Serum phosphorus during the menstrual cycle.

In the continuing search for a simple, noninvasive, reliable method to detect ovulation, phosphorus (P) levels have been measured in women across a menstrual cycle. Salivary P has been reported to increase significantly in women periovulatory. Reports of serum P show no such periovulatory peak. We measured serum P in nine ovulatory and two anovulatory women during one menstrual cycle. Indirect indicators of ovulation were biphasic BBT curve and luteal phase serum progesterone more than 3 ng/ml. No significant periovulatory change in serum P was found, only small fluctations ranging from 0.99--2.76 mg/dl. The absence of a periovulatory serum phosphorus peak in this and other investigations of serum P suggests that if there is altered P metabolism during the menstrual cycle, it is not reflected in the serum. Other mechanisms, such as urinary or salivary excretion, may be operating to maintain serum P within the physiological range. This hypothesis needs to be explored.