Endocrine Abstracts

Aim: Subclinical Hypothyroidism (SH) is associated with cardiovascular disorders which may include increased risk for atherosclerosis, endothelial dysfunction and myocardial dysfunction.To investigate the prevalence of left ventricular systolic and diastolic dysfunction in patients with subclinical hypothyroidism and the effect of L-thyroxin therapy on myocardial performance using conventional echocardiographic parameters.

Method: The study includes 95 patients (F/M:83/12, age: 40.91±10.07 years) with SH as judged by elevated serum thyroid-stimulating hormone (TSH) levels (>4.2 mlU/l) and FT3 and FT4 within the normal range and 44 healthy controls (F/M: 39/5, mean age 38.77±9.59 years). None of the participants had hypertension or BMI>25 kg/m². All patients and the control group underwent standart echocardiography and Doppler imaging. E/A ratio [early (E) and late (A) mitral peak velocities] and the interventricular septum thickness (IVST) were determined. 25 SH patients with E/A ratio<1 were diagnosed as myocardial diastolic dysfunction and received LT4 replacement therapy during 6 months in order to establish euthyroidism. The biochemical and echocardiographic measurements were repeted six months later.

Results: The E/A ratio was significantly different among SH and control group.At the baseline the SH patients showed significantly lower E (0.83±0.25 vs 0.99±0.17, P<0.0001), E/A ratio 1.18±0.33 vs 1.33±0.23, P<0.003) and IVST (0.98±0.12 vs 0.91±0.08, P=0.001). Left ventricular end systolic and diastolic diameters were comparable between the two groups (P=0.025 and P=0.494 respectively). After 6 months of follow-up with LT4 replacement therapy, 25 patients with SH had significantly higher E/A ratio (1.09±0.22 vs 0.75±0.23, P<0.0001) and reduced (1.05±0.14 vs 0.95±0.10, P<0.0001) IVTS measurements. With the comparison of all groups with Pearson test, TSH levels show a parallelism with IVST (r=0.194; P=0.031).

Conclusions: LT4 replacement therapy may reverse the impairment of left ventricular dysfunction and IVST observed in SH patients and should be advised to prevent the alteration of myocardial function.