Left Ventricular Diastolic Dysfunction in Patients with Subclinical Hypothyroidism

Abstract

Although subclinical hypothyroidism is frequently diagnosed, the decision to institute a substitutive therapy with L-T4 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. Twenty-six patients (mean age, 36 +/- 12 yr) were evaluated by Doppler-echocardiography, whereas a subgroup of 10 patients, randomly selected, were reevaluated after 6 months of L-T4 substitutive therapy (mean dose, 68 microg daily). Thirty subjects (matched for age, sex, and body surface area) served as controls. Mean plasma TSH was significantly higher in patients (P < 0.001), whereas mean serum free T4 and free T3 concentrations, although in the normal range, were significantly lower (P < 0.001 and P < 0.005, respectively). Blood pressure and heart rate did not differ from control values. Echocardiogram examination showed no abnormalities of the left ventricular morphology and a slight, but not significant, 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 (94 +/- 13 vs. 84 +/- 8 msec; P < 0.001), increased A wave (55 +/- 13 vs. 48 +/- 9 cm/sec; P < 0.05), and reduced early diastolic mitral flow velocity/late diastolic mitral flow velocity ratio (1.4 +/- 0.3 vs. 1.7 +/- 0.3; P < 0.001). In the subgroup of 10 patients, thyroid hormone profile was normalized by 6 months of L-T4 substitutive therapy, whereas no changes were observed in the left ventricular morphology. Systolic function was significantly enhanced, as compared with pretreatment values (P < 0.01) but did not differ from control values. Also, systemic vascular resistance was significantly decreased by L-T4 replacement therapy. Assessment of diastolic function showed significant shortening of isovolumic relaxation time (77 +/- 15 vs. 91 +/- 8; P < 0.05), reduction of A wave (51 +/- 13 vs. 60 +/- 12; P < 0.01), and increase of early diastolic mitral flow velocity/late diastolic mitral flow velocity ratio (1.7 +/- 0.4 vs. 1.3 +/- 0.3; P < 0.001). These indices, however, were comparable with those of control subjects. These findings indicate that subclinical hypothyroidism affects diastolic function and that this abnormality may be reversed by L-T4 substitutive therapy.

Subclinical hypothyroidism in childhood

“…Some studies of adults with SH showed abnormalities of myocardial function, reversible with L-thyroxine therapy 58 59. A small study of 16 DS children with prolonged SH, showed no difference in myocardial function compared to age and body-surface area matched euthyroid DS controls 60…”

Diastolic dysfunction and diastolic heart failure: diagnostic, prognostic and therapeutic aspects

“…LV DD develops in several cardiac diseases [30] as well as in extra-cardiac pathologies involving the heart (accumulation diseases as amyloidosis, thyroid disorders, acromegaly and others) [31,32] and in myocardial ischemia due to coronary artery stenosis or even to isolated dysfunction of coronary microcirculation [33]. However, the main cause of DD is arterial hypertension [5-7].…”

Effects of Subclinical and Overt Primary Hypothyroidism on the Cardiac Function and their Reversibility under Treatment Using Tissue Doppler Echocardiography

“…There has been a large number of studies which used the conventional analysis method of the mitral Doppler flow (29,43), but also the tissue Doppler evaluation (38,42,44) for the investigation of the LV function at patients with overt and subclinic hypothyroidism. In our study, the diastolic function was affected in both groups as compared to the control group, which is consistent with the previous studies.…”