The high response of TSH to the TRH is the first sign that is described in the impaired of the thyroid function, which is present with normal levels of thyroidal hormones (TH) and that is defined as subclinic hypothyroidism (ScH). There are some controversies about their ethiopathogenic mechanism, their related clinical aspects, response limit values of TSH to TRH, evolution and therapeutic conduct to be adopted. In order to try to bring some answers to these questions it was evaluated the behavior of 33 infants (CA 01·1.5y) 9 males and 24 females, hyperresponsives to the TRH test (30' cut-off level: 35 μUI/ml). Those patients were treated with LT4 (mean dose: 3.10 μg/kg/daily) in a variable period until obtaining the minimal age of 2 years old. The therapeutical support was stopped in 18 of 33 patients (54%) in order to evaluate persistence of ScH.
Material and Method: The patients analyzed where term infants and normal birth weight in 94% of the cases. It was registered the mother's background of thyroid pathology. It was determined at the beginning and in the intratreatment controls the SSD of Height (H) and growth velocity(GV) (Tanner), the relationship weigh/height (WFH%), bone age (Grewlich and Pyle), ecography and/or thyroidal scintigram with Tc99. Serum level of T4, T3, free T4 were measured by standard RIA: TSH by IRMA, TSH-TRH test (0, 30, 60 and 90' post 7 μg/kg of TRH IV). TSH-TRAB by inhibition of the linkage of125 I-TSH, and TPOAb and TGAb by direct radio assay. Evaluation of thyroid function and anti thydoideal antibodies in the mothers were made in subgroup of patients. The results were evaluated through descriptive statistics and tests t for paired samples.
