Thioamides are also a class of drugs that are used to control thyrotoxicosis. 
Thioamides have been incorporated into peptides as isosteres for the amide bond. Peptide modifications are analogues of the native peptide, which can reveal the structure-activity relationship (SAR). Analogues of peptides can also be used as drugs with an improved oral bioavailability. 
Thioamides inhibit the enzyme thyroid peroxidase in the thyroid, reducing the synthesis of triiodothyronine (T) and thyroxine (T), thereby blocking uptake of iodotyrosines from the colloid. They also block iodine release from peripheral hormone. Maximum effects occur only after a month, since hormone depletion is caused by reduced synthesis, which is a slow process.