Introduction: Although there are several studies on the incidence of congenital hypothyroidism (CH), there are few data showing incidence and evolution of CH detected by the second newborn screening (NBS).
Objectives: To assess the incidence of CH in Lombardia region and the percentage of patients identified by the 2ndNBS. To describe the clinical features and evolution of CH patients detected by the 2ndNBS.
Methods: The 1stNBS (cut-off blood-TSH>10mU/L) was performed at 25 days in all neonates born in Lombardia region. The 2ndNBS (cut-off blood-TSH>5mU/L) was performed in selected cases (prematurity, weight<2000g, malformations/syndromes, admission in NICU, twins, steroid treatment, maternal thyroid disease, borderline 1stNBS and associated risk factors).
Clinical data at diagnosis and re-evalutation of patients detected by the 2ndNBS (period 2007-2014) and followed-up at a single tertiary centre for paediatric endocrinology were collected. At 23 years, patients with gland in situ (GIS) underwent re-evaluation and were classified as permanent CH (s-TSH>10mU/L), persistent hyperthyrotropinemia (HT) (s-TSH 510mU/L), and transient CH (s-TSH<5mU/L).
Results: In the period 2007-2014, 767,157 newborns were screened for CH. 842 patients identified by NBS (67.6% by the 1stNBS, 32.4% by the 2ndNBS) were diagnosed with CH and treated with levothyroxine. The incidence of CH confirmed at birth (permanent and transient CH) was 1:911. Among the patients detected by the 2ndNBS, 101 were followed-up at our clinical centre: 38.6% were preterm, 15.8% had additional malformations. At diagnosis, s-TSH was between 10.31-756.60 mU/L (median: 34.25mU/L), mean s-FT4 was 0.87±0.39 ng/dl. Thyroid ultrasound showed 5 babies with thyroid dysgenesis and 96 with GIS. At reevaluation, among the patients with GIS 14 showed permanent CH (14.6%), 29 persistent HT (30.2%), and 53 transient CH (55.2%). Genetic analysis performed in 23 patients with GIS showed genetic variants in genes associated with CH in 12 cases (DUOX2:9 cases, TSHR:2 cases, PAX8:1 case).
Conclusion: Between 2007 and 2014 the incidence of CH confirmed at birth in Lombardia region was 1:911. In the absence of the 2ndNBS the incidence would have been 1:1348. In our cohort, preterm infants were 38.6%, indicating that other risk factors can contribute to delayed TSH elevation. In addition, the frequency of malformations was higher than expected. Although the majority of patients identified by the 2ndNBS had transient CH and HT, the 2ndNBS allowed the identification of severe cases of CH, cases of thyroid dysgenesis, and cases of CH caused by genetic variants in genes associated with CH.
19 Sep 2019 - 21 Sep 2019