Hyperthyroidism, or hyperthyroidism, is characterized by a pentathlon, which is a measurement of free triiodothyronine (FT3), free thyroxine (FT4), as well as triiodothyronine (T3), thyroxine (T4), and thyroid-stimulating hormone (TSH), which provides feedback on the functional status of the thyroid gland. Patients with hyperthyroidism may have elevated serum T4, T3, FT4, and FT4. In the presence of severe concomitant disease, conversion of T4 to T3 is impaired, FT3 is normal and FT4 is increased (T4 thyrotoxicosis). Occasionally, patients have significant inconsistencies between T4 and T3, with normal T4 levels and elevated T3 levels alone (T3 thyrotoxicosis). It is recommended that patients with hyperthyroidism consult a doctor before having blood drawn, and follow the doctor’s instructions for full dosage and duration of medication on weekdays, rather than stopping or increasing or decreasing the dosage of medication privately, to avoid adverse effects.