Prediction of Transient or Permanent Congenital Hypothyroidism from Initial Thyroid Stimulating Hormone Levels.

OBJECTIVE: To identify factors that discriminate between transient and permanent congenital hypothyroidism. METHODS: Retrospective evaluation of 58 children with congenital hypothyroidism and eutopic thyroid gland. Gender, gestational age, birth weight, TSH and serum thyroxine levels at diagnosis and L-thyroxine dose at 12 and 24 months of age were analyzed. RESULTS: Median (IQR) initial TSH levels were 73.3 (276.5) µIU/mL in permanent hypothyroidism and 24.24 (52.7) µU/mL in transient hypothyroidism (P =0.0132). The optimum cut-off value of initial TSH to predict transient hypothyroidism was 90 µIU/mL. Mean (SD) L-thyroxine doses at 24 months of age were 2.64 (0.98) µg/kg/day in permanent hypothyroidism and 1.91 (0.65) µg/kg/day in transient hypothyroidism. Requirement of L-thyroxine dose at 24 months of ≤0.94 µg/kg/day had the highest sensitivity (100%) to predict transient hypothyroidism. CONCLUSIONS: L-thyroxine doses at 24 months can predict transient hypothyroidism in patients with eutopic thyroid gland earlier than at 36 months.