Bone demineralization and impaired mineral metabolism in insulin-dependent diabetes mellitus. A possible role of magnesium deficiency.

Osteoporosis, a recognized complication of insulin-dependent diabetes mellitus (IDDM), may be related to this complex metabolic disorder; moreover, some data emphasize an altered vitamin D metabolism or parathyroid hormone secretion. Mineral homeostasis was studied in 29 children with IDDM (18 males, 11 females; 2.6-18.0 years). In 17 patients a stimulatory test (low-calcium diet) was performed for PTH and 1.25(OH)2D. Bone mineral content (BMC) and BMC/BW were lower in respect to our normal values; bone mineral loss was directly related to HbA1c levels and insulin requirements. A significant decrease of ionized calcium (p less than 0.001) and magnesium (p less than 0.001) was found; intact PTH values were in the low normal range but decreased for the ionized calcium values. 1.25(OH)2D levels were not significantly different from normal levels. 1.25(OH)2D and intact PTH did not rise during stimulatory test. The lack of 1.25(OH)2D and intact PTH increase after the stimulatory test may be due to the parathyroid gland's hyporesponsiveness related to hypomagnesemia which impaired PTH release and/or PTH action. Our data confirm an involvement of 1.25(OH)2D and PTH regulation in diabetic osteoporosis.