CLINICALLY RELEVANT INTERACTIONS BETWEEN HORMONES AND MAGNESIUM-METABOLISM - A REVIEW

Data obtained in volunteers point to diurnal variations in magnesium ( Mg) concentrations in plasma/serum, sweat, breast milk and urine with peak times in the morning and a nocturnal minimum. Since Mg may modula te calcium (Ca) and potassium (K) metabolism and since these cations h ave been related to the therapeutic action of lithium, these data may be relevant for psychiatric patients. Small increases in serum Mg duri ng winter and decreases during summer are probably complex in nature. Female sex hormones profoundly affect Mg metabolism. Plasma Mg decreas es during the follicular, and especially the ovulatory phase of the me nstrual cycle and increases during menses. Oestradiol/progesteron favo ur skeletal Mg uptake; accordingly serum Mg levels are lowered during homonal treatment (contraception, osteoporosis therapy) and in fertile women compared to age-matched males. There are close interrelations b etween Ca-regulating hormones and Mg metabolism. Short-term Mg deficie ncy may be associated with increased PTH and unaltered levels of 1,25- (OH)(2) vitamin D and serum Ca, or with decreased concentrations of PT H, 1,25-(OH)(2) vitamin D and serum Ca. Long-term Mg deficiency is fre quently combined with (Ca-resistent) hypomagnesemic hypocalcemia and d ecreased PTH levels. However in hypoparathyroid patients, Mg may resto re the calcemic response to vitamin D compounds independently of PTH. Since Mg is required for adenylate cyclase activity (parathyroid gland , kidney, bones) defective cAMP generation may be the common underlyin g mechanism. During Mg i.v. infusions, PTH secretion is depressed in M g-sufficient volunteers and increased in Mg-deficient subjects. Ln Mg- deficient volunteers basal and angiotensin II-stimulated aldosterone l evels were higher than in Mg-sufficient controls. On Mg i.v. infusions , plasma renin concentrations are increased after 60 minutes due to si multaneously released prostaglandins. After 3 hours, aldosterone level s were significantly decreased, perhaps mediated through Mg-induced in tracellular Ca mobilization. Overactivation of the renin-angiotensin-a ldosterone system in patients with heart failure was associated with p ronounced hypomagnesemia. High-dosed captopril has a moderate Mg-spari ng effect. These data point to the necessity more attention to interac tions between hormones and Mg metabolism in clinical medicine. -