Levothyroxine replacement therapy in patients with subclinical hypothyroidism and coronary artery disease

To assess the potential benefits and risks associated with levothyroxine (LT4) therapy in patients with subclinical hypothyroidism (SH) and concomitant coronary artery disease (CAD).

We enrolled 33 patients (4 male and 29 female subjects) with SH and CAD in this study. The study cohort consisted of 2 groups: 19 patients who were randomly assigned to receive LT4 therapy, titrated to maintain a normal serum thyrotropin level (main group), and 14 patients who did not receive any LT4 replacement therapy (control group). Variables of the lipid profile and left ventricular diastolic function were measured and 24-hour electrocardiographic monitoring was performed before randomization and at 6-month follow-up. Medical therapy for the CAD remained unchanged throughout the 6-month study period.

In the main group, no statistically significant differences were found in the lipids, variables of left ventricular diastolic function, and heart rate pattern between the hypothyroid and euthyroid states. Individual analysis revealed, however, that LT4 therapy was beneficial in terms of lipid abnormalities in those patients with lower body mass index, shorter history of CAD, and higher cholesterol levels at baseline. In the control group, we noted statistically significant prolongation of early filling deceleration time after 6 months, which indicated less flexibility of the left ventricular myocardium and diastolic myocardial dysfunction with long-term SH. In reference to adverse effects of LT4 therapy, 5 of the 19 patients had an increased rate of ventricular premature beats. These 5 patients were significantly older and initially had more supraventricular and ventricular premature beats than the rest of the main group. No ST depressions were recorded during LT4 therapy.

In patients with SH and CAD, LT4 therapy can be beneficial in diminishing lipid abnormalities in those with lower body mass index, briefer duration of CAD, and higher levels of cholesterol at baseline. Patients in our study who experienced adverse effects of LT4 treatment were older and had more supraventricular premature beats at baseline in comparison with the other patients.