ESPE Abstracts

Background: In recent years, different studies have shown an increasing trend in the prevalence of transient congenital hypothyroidism, varying from 20 to 89%.

Aims/Objectives: 1. To determine the prevalence of transient hypothyroidism (TCH) among children diagnosed with congenital hypothyroidism (CH) on newborn screening (NBS). 2. To identify the predictive factors for distinguishing between transient and permanent hypothyroidism.

Methods: A cohort study was conducted in the Paediatric Endocrinology Clinic at a tertiary care Centre in rural Kerala, South India. 58 children diagnosed with CH on NBS and on levothyroxine therapy were conveniently sampled. At the age of 36–48 months, levothyroxine was trialed-off for an aetiological work-up. Children with high TSH and low free T4/Total T4 were grouped as permanent CH (PCH). These children underwent a 99mTc scan and in the case of athyreosis, a neck ultrasound was done to confirm the diagnosis. Children with normal TSH and normal free T4/Total T4, for a minimum period of 6 months after discontinuation of levothyroxine, were grouped as transient CH (TCH). The predictive factors were identified using Robust Poisson regression analysis and ROC analysis was done to establish optimum cut-off value for these factors. All the data was interpreted using descriptive and inferential statistics on R software and SPSS version 21.0.

Results: Of the 58 CH patients, 31 (53.4%) were diagnosed with transient CH (TCH). The newborn screening TSH, TSH at re-evaluation, free T4 (FT4) at re-evaluation and, levothyroxine dose at 1 year, 2 years and 3 years were significant predictors of transient CH. The optimum cut-off of newborn screening TSH is 68 mIU/mL with a sensitivity of 74% and a specificity of about 80% and the optimum cut-off of FT4 at re-evaluation is 0.99 ng/dL with 96% sensitivity and specificity and for TSH at re-evaluation is 8.2 µIU/mL with 100% sensitivity and specificity. The optimal cut-off dose of levothyroxine of 3.0 μg/kg/day immediately before trial-off could predict TCH with 100% specificity and 90% sensitivity.

Conclusion: Re-evaluation of CH must be standard of care in low middle income countries at 3 years of age as there is a higher prevalence of TCH than that observed worldwide. Initial TSH, levothyroxine dose requirement, and serum TSH and FT4 levels at re-evaluation have a predictive role in CH.