Bone mineral content in girls with precocious puberty treated with gonadotropin-releasing hormone analog

In order to evaluate the effects of gonadotropin-releasing hormone (GnRH) analogs on calcium metabolism, we studied 12 girls with central precocious puberty (CPP) who were treated with the GnRH agonist D-Trp6-GnRH every 28 days. The patients' mean age +/- SD was 5.9 +/- 2.1 years. The patients were studied before commencement and after 6 and 12 months of treatment. We also studied 12 age-matched healthy girls who served as controls. Bone mineral content was measured by dual-photon densitometry with 125I, in the distal third of the left radius. We evaluated the serum levels of calcium, phosphate, magnesium, parathyroid hormone, calcitonin, 25-hydroxy-vitamin D and the 24-h urinary excretion of calcium, phosphate and magnesium. All of these parameters were found to be normal before and during the treatment in both groups. At the beginning of the study, the patients with CPP had significantly higher bone mineral content than controls (0.51 +/- 0.12 g/cm2 vs. 0.39 +/- 0.09, p < 0.001); after 6 months contents were 0.42 +/- 0.11 vs. 0.41 +/- 0.05, p < 0.01; and after 12 months 0.44 +/- 0.11 vs. 0.44 +/- 0.05, NS, for treatment and control groups, respectively. This difference remained after 6 months of treatment, while after 12 months no significant difference between patients and controls was found. Our study shows that girls with CPP have an increased bone mineral content and that GnRH analogs modify bone density with a consequent reduction, it seems, that is not related to any of the calcium parameters studied.