ULUSAL YENİDOĞAN TARAMA PROGRAMI İLE KONJENİTAL HİPOTİROİDİ TANISI ALARAK İZLEMDE KALICI VE GEÇİCİ KONJENİTAL HİPOTİROİDİ TANIMLANAN OLGULARIN RETROSPEKTİF DEĞERLENDİRİLMESİ

Abstract

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder characterized by thyroid hormone deficiency. Newborn screening enables early diagnosis and treatment. Recently, lowering of screening cut-offs has increased the detection of permanent CH, however it also led to a substantial rise in transient cases, resulting in prolonged levothyroxine treatment until three years of age, when transient/permanent differentiation is typically established. This challenge is particularly pronounced in iodine-deficient populations. The present study aimed to identify clinical predictors that enable earlier differentiation between transient and permanent CH in patients diagnosed through newborn screening. We retrospectively analyzed the clinical, demographic, imaging, and laboratory characteristics of patients diagnosed with CH through the national newborn screening program between December 2006 and December 2024, who underwent transient/permanent differentiation at approximately three years of age. Patients with definitive permanent etiologies, such as thyroid agenesis or ectopy, were excluded; only patients with in situ thyroid gland were included. Odds ratios (OR) were calculated for potential predictors, and significant parameters in multiple logistic regression were further evaluated using receiver operating characteristic (ROC) analysis. Among the 244 patients included (106 females, 43.4%), 179 (73.4%) were classified as transient CH and 65 (26.6%) as permanent CH. The most powerful predictors of permanent CH were a levothyroxine dose >1.8 μg/kg/day (OR: 174.1; 95% CI: 12.2-2474.9; p<0.001), and a TSH level >3.3 mIU/L (OR: 172.2; 95% CI: 11.2-2652.5; p<0.001) at two years of age. Initial serum TSH level >72 mIU/L at diagnosis was also independently associated with permanent CH (OR: 7.15; 95% CI: 1.02-50.14; p=0.048). Levothyroxine dose and TSH levels at one year of age were also associated with permanent CH, albeit with lower effect sizes. Notably, all patients with a thyroid volume below -2 SDS on ultrasonography were classified as permanent CH. In conclusion, levothyroxine dose requirements and TSH levels during follow-up emerge as the strongest predictors for distinguishing permanent from transient CH in patients with a eutopic thyroid gland when there are no definitive structural abnormalities on imaging. This could potentially allow for earlier and more individualized treatment decisions to be made.