Androgens have major influences on the regulation of bone mineralization. Because of their unique peripheral metabolism androgens may act on bone via activation of the androgen and/or estrogen receptor. Patients with complete androgen insensitivity syndrome (cAIS) are natural models to assess androgen actions on bone. We studied bone mineral density (BMD) in 10 patients with cAIS (mean age 13.70, range 4.7–19.8 years); 3 patients were studied before gonadectomy; the others were castrated and 6 were on hormonal replacement therapy. The BMD area (aBMD) was measured by dual energy X-ray; lumbar ‘apparent’ volumetric density (vBMD) was calculated using the formula vBMD = aBMD × [4/(π × width)]. In the patients, aBMD (0.72 ± 0.16 g/cm2) and vBMD (0.23 ± 0.04 g/cm3) were significantly (p < 0.001) reduced in comparison with those of a control group (n = 15, age 5.0–20.5 years: aBMD 1.028 ± 0.20 g/cm2; vBMD 0.35 ± 0.04 g/cm3). Both aBMD and vBMD were also reduced in comparison with normal values for males (aBMD –2.66 ± 0.99 SDS, p < 0.001; vBMD –3.08 ± 1.53 SDS, p < 0.0005) and females (aBMD –2.88 ± 1.05 SDS, p < 0.001; vBMD –2.84 ± 1.18 SDS, p < 0.0007). Real lumbar bone density, assessed by computed tomography in 1 patient, was also reduced (–6.2 SDS and –3.5 SDS for male and female normal values, respectively). Biochemical markers of bone metabolism were normal and not significantly different in patients and controls. Girls with cAIS did not have more fractures than controls. In conclusion, both aBMD and vBMD are reduced in cAIS patients, while bone turnover and the fracture risk seem not to be increased. Our data indicate that both androgens and estrogens may be required for acquisition of bone density during childhood.
Bone fibrous dysplasia is one of the main features of McCune-Albright syndrome, a rare genetic condition caused by constitutive activating mutations of Gs-protein and defined by skin dysplasia, bone fibrous dysplasia, and autonomous multiple endocrinopathies. Raised serum alkaline phosphatase (ALP) and urinary hydroxyproline levels indicating bone metabolic hyperactivity have been reported in these patients. Encouraging therapeutic results have been achieved, mainly in adults, with pamidronate, an aminobisphosphonate. In this study we investigate newer bone metabolic indices in a cohort of 11 children and adolescents treated with pamidronate. Tenfold increases of bone ALP and urinary pyridinoline cross-links were found and osteocalcin levels were twofold higher compared with reference values. After treatment, significant decreases in bone ALP and cross-links (Wilcoxon test P < 0.06) were found. Bone mineral density (BMD) significantly increased during treatment. There were signs of radiological healing as thickening of the cortical bone was found in some cases.
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