Hypothyroidism and subclinical hypothyroidism and their influence on autonomic cardiovascular regulation and metabolism

The aim of this review is to expose different opinions in the literature on the influence of TH and TSH on the autonomic vegetative regulation of cardiovascular function and metabolism in marked and subclinical hypothyroidism (sHT). Hypothyroidism causes changes in hemodynamics and in lipid metabolism, which are predisposing risk factors for cardiovascular diseases. Subclinical hypothyroidism proceeds asymptomatically but there are changes in the cardiovascular system and its regulation, as well as a possible need for hormonal treatment. Although according to literature sources the social and age groups studied are heterogeneous and different tests have been used to investigate the autonomic vegetative regulation, no single model for investigation and therapeutic behavior, especially in sHT, has yet been established. Heart rate variability (HRV) is determined by the balance of afferent sympathetic and parasympathetic influences on cardiac structures and can be used for risk stratification of cardiovascular complications in patients with hypothyroidism. Early detection of autonomic dysfunction and its treatment may improve the overall prognosis as well as the quality of life of patients with hypothyroidism and sHT and limit the rates of cardiovascular morbidity and mortality in these patients.