RESUMO
OBJECTIVE: Congenital heart disease (CHD) is one of the common diseases of childhood, which is classified into non-cyanotic and cyanotic types. It can affect thyroid function and lead to disruptions in thyroid hormone secretion and hypofunction. This study aimed to evaluate thyroid function in patients younger than 2 years old with cyanotic and non-cyanotic CHD. MATERIALS AND METHODS: In our study, 101 patients (female/male: 50/51) were included. The thyroid-stimulating hormone and thyroid hormones such as thyroxine (T4) and triiodothyronine (T3) were measured using the electrochemiluminescence method, and thyroid peroxidase antibodies were measured by an enzyme-linked immunosorbent assay. Subclinical hypothyroidism referred to normal levels of T4, with elevated levels of thyroid-stimulating hormone in the serum. RESULTS: The frequency of subclinical hypothyroidism and hypothyroidism in patients with cyanotic CHD was estimated at 27.5% and 10%, respectively, and 1 patient had hyperthyroidism. The majority of cyanotic and non-cyanotic CHD cases were diagnosed with tetralogy of Fallot (30%) and patent ductus arteriosus (32.79%). There were no significant differences between cyanotic and non-cyanotic groups regarding T3, T4, free T3, free T4, and anti-thyroid peroxidase antibody levels (0.389, 0.142, 0.354, 0.248, and 0.333, respectively). CONCLUSION: Based on the present findings, subclinical hypothyroidism is a common finding in cyanotic CHD patients during childhood, which is associated with increased levels of oxygen saturation, severity of cyanosis, and age.