The Role of Thyrotropin-Releasing Hormone Stimulation Test in Management of Hyperthyrotropinemia in Infants

Objective: Hyperthyrotropinemia, which can be either a permanent or a transient state, is an asymptomatic condition and there is a controversy in management and long-term consequences. The aim of this study was to evaluate the results of thyrotropin-releasing hormone (TRH) test in infants with hyperthyrotropinemia.
Methods: Data of the patients who underwent a TRH test for mildly elevated thyroid-stimulating hormone (TSH) levels between 2004 and 2011 in a single academic pediatric endocrinology unit were retrospectively reviewed from the case files.
Results: Twenty infants (13 female, 7 male) with the median (range) age of 33 days (25-50) were enrolled into the study. The median basal TSH was 7.0 mIU/L (4.9-8.9) and free thyroxine level was 1.4 ng/mL (1.2-1.6) at the time of the TRH test. Thyroid ultrasonography was performed to 10 of the cases, and one of them had thyroid hypoplasia. TRH test revealed normal results in four infants, while sixteen infants had exaggerated response suggestive of primary hypothyroidism. The median follow-up period was 3.5 years (2.3-3.7). Therapy was discontinued in seven cases (2 had normal TRH response, 5 had exaggerated response) with the median age of 3.2 years (2.5-4). Of these seven infants, three had an elevated TSH on follow-up and L-thyroxine was restarted. All of the infants, in whom therapy was restarted, had exaggerated response to TRH.
Conclusion: TRH test response could be a useful diagnostic test to evaluate the persistence of the disease during the infantile age period.