During the last decade, circadian and episodic fluctuations of the plasma levels of pituitary hormones have been demon~ trated in man. The interest in the time dependence of the pituitary secretions partially originates from their close functional relation with the neuroendocrine mechanisms pre- sumably responsible for the control of the circadian.rhyth- micity in man. High frequency blood sampling techniques and specific radio- immunoassays have allowed to describe in detail the varia- tions over the 24-h cycle of the hormonal concentrations in healthy individuals under basal conditions as...