Replacement Therapy for Hypothyroidism: Purpose and Indication for Correction

Hypothyroidism syndrome remains the most common form of thyroid dysfunction, accompanied by a decrease in the level of thyroid hormones in the blood and a variety of clinical manifestations on the part of almost all organs and systems. The development of a synthetic levorotatory thyroxine isomer and the discovery of the peripheral conversion of thyroxine to active triiodothyronine made it possible to propose monotherapy with sodium levothyroxine as the gold standard for the treatment of hypothyroidism of any etiology. The main principle of treatment of hypothyroidism syndrome is the replacement of thyroid function with levothyroxine preparations. The goals of substitution therapy include relief of hypothyroidism symptoms, restoration of biochemical euthyroidism and prevention of overdose with the development of iatrogenic thyrotoxicosis. In most cases, patients require lifelong replacement therapy, and a number of physiological and pathological changes during their lifetime may affect the need for levothyroxine and its dose to maintain the target level of thyroid-stimulating hormone. When planning treatment, it is important to take into account the age and gender of the patient, the presence of concomitant pathology, medications taken, vital activity, regime and nature of work. The dose of levothyroxine is determined by the severity of hypothyroidism and the presence of residual functioning thyroid tissue, body weight, as well as the target level of thyroid-stimulating hormone. Indications for extraordinary control of thyroid-stimulating hormone levels and dose adjustment of levothyroxine are symptoms of hypothyroidism or thyrotoxicosis, pregnancy, menopause or the beginning / end of taking drugs containing estrogen, the appearance of diseases or taking drugs that affect the absorption or metabolism of levothyroxine, a change in the trade form of the drug, a significant weight change. The main conditions for successful treatment of hypothyroidism remain high adherence to treatment and regular monitoring of thyroid function.