Progesterone has potent restraint on hypothalamus-pituitary-ovarian axis. It acts on unidentified hypothalamic pulse oscillator neurons. In turn, it acts on gonadotropins releasing hormone (GnRH) secreting neurons leading to inhibition of GnRH secretion. This results in inhibition of both luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion from anterior pituitary. The effect of progesterone appears to decrease GnRH pulse frequency which results in slowing down LH pulse frequency and reducing LH plasma concentrations
GnRH antagonist protocol is currently a good strategy for controlled ovarian stimulation in women with PCOS undergoing IVF/ICSI cycles. Finding a protocol that can be a better alternative will help in improving the success rate of IVF/ICSI cycles