Calculation of left ventricular volumes and systolic indices in monitoring the therapeutic effect of levothyroxine replacement therapy in subclinical hypothyroidism.

Background/aim: Subclinical hypothyroidism (SCH) is defined as high thyroid-stimulating hormone (TSH) and normal thyroxine (T4) levels. Data on the effects of early substitution with levothyroxine on psychophysical health in SCH are not consistent enough to support its general administration. The aim of this study was to examine the effect of 3-months levothyroxine (LT4) treatment on cardiovascular function in symptomatic SCH with TSH <10 mIU/L.

Methods: Anthropometric, biochemical, electro- and echocardiographic indices were measured in 35 patients with persistent symptomatic SCH (4 mIU/L < TSH <10 mIU/L; mean ± SD: 7.0 ± 2.1 mIU/L) and 40 healthy controls at baseline and three months after the euthyroid state had been achieved on LT4 for SCH group, or 3 months of follow-up for controls.

Results: The analyses showed a significant reduction in body weight (P = .030), systolic and diastolic blood pressure (P = .024, P = .019), TSH (P < .001) and thyroid peroxidase antibodies (TPO Ab) (P < .001) on LT4 in the SCH group. There was a statistically significant decrease in end-systolic (ESV) and end-diastolic volumes (EDV) (P < .001, P < .001, respectively) after LT4 treatment. LT4 therapy significantly increased values of ejection fraction (EF), global longitudinal, circumferential and radial strains (P < .001, P < .001, P < .001, respectively).

Conclusions: Our study confirmed an echocardiographic improvement of cardiac structure and function in treated individuals. Findings suggest the role of electrocardiographic and echocardiographic examination in objective monitoring for LT4 therapeutic effects.