Bone and body composition by DXA in girls with precocious puberty, premature thelarche, and prepubertal controls

Abstract Context Lumbar spine bone mineral density (BMD) rises sharply during puberty; earlier onset, as in central precocious puberty (CPP), may accelerate skeletal maturation and modify bone accrual. Objective To assess bone and body composition in girls with CPP/early puberty (EP), premature thelarche (PT), and prepubertal controls (PC). Patients and methods We analyzed 184 girls aged 5-9 years with suspected CPP/EP (108 CPP/EP, 76 PT) and 47 PC. DXA assessed L1-L4 and total body less head (TBLH) BMD, bone mineral content (BMC), and body composition. Derived measures included bone mineral apparent density (BMAD), trabecular bone score (TBS), android–gynoid fat ratio (A/G), fat mass index (FMI), and fat-free mass index (FFMI). Results Group CPP/EP showed greater height, BMI SDS, bone age (BA), FM, lean mass, and FFMI than controls, with higher L1-L4 BMD (P < .001) and a trend for higher ΔBMD L1-L4–TBLH Z-score (P = .07); L1-L4 BMAD Z-scores were similar. Versus Group PT, Group CPP/EP had higher Δheight-target height SDS (P = .005), BA (P < .001), and lean mass (P = .03); Group PT had higher A/G (P = .02) and TBS (P = .03). Within Group PT, girls with pubarche had higher height, BMI SDS, BA, FMI, A/G (P = .02) and L1-L4 BMAD Z-scores (P = .01). Conclusion Both CPP/EP and PT showed higher fat and lean mass than controls, with PT marked by greater central adiposity. Only overweight/obesity, and pubarche onset in PT, were associated with increased L1-L4 BMAD Z-scores. DXA provides additional insight into body composition and bone accrual in girls with early pubertal signs.