Predictive factors of permanent versus transient congenital hypothyroidism: a pragmatic cohort study

To identify clinical predictors of permanent congenital hypothyroidism (PCH) and transient congenital hypothyroidism (TCH).

This retrospective cohort study enrolled neonates with risk factors for congenital hypothyroidism as diagnosed by neonatal screening test or blood testing. Levothyroxine (LT4) dose and serum thyroid stimulating hormone (TSH) concentrations were recorded from birth to 3 years of age.

We enrolled 88 neonates, 35 with PCH and 53 with TCH. An LT4 dose > 3.8 μg/kg/day at 6 months (sensitivity 62%, specificity 96%), 3.0 μg/kg/day at 12 months (64%, 97%, respectively), 2.6 μg/kg/day at 2 years (80%, 98%), and 2.5 μg/kg/day at 3 years (89%, 98%) of age could predict PCH. Daily total LT4 doses > 50 µg at any time during the follow-up period were found solely in the PCH group (28% vs 0%, P<0.001). Independent discriminative predictors of PCH and TCH were TSH concentrations at diagnosis (beta=-4.3, P<0.001); daily LT4 dose at 6 (beta=-2.9, P=0.004), 12 (beta=-3.4, P=0.001), and 24 months of age (beta=-3.2, P=0.001); TSH > 5 μIU/mL at any time after treatment initiation (beta=-3.6, P<0.001); and increase in LT4 dose by more than twice (beta=-3.2, P<0.001).

Discrimination between PCH and TCH was achieved based on serum TSH concentrations at diagnosis, TSH > 5 μIU/mL during treatment, LT4 dose, LT4 > 50 µg during treatment, and increasing LT4 dose during treatment.