Differentiating transient and permanent congenital hypothyroidism: predictive clues from Istanbul, Türkiye

Congenital hypothyroidism (CH) requires early diagnosis to prevent irreversible neurodevelopmental impairments. This study aimed to determine cutoff values for initial capillary thyroid-stimulating hormone (TSH), first venous TSH, and levothyroxine (LT4) dose at 6 months to differentiate between transient and permanent CH.

A retrospective analysis was conducted on 289 patients diagnosed with CH at the Pediatric Endocrinology Clinic of the University of Health Sciences, Umraniye Training and Research Hospital, from January 2014 to September 2021. Patients received treatment and were followed for at least 6 months after treatment discontinuation or remained under therapy. Patients were divided into two groups: permanent CH and transient CH. Initial capillary TSH, first venous TSH, and LT4 dose at 6 months were recorded, and cutoff values were determined using ROC analysis.

Of the 289 patients, 179 (62 %) had transient CH and 110 (38 %) had permanent CH. The permanent CH group had significantly higher levels of capillary TSH, first venous TSH, and LT4 dose at 6 months (p<0.001). The cutoff values for predicting transient CH were <23.1 mIU/L for capillary TSH, <64.5 mIU/L for first venous TSH, and <3.6 µg/kg/day for LT4 dose at 6 months, all statistically significant.

Initial capillary TSH, first venous TSH, and LT4 dose at 6 months are reliable predictors for distinguishing between transient and permanent CH. These cutoff values provide clinical guidance, especially for early treatment discontinuation in patients with LT4 doses below 3.6 µg/kg/day, indicating a higher likelihood of transient CH.