Normal bone density but altered geometry in girls with Turner syndrome

Data on bone density and stability in Turner syndrome (TS) are contradictory. A confounding factor for interpretation is short stature. The aim was to measure bone density, geometry and stability in girls with TS compared to idiopathic short stature (ISS).

From 1999 to 2008, 59 girls with TS (35 prepubertal) were evaluated by pQCT. Mean age was 8.9 in prepubertal and 17.3 years in adolescent girls. Mean height was -3.1 and -1.8 SDS in prepubertal treatment-free and in adolescent, formerly rhGH-treated girls. For comparison, 18 prepubertal ISS girls were studied (age 7.7 years; height -3.3 SDS). Examination of radius with pQCT (XCT 2000). Cortical (CD) and trabecular density (TD), total bone area (TBA), cortical area (CA), cortical thickness, muscle area and strength strain index (SSI) were determined and compared with height related references.

In prepubertal girls with TS, TD and CD were normal (0.55 and 0.90 SDS) and comparable to ISS (0.95 and 1.53 SDS). TBA was greater in girls with TS than in ISS (0.87 vs. -0.33 SDS) whereas CA was similar (1.48 vs. 1.43 SDS). The SSI was comparable (1.61 vs. 1.56 SDS). Adolescent girls with TS showed similar results with a TD of 0.48 SDS, a CD of -0.32, TBA of 1.99, a CA of -0.05 and an SSI of 0.88 SDS.

The observations are consistent with normal bone density and stability but altered bone geometry in prepubertal and substituted adolescent girls with TS. This peculiarity may reflect SHOX deficiency. We therefore think that timely and adequate estrogen substitution could prevent bone loss in TS.