Although we detected no changes in serum concentrations of thyroid-stimulating hormone or free tri-iodothyronine , free tetra-iodothyronine decreased by 19 % ( 23 to 16 ) in the 50 g eprotirome group and 27 % ( 30 to 23 ) in the 100 g eprotirome group ( p < 0.0001 vs placebo for both groups ) .