[Transient congenital hypothyroidism in iodine deficiency areas. Gruppo di Studio per il Registro Nazionale degli Ipotiroidei Congeniti].

On the basis of data collected in the National Register of infants with congenital hypothyroidism (CH), a mean incidence of 1 case of CH to 3200 live births has been estimated in Italy. Nevertheless a higher incidence (> 1:2000) than national mean value has been observed in several districts of our country. The aim of this study was to verify a possible occurrence of transient hypothyroidism (TH) in these areas. Results of our study showed that the proportion of infants with thyroid in situ was significantly higher in the areas with very high CH incidence than in the remaining parts of the country. Also serum TSH levels at confirmation showed a less severe hypothyroidism in infants of these areas when compared with the other CH infants. Furthermore, preliminary results of diagnosis reevaluation showed 58% of TH in the areas with CH incidence > 1:2000. Lower percentages of TH have been observed in the other areas in relation to the decreasing of CH incidence. Most of the high CH incidence areas are historically affected by iodine deficiency. This observation supports the hypothesis that iodine deficiency can contribute to the occurrence of transient disorders of thyroid function in our population and stresses the need of promoting diffusion of an adequate iodine prophylaxis.