Water relations of the ovarian cycle

This study reports the likely pattern of change in serum osmolality during the normal ovarian cycle, together with that which occurs during ovulation-induction by gonadotrophin. The variation in serum osmolality is attributed to the action of oestrogen on venous distensibility, and the effect of that response on the osmotic equilibrium between intra- and extravascular fluid. Although the action of gonadotrophin is mediated by the products of follicular theca and granulosa cells, the physiological response is ultimately affected by water. Both ovulation and menstruation may therefore depend on achieving a critical water content of follicular fluid and endometrial tissue.