[Study of the pathogenic mechanism of hypocalcemia in primary hypomagnesemia. Demonstration of a blockage of the mechanism of release of parathyroid hormone].

Parathyroid function and peripheral responsiveness to parathyroid hormone were studied during magnesium dependent hypocalcemia in a 5 years old boy with primary hypomagnesemia. The bone system and the kidneys were responsive to exogenous bovine parathyroid extracts as demonstrated by the normalisation of the calcemia and the increase of urinary cyclic AMP, phosphorus and hydroxyproline. Low levels of serum immunoreactive parathyroid hormone gave also clear indication of impaired parathyroid function. By contrast intravenous injection of magnesium sulfate induced an instantaneous and very sharp increase of serum immunoreactive parathyroid hormone as shown by levels well above the normal range one minute after the injection ; this was followed by a regular decrease of hormonal levels reaching the normal range one hour later. This finding clearly demonstrates that severe magnesium depletion induces impaired parathyroid hormone release in man.