Congenital hypothyroidism (CH), thyroid hormone deficiency caused by dysfunction of the hypothalamic-pituitary-thyroid axis. It is one of the most common endocrine dysfunction of childhood. This study aims to evaluate clinical characteristics of newborns referred to Hacettepe University Pediatric Endocrinology Clinic via national newborn screening program from 01.01.2024 to 01.01.2025 due to an elevation in thyroid-stimulating hormone (TSH). Forty-nine newborns (M/F: 28/21) with elevated TSH were included. Median age at referral was 17 days (range 7–52 days), median TSH in screening was 17.4 mIU/mL (5–192.4). Confirmatory testing at the clinic revealed a median TSH 5.94 mIU/mL (1.3–192.4) and free T4 (fT4) 12.5 pmol/L (1.9–20.84). 19/49 had confirmatory results diagnostic for primary CH (median age 13 days, TSH 43.1 mIU/mL (10.1–192.4), fT4 10.6 pmol/L (1.9–17.3) and were started on Na-levothyroxine (median 12.5 mcg/kg) the same day. Central hypothyroidism was not detected. One infant had thyroid hypoplasia. 30/49’s confirmatory tests did not indicate primary CH (median TSH 4.3 mIU/mL (1.3–9.3), fT4 13.5 pmol/L (9.1–20.8). It was observed that newborns diagnosed with primary CH were referred earlier (p=0.06) and had significantly higher screening TSH (p=0.001). This study revealed through newborn screening program, early identification and treatment within the first two weeks of life was achieved. Higher TSH levels at screening and earlier referral may be indicators of primary CH. Confirmatory thyroid hormone test of these newborns should be interpreted with higher suspicion.

Keywords: newborn screening, congenital hypothyroidism, Na-levothyroxine, TSH, fT4