Elevated Plasma Levels Of Oxytocin In Women Taking Low‐Dose Oral Contraceptives: Identification Of The Plasma Oxytocin With High Performance Liquid Chromatography

Abstract

The aim of the present study was to investigate whether low-dose oral contraceptives affect oxytocin concentrations in plasma. Twenty women particapted in an open cross-over study. Six consecutive blood samples were drawn twice, with a 4-week interval, in the luteal phase of the menstrual cycle when the women were/were not taking oral contraceptives. Plasma levels of oxytocin were analysed with a radioimmunoassay specific for oxytocin. A significant increase in oxytocin concentrations was observed following ingestion of oral contraceptives (p < 0.02). Women with the highest oxytocin levels during a normal menstrual cycle increased their levels the most when on oral contraceptives. Analysis with high performance liquid chromatography demonstrated that immunoreactive oxytocin found in plasma, whether with or without oral contraceptives, co-eluted with synthetic oxytocin standard. An interesting possibility could be that the mental side effects and effects on glucose metabolism occurring after treatment with oral contraceptives might be related to elevated oxytocin levels, since metabolic and CNS effects of oxytocin are known.