Fig. 7.
Liver T4, T3, T1AM and H-T4, H-T3, and H-T1AM levels in euthyroid, hypothyroid, and hypothyroid mice with T4 or H-T4 replacement, as measured by LC-MS/MS. Inducing hypothyroidism for 2 wk decreases endogenous T4, T3, and T1AM. Replacement with T4 results in normal T4 and increased T3 with respect to euthyroid but no increase in T1AM with respect to hypothyroid. Replacement with H-T4 results in measurable H-T4 and H-T3, no increase in endogenous T4, T3 or T1AM, and no detectable H-T1AM. H-T4 and H-T3 were only detected in mice replaced with H-T4; n = 3 for euthyroid, hypothyroid, and H-T4 replaced; n = 2 for T4 replaced.