Effect of menopause and estrogen substitutional therapy on magnesium metabolism.

Magnesium homeostasis was determined in 48 healthy premenopausal women and in 54 early postmenopausal women. After an initial examination, the 54 postmenopausal women were randomly allocated to two groups with 33 receiving placebo treatment and 21 receiving estrogen substitutional therapy for 2 years. The 24-hour mean urinary excretion rates of magnesium were increased in the 54 postmenopausal women compared with the premenopausal women, namely: 467 +/- 20 (SEM) versus 355 +/- 13 mmol/mol creatinine (p less than 0.001) or 33.9 +/- 1.2 versus 24.3 +/- 1.0 mumol/l glomerular filtration (p less than 0.001). The same pattern was observed when the excretion rates were determined on fasting 1-hour morning urinary collections. This postmenopausal hypermagnesiuria was reduced to the premenopausal level during 2 years of estrogen substitutional therapy (p less than 0.001). As no evidence of hypomagnesemia was found, postmenopausal hypermagnesiuria probably originates from increased intestinal magnesium absorption, somehow induced by estrogen deficiency.