LAUSR

CONTEXT Prognostic biomarkers for monitoring bone health in adolescents with 21-hydroxylase deficiency (21OHD) are needed. OBJECTIVES To assess associations between concentrations of baseline bone turnover markers (BTMs) including osteocalcin (OC) and type-I collagen C-terminal telopeptide (CTX) and changes in lumbar spine bone mineral density (LSBMD) in adolescents with classic 21OHD. DESIGNS AND PATIENTS A retro-prospective study of 33 adolescents with classic 21OHD who had baseline data for LSBMD, bone age (BA), and BTM concentrations. METHODS BTM concentrations were converted into z-scores according to BA. We measured LSBMD at the follow-up study visit and calculated the annual percentage change in LSBMD (%∆LSBMD). RESULTS At baseline, participants (55% female, 79% Tanner 5) had mean (±SD) age of 14.6±3.6 years, BA 16.7±2.9 years, and average glucocorticoid (GC) dose 17.3±5.6 mg/m2 /day of hydrocortisone equivalent. The mean follow-up duration was 14.4± 5.6 months. Median (Q1-Q3) %∆LSBMD was 3.6 (0-8.5) %/year. %∆LSBMD was similar among genders or 21OHD subtypes. Prednisolone vs. hydrocortisone replacement resulted in lower %∆LSBMD (p = 0.004). Participants with high vs. low tertile of CTX z-score had increased %∆LSBMD (p=0.014). %∆LSBMD correlated negatively with GC dose (p=0.01) and positively with CTX and OC z-scores (p<0.01). In regression analyses, only CTX z-score positively associated with %∆LSBMD (p=0.003), adjusting for sex, BA, body mass index, testosterone, 25-hydroxyvitamin D, and GC type and dose. CONCLUSIONS Higher GC dose and the use of prednisolone were associated with decreased LSBMD accrual in adolescents with 21OHD. CTX z-score independently associated with LSBMD accrual, suggesting its potential for prognostic bone biomarker. This article is protected by copyright. All rights reserved.