Evidence for a Sex-Specific Facilitatory Effect of Melatonin on Prolactin Secretion. Is Pineal-Prolactin Interaction Relevant to the Clinical Course of Breast Cancer?

In all mammals tested so far melatonin (MT), the main pineal hormone, is secreted according to a large-amplitude circadian rhythm. Its profile of secretion is characterized by a brisk surge during the period of darkness with the peak in the first hours after midnight and decline before dawn; during the day-light hours serum MT concentrations are persistently low (Preslock,1984).