Endocrinology: Pre-ovulatory oxytocin administration promotes the onset of the luteinizing hormone surge in human females

Luteinizing hormone (LH) secretion during the ovulatory cycle is believed to be predominantly regulated by gonadotrophin-releasing hormone. Investigations in animals have strongly suggested that oxytocin also participates in LH control and the physiological events controlling LH surge initiation. In the human female, however, there has been no evidence supporting oxytocin's involvement in the processes leading to ovulation. In this study the effect of a preovulatory infusion of oxytocin on the onset of the LH surge was investigated in women aged 20–35 years who had natural ovulatory menstrual cycles of lengths between 25–35 days. Vaginal ultrasound scanning monitored follicular growth during the late follicular phase. When a follicle >>14 mm in diameter was observed each woman was randomized into one of two groups. One group (n = 8) received an oxytocin infusion of 256 mlU/min for 2 h, the other group (n = 8) received normal saline. The women who were administered oxytocin at this late follicular stage had an earlier onset of the LH surge than those who had received saline (P < 0.01). The results indicate that oxytocin promotes the onset of the LH surge in humans.