Borderline congenital hypothyroidism in the neonatal period.

One of the most important etiological factors causing prolonged jaundice in the neonatal period is congenital hypothyroidism. Some infants may have abnormal thyroid function test results rather than overt congenital hypothyroidism. Although serum TSH levels are accepted as diagnostic when >20 microIU/l, TSH values higher than 7 microIU/ml cause a hypometabolic condition. In this study, we evaluated infants who had prolonged jaundice for hypothyroidism. A hundred and ten infants suffering from prolonged jaundice were admitted to our clinic during the study period. Among them, 61 infants had normal thyroid function results. Six patients had overt primary hypothyroidism. TRH stimulation test was administered to the 43 patients with mildly elevated TSH levels of between 5 and 20 microIU/ml. Peak TSH values were above 35 microIU/ml in seven patients, and these were considered as having an exaggerated response (borderline hypothyroidism). During the neonatal period, prolonged jaundice is a valuable diagnostic clue for hypothyroidism. In addition, the TRH stimulation test can be a diagnostic tool in evaluating infants with mildly abnormal thyroid function test results.