Catch‐Up Growth in Children With Congenital Hypothyroidism on Thyroxine Therapy: A Retrospective Study

Background and Objective Despite advances in neonatal care, delayed diagnosis and treatment of congenital hypothyroidism (CH) remain prevalent in regions lacking universal screening. This retrospective study evaluated catch‐up growth patterns in 65 children with a delayed diagnosis of CH. Study children were stratified into four groups based on age at thyroxine initiation: Groups A (< 1 year), B (1–<3 years), C (3–<5 years), and D (5–10 years). Measurements Growth outcomes, in terms of serial height z scores, skeletal maturation, proportion achieving catch‐up growth, and time to catch‐up, were assessed at baseline and after 3 years of thyroxine. Results Within 3 years of treatment initiation, 64.6% (42/65) of children achieved complete catch‐up in linear growth, and 56.9% (37/65) attained optimum catch‐up. Among those treated before 1 year of age (Group A), 76% (19/25) achieved complete and optimum catch‐up over a median (IQR) duration of 22 [12–33] months. In children diagnosed after 1 year of age (Groups B–D combined), 57.5% (23/40) attained complete catch‐up, of whom 78.3% (18/23) achieved optimum growth, with time to catch‐up increasing progressively with later age at diagnosis (median range—25–34 months). The greatest change in height z ‐scores was observed in the first‐year post‐treatment across all groups, with a decline thereafter. Catch‐up in skeletal maturation was observed in 72.3% (47/65) of children and occurred earlier than catch‐up in linear growth. Conclusion Early thyroxine initiation in CH is critical for optimal linear and skeletal growth. Delayed diagnosis is associated with slower, suboptimal recovery and an increased risk of compromised final adult height.