Article Figures & Data
Figures
- Figure 2
Individual values of serum reverse T3 levels in normal, hypothyroid, and hyperthyroid people and in athyreotic patients who had been given 50 µg of levothyroxine (LT4) and 400 µg of LT4 daily.
- Figure 3
Thyroxine (T4) can shed 1 iodine atom to become the active thyroid hormone 3,5,3’-triiodothyronine (T3) in a reaction catalyzed by D1 and D2, or its inactive isomer 3,3’5’-triiodothyronine (reverse T3) in a reaction catalyzed by D3. In further reactions (not shown) both molecules successively lose more iodine atoms, eventually becoming T0.
Tables
Severity of illness TSH Total T3 Free T4 Reverse T3 Probable cause Mild No change Mildly decreased No change Mildly increased Mildly decreased D2, D1 Moderate No change or mildly decreased Decreased No change or mild increase or decrease Increased Decreased D2, D1, possibly mildly increased D3 Severe Decreased Markedly decreased Mildly decreased Mildly increased Decreased D2, D1, possibly mildly increased D3 Recovery Mildly increased Mildly decreased Mildly decreased Mildly increased Unknown D1 through D3 = iodothyronine deiodinases; T3, triiodothyronine; T4 = thyroxine; TSH = thyroid-stimulating hormone (thyrotropin).
Adapted from Salvatore D, Davies TF, Schlumberger M, Hay ID, Larsen PR. Thyroid physiology and diagnostic evaluation of patients with thyroid disorders. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA; Elsevier; 2016:334–368, copyright 2016, with permission from Elsevier.
