The Effects of Combination Treatment T4 and T3 on Diastolic Functions and Atrial Conduction Time in Women with Low T3: A short term Follow-up Study

Abstract Purpose To investigate the effects of combination thyroid replacement treatment on left atrial volume (LAV), diastolic functions, and atrial electromechanical delays in women with low triiodothyronine (T3) levels. Methods The study consisted of forty-seven female patients with primer hypothyroidism. The patients who had low T3 levels, despite using tetraiodothyronine (T4) treatment for a while with normal thyrotropin (TSH) and T4 levels with levothyroxine (LT4) treatment and started combination therapy were included in the study. Biochemical samples (TSH, free T4, free T3) were taken, and an echocardiographic assessment was performed for patients at first admission and after approximately six months of receiving T3 (12.5 mcg) treatment. Results There was a statistically significant reduction at left ventricle (LV) end-systolic diameter (27.69 ± 3.14, 27.13 ± 2.89, 0.035), left atrial (LA) maximum volume (14.73 ± 3.22, 13.94 ± 3.15, 0.009), LA minimum volume(7.84 ± 2.45, 6.84 ± 2.30, < 0.001), LA vertical diameter (44.08 ± 6.92, 34.60 ± 4.31, < 0.001), LA horizontal diameter (45.65 ± 6.88, 33.43 ± 4.51, < 0.001), LAVI (50.73 ± 18.62, 41.0 ± 13.02, < 0.001), total conduction time (103.69 ± 12.70, 79.82 ± 18.40, < 0.001) after T3 replacement (respectively pre-post treatment and p-value). Conclusion The results of the current study suggest that adding T3 to LT4 treatment may improve LAVI and atrial conduction times in patients with low T3. However, more research with larger patient groups is needed to better understand the effects of combined hypothyroidism treatment on cardiac functions.