Permanent vs transient congenital hypothyroidism: Assessment of predictive variables

Objective: To assess clinical variables, including early thyroid scintigraphy, in predicting the outcome (permanent vs transient) in term infants with congenital hypothyroidism (CH). Methods: In a retrospective study, 142 full-term infants with CH diagnosed between 2000 and 2012 were categorized into three groups: agenesis/ectopic thyroid and permanent CH; eutopic thyroid and permanent CH; and eutopic thyroid and transient CH. All underwent early thyroid scintigraphy and were under regular follow-up in our tertiary Pediatric Endocrine Institute. Results: Thyroid scan showed agenesis/ectopic thyroid in 58 (41%) and eutopic thyroid in 84 (59%) infants. Imaging findings were similar in eutopic-permanent and eutopic-transient groups. At initial evaluation, TSH levels were higher in the agenesis/ectopic group than in the eutopic-permanent and eutopic-transient groups (71.5 6 11.2 mIU/L vs 49.1 6 27.9 mIU/L and 42.5 6 29.1 mIU/L, respectively; P, 0.001). Higher L-T4 doses were required from the third month in the agenesis/ ectopic than in the eutopic-permanent group (P, 0.001) and from the sixth month in the eutopic-permanent than in the eutopic-transient group (P, 0.01). Initial TSH .63.5 mU/L (P, 0.001) and L-T4 dose .4.6 mg/kg/d at age .6 months (P, 0.001) were found to be predictors for an agenesis/ ectopic gland using receiver operating characteristic analysis, as was an L-T4 dose .2.2 mg/kg/d at age .6 months (P, 0.01) for permanent CH in patients with a eutopic gland. Conclusions: Although early thyroid scintigraphy is reliable in predicting permanent CH when detecting agenesis or ectopic gland, it cannot differentiate between permanent and transient CH in cases with a eutopic thyroid. Confirmatory TSH at diagnosis and the L-T4 dose through treatment may better distinguish between permanent and transient CH.