Endocrine Abstracts

Idiopathic infantile hypercalcemia (IIH) (OMIM 143880) is characterised by severe hypercalcemia, failure to thrive, vomiting, dehydration and nephrocalcinosis. Laboratory evaluation of infants affected with this condition reveals hypercalcemia, suppressed parathyroid hormone and hypercalciuria. Recently loss of function mutations in CYP24A1 gene have been found to cause IIH (New England Journal of Medicine 2011 365 410–21). Short-term treatment for this condition includes intravenous rehydration, furosemide, glucocorticoids, and pamidronate. Low-calcium diet is the mainstay for managing IIH until there is resolution of hypercalcemia with age.

The aim of this study was to determine if dietary calcium restriction during infancy and early childhood adversely affected bone mineral density (BMD) in patients with IIH, when they were between 5- and 15-year-old. Nine patients with IHH who were treated with dietary calcium restriction for a period ranging from 1.7 to 4 years were studied. BMD of L1–L4 was measured using the dual energy absorptiometry and data was expressed as bone mineral apparent density (BMAD; g/cm³). The lumbar spine (LS) BMAD values transformed to Z-scores using the normative data (ADC 2007 92(1) 53–59). A peripheral quantitative computed tomography was used to measure the total and trabecular volumetric bone density (vBMD (mg/mm³)) of the distal radial metaphysis, at 4% of the non-dominant forearm length. Distal radial (DR) total and trabecular vBMD values were transformed to Z-scores using the normative data (Osteoporosis International 2009 20(8) 1337–1346). A one sample t-test was used to determine if measured bone parameters were significantly different to zero.

The mean (S.D.) Z-score of BMAD (0.09 (0.97)), DR total vBMD (0.32 (0.87)) and DR trabecular vBMD (−0.04 (0.76)) were not significantly different from zero.

From these results, we conclude that dietary calcium restriction for management of IIH during infancy and early childhood does not appear to adversely affect the distal radial and spinal BMD, when the patients were between 5- and 15-year-old.