Modificări cardiovasculare în hipotiroidismul subclinic | [Cardiovascular modifications in subclinical hypothyroidism]

Abstract

Although subclinical hypothyroidism is frequently diagnosed, the decision to initiate a substitutive therapy with LT4 remains controversial. Because the cardiovascular system is considered a main target for the action of thyroid hormone, we investigated whether subclinical hypothyroidism induces cardiovascular abnormalities. Fifteen patients (mean age 48±11) were evaluated by Doppler-echocardiography and reevaluated after 6 months of LT4 substitutive therapy (mean dose 64μg daily). Fifteen subjects (matched for age, sex) served as controls. Mean plasma TSH was significantly higher in patients, whereas mean serum free T4 concentrations, although in normal range, were significantly lower. Echocardiogram exam showed no abnormalities of the left ventricular morphology and a slight reduction in the systolic function in the patient group. In contrast, Doppler-derived indices of diastolic function showed significant prolongation of the isovolumic relaxation time (89±11 vs. 80±10msec), increased a wave (61±12 vs 52±11). Thyroid hormone profile was normalized by 6 months of treatment, whereas no changes were observed in the LV morphology. These findings indicate that subclinical hypothyroidism affects diastolic function and that this abnormality may be reversed by LT4 therapy.