Physiological effects of thyroid hormones in the aspect of comorbidity and healthy longevity

Currently, non-infectious diseases, among which various disorders of the endocrine system play a decisive role, occupy one of the first positions in the structure of morbidity and mortality. Endocrine pathology worsens the course of other diseases and is a significant adverse factor in increasing mortality, including cardiovascular accidents. Thyroid pathology ranks second in the structure of endocrine diseases, and an increase in the incidence and prevalence of thyroid pathology in older age groups has been noted in recent decades. Thyroid hormones reduce the concentration of cholesterol, phospholipids and triglycerides in the plasma, while the amount of free fatty acids may increase. Conversely, decreased secretion of thyroid hormones dramatically increases the plasma concentration of cholesterol and phospholipids, and is almost always the cause of a sharp increase in fat deposition in the liver. In the presence of dyslipidemia and arterial hypertension, primary hypothyroidism can be considered as a risk factor for atherosclerosis and, accordingly, ischemic heart disease, especially in the elderly. In conditions of chronic iodine deficiency, a number of autoimmune factors may play a significant role in goiter development. Patients with endemic goiter reveal enzymatic defects in the synthesis of thyroid hormones, which further stimulates autoimmune aggression and degenerative changes in the thyroid gland, leading to a gradual decrease in the functional activity of the gland – hypothyroidism. Iodine deficiency and autoimmune diseases of the thyroid gland are often components of a continuum of comorbidity, which requires personalization of their treatment, taking into account the risks of mutual influences of various pathologies.