Thyroid Hormone Substitution Therapy Rapidly Enhances Left-Ventricular Diastolic Function in Hypothyroid Patients

Abstract

Objective: Alterations in thyroid status may lead to changes in both systolic and diastolic function of the heart. Pulsed Doppler echocardiography is a reliable non-invasive means of assessing left-ventricular (LV) diastolic function. The aim of the present study was to evaluate LV diastolic function in patients with primary hypothyroidism receiving thyroxine therapy. Methods: Twelve patients (all females, mean age 47 ± 17, range 16–69 years) with primary hypothyroidism were studied by pulsed Doppler echocardiography. The first examination was made before the start of thyroxine substitution and the second at 37–68 (mean 53 ± 10) days after commencing thyroxine treatment (mean dose 136 ± 22 µg/day). Results: During thyroxine substitution therapy, the hypothyroid patients became clinically euthyroid and serum T4 increased from 51 ± 21 to 119 ± 24 nmol/l; TSH decreased from 50.4 ± 55.3 to 1.2 ± 1.5 mU/l. During therapy, heart rate increased from 61 ± 8 to 68 ± 10 (p = 0.05). The LV posterior wall (7.8 ± 1.0 mm) and interventricular septum thickness (8.0 ± 1.4 mm) were significantly greater in hypothyroid patients than in the control subjects (6.4 ± 1.0 mm, p = 0.007 and 6.8 ± 1.0 mm, p = 0.04, respectively). There was no significant change in LV dimensions and wall thickness during follow-up. E/A_max increased significantly during treatment (from 1.679 ± 0.432 to 1.947 ± 0.335, p = 0.006). The isovolumic relaxation time shortened significantly (from 88 ± 23 ms to 75 ± 24 ms, p = 0.005). Conclusions: The present study shows that LV diastolic function as assessed by pulsed Doppler echocardiography in hypothyroid patients is enhanced by thyroxine therapy during a rather short follow-up period.