Options of Replacement Therapy in Hypothyroidism

Before the middle of XX century treatment of hypothyroidism implied prescription to the patients animals’ thyroid extracts, containing both, thyroxine and triiodothyronine [Oppenheimer JH, 1995]. Those drugs, in which it was almost impossible to measure the dose of thyroid hormones precisely, could not adequately provide euthyroidism. Moreover, it was rather difficult to prescribe proper doses. Furthermore there weren’t any objective control parameter for dose adjustment like modern TSH-assays. Synthetic preparations of levothyroxine (L-T4) have been used since about 1958, and levotriiodothyronine (L-T3) since 1956 (figure 1).