Spontaneous, gonadotropin-releasing hormone-induced, and progesterone-inhibited pulsatile secretion of human chorionic gonadotropin in the first trimester placenta in vitro.

Using a multichannel superfusion apparatus, the secretion of human chorionic gonadotropin (hCG) was measured at 1-6 minute intervals in placental explants at 7-9 weeks of gestation. hCG was found to be secreted in distinct pulses (4-5 fold above baseline) every 11-23 minutes peak to peak. Addition of one minute pulses of GnRH analog significantly increased, whereas pulses of progesterone decreased, pulsatile hCG secretion.