Female cycling hormones and their functions

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Our interest in this book is not so much the primary (reproductive) role of these hormones as the impact they have on brain function and non-reproductive behavior.    So what we really need to know first is how their concentrations vary as a function of the menstrual cycle.   The boundary of the menstrual cycle is defined, of course, by the menses.   About half way between the menses, at the time when the ovum is released (i.e., at ovulation), four of these hormones reach their peak.   These are estrogen, LH and FSH and testosterone.  Progesterone reaches its peak a few days before menstruation and drops back to baseline immediately before the menses.   Finally, FSH and testosterone have a high plateau before ovulation whereas estrogen has a high plateau after ovulation and LH is equally low before and after ovulation.    This is a complex set of variations which is hard to investigate in a complete way.  For example, it is extremely hard to tease out an effect which could be attributed to any one hormone.  Very few psychoendocrinological or neuroendocrinological studies have assayed the full extent of variation of all these hormones.   So in short,  the picture we get is usually piecemeal,  and more often than not limits itself to distinguishing the follicular phase from the luteal phase.      In addition,  not all modulations of gender-specific hormones are tonic (smooth changes).  For example,  the woman’s ovarian function is in fact controlled by a releasing factor (luliberin) which is secreted in a pulsating manner by the pituitary gland.  As an aside on luliberin,  I might add that yeast organisms,  which are among the most primitive sexual beings known to exist,  also use this molecule to reproduce.