Negative Feed Back Regulation of Oestrogen & Vasodilatory Function of Progesterone Responsible for Preovulatory Gonadotropin Surge [LH Surge] - A Hypothesis
Journal Title: Journal of Medical Science And clinical Research - Year 2015, Vol 3, Issue 4
Abstract
At present there are many universal observations related to GnRH pulse & Gonadotropins surge in female. The explanation regarding the possible cause of preovulatory LH surge is not clear. An effort is made to explain this, with help of multiple experimental & human study observations as follows First peak of oestrogen occurring 24hrs prior to ovulation Inhibition of GnRH at Hypothalamus. FSH + LH [from gonadotropes of pituitary] Oestrogen [from Theca interna cells] Regain of GnRH secretory pulse after 15hrs. 3½ times increased secretion of gonadotropins as preovulatory surge . This surge has decreased ratio of LH : total gonadotropins In conclusion “preovulatory gonadotropins’ surge” is better word used than “preovulatory LH surge”. There is one gonadotropin surge with one pulse of GnRH with LH content of 67% in follicular, 57% in preovulatory & 90% in luteal phases. Increase in LH content in luteal phase is due to vasodilatory effect of progesterone causing better hypothalamo – hypophyseal portal circulation, providing better nutrition supply of aminoacids [AA] favouring conversion of FSH to LH. The subunit of FSH with addition of 3 AA. gets converted to LH i.e. 112 AA in FSH & 115 AA in LH. Inspite of removal of inhibitory effect of 2nd peak of oestrogen on GnRH, Gonadotropins’ surge does not occur. This may be due to generalized vasoconstriction caused by sudden withdrawal of progesterone, resulting in poor nutrition of secretory cells of hypothalamus & pituitary
Authors and Affiliations
Dr. Asha A. Dharwadkar
Keywords
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