Skeletal muscle intracellular ionized magnesium measured by 31P-NMR spectroscopy across the menstrual cycle.

OBJECTIVE

The hormonal regulation of magnesium (Mg) metabolism is poorly understood. Preliminary evidence suggests that reproductive hormones may influence Mg concentrations in various tissues. The purpose of this study was to determine if Mg concentrations in blood and muscle are affected by the phase of the menstrual cycle.

METHODS

Magnesium measures were obtained from 16 women over the course of one complete menstrual cycle. The principal outcome measure was intracellular ionized Mg ([Mg++]i) in skeletal muscle as measured by 31P nuclear magnetic resonance spectroscopy. Three blood measures (serum, red blood cell, and mononuclear blood cell) of total Mg ([Mg]) were also obtained.

RESULTS

Mean Mg concentrations were stable across the menstrual cycle with no evidence of a menstrual cycle phase effect for any of the measures. Furthermore, skeletal muscle [Mg++]i was not correlated with any blood measure of [Mg].

CONCLUSION

These results suggest that physiologic fluctuations in reproductive hormones do not influence either blood [Mg] or skeletal muscle [Mg++]i in healthy, regularly cycling women.