Evaluation of bone density in girls with precocious and early puberty during treatment with GnRH agonist.

Background: Major changes in bone status occur during puberty. Most longitudinal studies have shown no impairment in bone mineral density (BMD) in girls with precocious (PP) and early puberty (EP) during and after GnRH agonist therapy.

Methods: In the present study we evaluated BMD, bone strength (BS) and bone metabolism in 26 girls with PP and with EP before and during treatment with GnRH agonist. BMD was measured by dual energy X-ray absorptiometry and BS was measured using the quantitative high frequency ultrasound technique at baseline, after 6 and 12 months from onset of therapy. Variables were compared with age- and sex-matched values of the same population. Biochemical markers of bone turnover were measured at the same intervals.

Results: Mean lumbar spine (LS) and femoral neck (FN) BMD were significantly lower at baseline (LS: p < 0.0001, FN: p < 0.0017) compared with age-matched reference values. Bone strength was significantly lower at the radius (p < 0.0001) and normal at the tibia. A non-significant increase in BMD and a significant increase in BS were observed throughout the first year of therapy with GnRH agonist. Serum bone specific alkaline phosphatase measurements were normal at baseline and remained stable. Urinary deoxypyridinoline\creatinine measurements were significantly higher (p < 0.0001) at baseline and decreased significantly (p < 0.001) during treatment.

Conclusions: Girls with central idiopathic PP and EP have lower BMD and BS for chronological age and increased bone resorption markers. These parameters show a trend of normalization during the first year of therapy with GnRH agonist.