Thyroid function tests. Total T3, total T4, and TSH assays were performed on sera collected from adult males at between 12 and 17 weeks of age as described in Materials and Methods. Results are expressed as mean ± SD of wild type (n = 12), Tpst1−/− (n = 5), and Tpst2−/− (n = 5) samples. Statistical differences between groups were tested using a two-tailed Student’s t test with unequal sample variance. T3, T4, and TSH levels in wild type and Tpst1−/− mice are not statistically different. T3, T4, and TSH levels in Tpst2−/− mice are statistically different than wild type and Tpst1−/− mice. * p < 0.01, ** p < 0.001.