Effect of vitamin D treatment in hypoparathyroid patients: a study on calcium, phosphate and magnesium homeostasis.
OBJECTIVE
This study was undertaken to examine the effects of long-term vitamin D treatment on calcium, phosphate and magnesium homeostasis at organ level in hypoparathyroid patients.


METHODS
Fifteen vitamin D-treated hypoparathyroid patients were studied, eight of the patients in a combined 47Ca kinetic and calcium, phosphate and magnesium balance study. Results were compared with a matched control group of 12 normal individuals.


RESULTS
All the patients had normal serum levels of calcium, phosphate and magnesium. Absolute intestinal calcium absorption was increased (P < 0.0001). Urinary calcium excretion was normal, but active tubular calcium reabsorption (TmCa/glomerular filtration rate) was 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 hydroxyproline excretion and serum cross-linked carboxyterminal telopeptide of type I were in the upper normal range. Serum alkaline phosphatase was normal, but serum carboxyterminal propeptide of human type I procollagen and serum osteocalcin were significantly reduced (P < 0.05). Calcium balance was positive and significantly different from controls (P < 0.001). All parameters from phosphate homeostasis were normal. Intestinal magnesium absorption was low though not significantly different from normal (P = 0.06). Urinary excretion of magnesium was not significantly higher than normal, but renal magnesium reabsorption was reduced (P <0.001). Magnesium balance was low, though the difference was not significant (P < 0.06).


CONCLUSIONS
Long-term vitamin D treatment in hypoparathyroid patients resulted in a positive calcium balance. Bone turnover was very low. Results of bone markers and resorption rate were conflicting. Vitamin D treatment apparently normalized the abnormalities previously found in phosphate homeostasis of hypoparathyroid patients. Magnesium homeostasis was disturbed, with a more negative balance compared with normal subjects, implying a state of magnesium deficiency in these patients.
Mortensen
L
L
Department of Endocrinology and Metabolism, Aarhus Amtssygehus, Denmark.
Hyldstrup
L
L
Charles
P
P
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D001862:Bone Resorption / Q000378:metabolism; D002113:Calcification, Physiologic / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D005260:Female; D006706:Homeostasis; D006801:Humans; D007011:Hypoparathyroidism / Q000188:drug therapy / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000378:metabolism*; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood / Q000494:pharmacology*
D015415:Biomarkers; D010281:Parathyroid Hormone; D010710:Phosphates; D014807:Vitamin D; C097949:1,25-dihydroxyvitamin D; D008274:Magnesium; D002118:Calcium