What are the implications of melatonin in the peritoneal fluid?

The Authors evidence the presence of melatonin (MT) in the peritoneal fluid (PF). They researched possible correlations between MT and other protein and steroid hormones in the PF and in the plasma. The only significant correlation found was a "negative" one between plasma MT and plasma E2. The Authors exclude an ovarian source for peritoneal fluid MT. They believe that MT may have a role in menstrual cycle regulation, directly modulating ovarian steroid production. To determine if MT has indeed such a role, they feel it important to study the possible presence of ovarian MT receptors.