Bone mineral density and body composition before and during treatment with gonadotropin-releasing hormone agonist in children with central precocious and early puberty
Major changes in bone mineral density (BMD) and body composition occur
during puberty. In the present longitudinal study, we evaluated BMD and
calculated volumetric BMD [bone mineral apparent density (BMAD)], bone
metabolism, and body composition of children (32 girls and 2 boys) with
central precocious and early puberty before and during treatment with GnRH
agonist (GnRH). Patients were studied at baseline and during treatment for
6 months (n = 34), 1 yr (n = 33), and 2 yr (n = 16). Lumbar spine and
total body BMD and body composition were measured with dual-energy x-ray
absorptiometry. The variables were compared with age- and sex-matched
reference values of the same population and expressed as SD score (SDS).
Bone age was assessed. Serum calcium, phosphate, alkaline phosphatase,
osteocalcin, the carboxyterminal propeptide of type I collagen (PICP),
cross-linked telopeptide of collagen I (ICTP), 1,25 dihydroxyvitamin D and
urinary hydroxyproline/creatinine, and calcium/ creatinine ratios were
measured. Mean lumbar spine BMD SDS was significantly higher than zero at
baseline (P < 0.02) and did not differ from normal, after 2 yr of
treatment. Mean spinal BMAD SDS and total body BMD SDS were not
significantly different from zero at baseline and had not changed
significantly after 2 yr of treatment. During therapy, fat mass and
percentage body fat SDS increased, whereas lean tissue mass SDS decreased.
Mean lumbar spine BMD and BMAD and total body BMD SDS, calculated for bone
age, were all lower than zero at baseline (BMD P < 0.001 and BMAD P <
0.05) and also after 2 yr treatment (respectively, P < 0.001, P < 0.05,
and P < 0.01). Biochemical bone parameters were significantly higher than
prepubertal values at baseline, and they decreased during treatment. In
conclusion, patients with central precocious and early puberty had normal
BMD for chronological age but low BMD for bone age, after 2 yr of
treatment with GnRH. Bone turnover decreased during treatment. Changes in
body composition resembled those seen in patients with GH deficiency