Responses to the administration of L-T₃ in a subject with RTHß harboring TRß G345R mutant and an unaffected individual. The hormone was given in three incremental doses, each for 3 days as illustrated in Figure 5. Results are shown at baseline and after each dose of L-T₃. (A) TSH responses to TRH stimulation. Note the reduced suppression of the TSH response by L-T₃ in the individual with RTHß. (B) Responses of peripheral tissues. Note the stimulation of ferritin and sex hormone binding globulin (SHBG) and the suppression of cholesterol and creatine kinase (CK) in the normal subject. Responses in the affected subject were blunted or paradoxical.