release occurred throughout the 24 hours.