Thyroid hormone substitution therapy rapidly enhances left-ventricular diastolic function in hypothyroid patients

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.

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 microg/day).

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).

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.