ESPE Abstracts

Background: Patients with Klinefelter syndrome (KS) have an increased risk for osteoporosis and fractures in adulthood. Data on bone mineralization in adolescence are limited, although it is a known at-risk period for vitamin D deficiency, low calcium intake and evolving hypogonadism.

Objective and hypotheses: To study the bone mineralization in KS adolescents and its relationship with vitamin D/calcium and gonadal status. KS adolescents with low calcium intake, lower 25-OH vitamin D levels and lower testosterone and/or higher LH levels were expected to have a lower BMD.

Method: Lumbar spine bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DXA) and trabecular BMD at the distal radius by quantitative peripheral computed tomography (pQCT) in 29 (25 pubertal) KS adolescents without testosterone or vitamin D supplementation, who were between 10.1 and 18.1 years (median 14.8 years) old. 25 OH vitamin D, LH and testosterone concentrations were analysed by commercial immuno-assays. Pubertal status was assessed by Tanner score and calcium intake by a simplified food frequency questionnaire.

Results: Mean (SD) z-scores of standing height, spinal areal BMD and forearm trabecular volumetric BMD were 0.82(0.85), −0.40(0.97) and −0.09(0.99). Respectively 5/29 and 4/21 KS patients had a lumbar spine BMD and a radius trabecular BMD score below – 1, but none had a score <−2. Respectively 15/29, 15/29 and 11/24 had a high (>10 mIU/l) LH status, a low (<20 μg/l) 25-OH vitamin D status and a low (<500 mg/day) calcium intake. Spinal BMD z-score correlated significantly with height SDS (ρ=0.66, P<0.005), but not with 25-OH vitamin D, testosterone, LH concentrations or calcium intake.

Conclusions: Spinal and radial bone mineralization is normal during adolescence in KS patients, irrespective of their vitamin D and genital status. BMD results in KS adolescents have to be related to their height and pubertal status.