Serum calcium, magnesium and inorganic phosphorous levels during various phases of menstrual cycle.

Serum Calcium (Ca), Magnesium (Mg) and Inorganic phosphorous (Pi) were investigated serially during menstrual, follicular, ovulatory and luteal phases of menstrual cycle in 25 healthy medical student volunteers. The result shows significant cyclic variations within physiological limits in all parameters. Ca level was highest during ovulation (P < 0.001) and lowest during luteal phase (P < 0.001) compared to other phases. Exactly opposite result was observed for Ca level. It is lowest during ovulation (P < 0.001) and highest during the luteal phase (P < 0.001). However, the highest level of Pi was seen during menstrual phase (P < 0.001) and lowest during the luteal phase (P < 0.001). These changes are probably brought about under the influence of cyclic variations of the ovarian hormones.