Hypothyroidism: current state of the problem

The article presents the issues of epidemiology, classification, and clinic of hypothyroidism. The frequency of hypothyroidism increases significantly with age. The most common form is primary hypothyroidism, caused by a pathological process in the thyroid gland itself. Secondary hypothyroidism or tertiary hypothyroidism is caused by insufficient secretion of thyroid- stimulating hormone (TSH), or thyrotropin-releasing hormone. The article deals with the main causes of primary and secondary hypothyroidism. The most common cause of primary hypothyroidism is autoimmune thyroiditis, which can develop both separately and simultaneously with other autoimmune diseases, as part of polyglandular syndrome. Special attention should be paid to the change of thyroid status as a result of adverse side reactions when using a range of drugs. The questions about the mechanisms of thyroid insufficiency development as a result of unfavorable side reactions when using a number of drugs (lithium preparations, iodine-containing compounds, tyrosine kinase inhibitors, etc.) have been raised. Undiagnosed hypothyroidism is a risk factor for the progression of already existing cardiovascular diseases. The severity of clinical manifestations is determined by the severity of thyroid hormone deficiency. There are no significant clinical differences between the pronounced forms of primary and secondary hypothyroidism. Depending on the degree of lesion, secondary hypothyroidism may be complicated by other manifestations of hypothalamic-pituitary disorders, as well as the latter may include a decrease in the secretion of antidiuretic hormone at a certain stage of their development. Diagnostic difficulties are discussed, as hypothyroidism disrupts the functioning of most organs and systems of the body (musculoskeletal, cardiovascular, urinary, gastrointestinal, central and peripheral nervous systems) and can be masked by various diseases. The final diagnosis of hypothyroidism is clarified by a number of laboratory and instrumental studies. Substitution therapy with levothyroxine is used to treat hypothyroidism of any etiology.