Abstract
Introduction: Resistance to thyroid hormone (RTH) is an autosomal disease characterized by pituitary and peripheral tissue insensitivity to thyroid hormone, exemplified by elevated serum total and free thyroxine (TT 4, FT 4) concentrations coincident with inappropriate levels of thyroid stimulating hormone (TSH). The most common clinical manifestation of RTH is attention deficit hyperactivity disorder, a behavioral disorder affecting 3%–5% of the school age population. Methods: Utilizing the New York State newborn screening hypothyroid program, an anonymous study was performed on 600 filter paper blood specimens exceeding the 99th percentile of TT 4 values in each day's assays. This upper first percentile of TT 4 specimens was assayed for TSH and FT 4 from the same newborn specimen; controls consisted of age-matched specimens with TT 4 values at the 50th percentile. Results: The population mean for TT 4 was expectedly elevated in the test group; while TSH and FT 4 values were similar in both groups. Fourteen specimens displayed both elevated FT 4 and elevated TT 4 levels. Seven of these 14 specimens demonstrated inappropriate TSH levels, suggestive of RTH. Discussion: This anonymous study suggests that it may be feasible to identify newborns presumptively positive for RTH from screening specimens. Identification would be based on elevated TT 4, elevated FT 4 and inappropriately normal or elevated TSH. Studies to identify mutations in PCR-amplified thyroid receptor DNA from these newborn specimens, as a means of determining whether they represent infants with RTH, are in progress.
Published Version
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