Đụng kêu GnRH kích thích kinh tế là điều cần thiết cho gonadotropin tổng hợp, và tần số nhanh hơn, mạch mỗi giờ, có lợi cho tổng hợp tiết LH và, trong khi xung chậm hơn, một xung mỗi h 3-4, ủng hộ tiết FSH. Tác dụng của tần số xung GnRH được điều chế ở mức độ LHand FSH-gen, và tần số trực tiếp kích thích sự sao chép | Precursors of PCOS 109 and FSH occurs during ovulatory cycles 11 . A pulsatile GnRH stimulus is essential for gonadotropin synthesis and more rapid frequencies one pulse every hour favor LH synthesis and secretion whereas slower pulses one pulse every 3-4 h favor FSH secretion. The effects of GnRH pulse frequency are modulated at the level of the LH-P and FSH-P gene and frequency directly stimulates gene transcription 12 . In addition GnRH frequency modulates the complex gonadotrope mechanism whereby follistatin production increased by rapid pulses can inactivate intragonadotrope activin reducing FSH-P transcription and mRNA expression 13 . In women modulation of GnRH pulse frequency is effected predominantly by ovarian hormones with major regulation occurring during the luteal phase 14 . Progesterone from the corpus luteum acts to enhance hypothalamic opioid activity which in turn slows GnRH pulse secretion to one pulse every 3-4 h 15 . As noted above this favors FSH synthesis and constitutes an important part of the mechanisms favoring preferential FSH secretion in the late luteal phase which in turn stimulates the next wave of cyclic ovarian follicular maturation. In humans the maximum GnRH pulse frequency is approximately one pulse per hour a frequency that is initially achieved during pubertal maturation. In adult women during the follicular phase inhibition of the slow luteal GnRH frequency is gradually released 16 so that by the midcycle LH surge GnRH pulses occur approximately once per hour. Indeed one pulse per hour appears to be the intrinsic GnRH frequency in adult women and reduction of this frequency is predominately effected by luteal progesterone. Estradiol plays a permissive role in that it is required for expression of hypothalamic progesterone receptors 17 . In addition estradiol in concert with inhibin A from the corpus luteum acts to directly suppress gonadotrope FSH synthesis and release during the mid-luteal phase. Estradiol in the .
