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.