Endocrine Abstracts

Congenital hypothyroidism is frequently associated with congenital cardiac malformations (CCM). Studies in knock-out mice showed that heart and great vessels organogenesis share some nuclear transcription factors with the embryonic thyroid, suggesting that thyroid defects may have a higher prevalence in children with CCM. The present study investigated thyroid function and morphology in 280 children (145 M/135 F, aged 0.3–12 years), affected by CCM (septal defects, ductus arteriosus, Fallot tetralogy, valvular stenosis). Patients with Down syndrome, recent administration of iodinated contrast agents or receiving amiodarone were excluded. Hypothyroidism was diagnosed in 35 children (12.5%): two were identified at neonatal screening, while the remaining 33, though normal at neonatal screening, showed high serum TSH with normal free hormones levels (fT4 0.9–1.8 ng/dl (nv 0.8–1.9); fT3 3.0–4.0 pg/ml (nv 1.5–4.1)) in absence of low T3 syndrome, consistent with mild or subclinical hypothyroidism. Increased TSH levels were confirmed six months later. No relationship between hypothyroidism and type of CCM as well as age were detected. FreeT4 levels were lower in hypothyroid children compared with 69 age and sex-matched euthyroid children with inter-atrial defects (1.37±0.22 vs 1.46±0.18 ng/ml, mean±S.D.; P=0.04). Thyroid autoimmunity was present in only 2 hypothyroid children (5.7%). Thyroid ultrasound revealed normal morphology and ecogenicity in all hypothyroid children except in one case with emiagenesia. The mean HSDS (height standard deviation score) was lower in hypothyroid than in euthyroid children (−0.23±1.3 vs 0.26±1.3; P=0.04). This difference was not related to the CCM severity, as it was confirmed when we compared 12 hypothyroid with 93 age and sex-matched euthyroid children with inter-atrial defects and ductus arteriosus (HSDS-0.68±0.2 vs 0.40±1.4; P=0.017). In conclusion, a mild hypothyroidism frequently occurs in children with CCM and is rarely related to thyroid autoimmunity or dysgenesia. Moreover, the subclinical hypothyroidism seems to be associated with a relative stature deficit.