SUN-435 Longitudinal Growth Patterns During the First Three Years Post-diagnosis of Classic Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency: OUTSPREAD Study

Abstract Disclosure: M. Kim: None. Y. Lee: None. S. Cho: None. J. moon: None. C. Kim: None. H. Lee: None. M. Ahn: None. H. Lim: None. J. Kim: None. M. Kim: None. J. Suh: None. C. Shin: None. C. Cheon: None. Y. Lee: None. Objective: We investigated the growth trajectory and influencing factors over a 3-year period after diagnosis of classic congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (21-OHD). Method: This study included 89 patients (46 boys and 43 girls; 77 salt-wasting and 12 simple-virilizing type) from the multicenter OUTSPREAD cohort, who were diagnosed within the first six months of life and had at least one year of growth follow-up. Birth history, anthropometric data, dosage of hydrocortisone, dosage of fludrocortisone, and whether NaCl supplementation was used were collected at diagnosis and at 1, 2, and 3 years after diagnosis. Results: At diagnosis, the median age was 14.6 days (interquartile range(IQR), 7.3-36.5), and 27 (30.3%) were diagnosed within 30 days. Sixty-five (73%) patients were diagnosed after the introduction of neonatal screening test (NST) in 2006, with a higher proportion of boys (60% vs. 40% in girls, p=0.019). Boys were more likely to be asymptomatic at diagnosis (50% vs. 9.3% in girls, p<0.001), and were predominantly diagnosed through NST (80.4% vs. 37.2% in girls, p<0.001). The median hydrocortisone dose at diagnosis was 24.9 (IQR 18.1-71.8) mg/m2/day, which decreased to physiologic range, reaching 15.1 (IQR 10.0-42.7) mg/m2/day at 1 year, 11.2 (IQR 7.7-29.7) mg/m2/day at 2 years, 9.9 (IQR 6.9-26.9) mg/m2/day at 3 years. Nearly 90% of patients received fludrocortisone throughout the study period, and 57% were on NaCl supplementation during the first year. Height z-score decreased from 1.04±2.5 to -0.75±0.98 over a 3-year period (p<0.001), with the largest decline in the first year. However, weight z-score remained stable. The weight-for-height z-score increased from -1.27±2.72 to -0.43±1.18 (p<0.001) over 3 years, with the most pronounced increase in the first year. At the third year after diagnosis, 8.8% were overweight and 12.3% were obese. A multivariate-adjusted regression model showed that height gain in the first year was significantly attenuated in patients with a higher height SDS at diagnosis (p <0.001) and in those receiving a high hydrocortisone dose (≥15 mg/m² at both diagnosis and 1 year vs. others, p= 0.046). Conclusion: In patients with classic 21-OHD, height z-score decreased and adiposity increased over the 3 years post-diagnosis. Given that the most substantial height attenuation occurred in the first year, with higher height SDS at diagnosis and high hydrocortisone dosage identified as significant contributing factors, careful adjustment of hydrocortisone dosing during this period is required. Presentation: Sunday, July 13, 2025