EFFECT OF VITAMIN-D TREATMENT IN HYPOPARATHYROID PATIENTS - A STUDY ON CALCIUM, PHOSPHATE AND MAGNESIUM HOMEOSTASIS

Aim: This study was undertaken to examine the effects of long-term vit amin D treatment on calcium, phosphate and magnesium homeostasis at or gan level in hypoparathyroid patients, Methods: Fifteen vitamin D-trea ted hypoparathyroid patients were studied, eight of the patients in a combined Ca-47 kinetic and calcium, phosphate and magnesium balance st udy. Results were compared with a matched control group of 12 normal i ndividuals, Results: All the patients had normal serum levels of calci um, phosphate and magnesium, Absolute intestinal calcium absorption wa s increased (P < 0.0001). Urinary calcium excretion was normal, but ac tive tubular calcium reabsorption (TmCa/glomerular filtration rate) wa s low (P < 0.001). Bone resorption rates and bone mineralization rates were very low (P < 0.001 and P < 0.05). Twenty-four-hour urinary hydr oxyproline excretion and serum cross-linked carboxyterminal telopeptid e of type I were in the upper normal range. Serum alkaline phosphatase was normal, but serum carboxyterminal propeptide of human type I proc ollagen and serum osteocalcin were significantly reduced (P < 0.05). C alcium balance was positive and significantly different from controls (P < 0.001). All parameters from phosphate homeostasis were normal, In testinal magnesium absorption was low though not significantly differe nt from normal (P = 0.06). Urinary excretion of magnesium was not sign ificantly higher than normal, but renal magnesium reabsorption was red uced (P < 0.001). Magnesium balance was low, though the difference was not significant (P < 0.06). Conclusion: Long-term vitamin D treatment in hypoparathyroid patients resulted in a positive calcium balance. B one turnover was very low, Results of bone markers and resorption rate were conflicting. Vitamin D treatment apparently normalized the abnor malities previously found in phosphate homeostasis of hypoparathyroid patients. Magnesium homeostasis was disturbed, with a more negative ba lance compared with normal subjects, implying a state of magnesium def iciency in these patients.