Related Experiment Video
Updated: May 29, 2026

Benefits of Cardiac Resynchronization Therapy in an Asynchronous Heart Failure Model Induced by Left Bundle Branch Ablation and Rapid Pacing
Published on: December 11, 2017
Effect of cardiac resynchronization therapy on thyroid function
Umut Celikyurt1, Aysen Agacdiken, Bilal Geyik
1Department of Cardiology, Kocaeli University Medical Faculty, Kocaeli, Turkey. ycelikyurt@gmail.com
Background:
Heart failure patients frequently have thyroid function abnormalities. Cardiac resynchronization therapy (CRT) is a major treatment for patients with advanced chronic heart failure. We aimed to investigate the effects of CRT on thyroid functions.
Hypothesis:
CRT improves thyroid functions.
Methods:
Fifty-seven patients (42 male, 15 female; mean age 58 ± 13 y) undergoing CRT were included in the study. Serum levels of thyroid hormones and echocardiographic parameters were measured before and 6 months after CRT. A response to CRT was defined as a reverse remodeling detected by a relative increase of ≥15% in left ventricular ejection fraction.
Results:
The clinical status and functional capacity of the patients in the remodeling group were improved significantly. The mean New York Heart Association class was reduced from 3.2 ± 0.4 to 2.2 ± 0.4 (P<0.001). The free triiodothyronine (fT3) level increased from 2.67 pg/mL to 2.97 pg/mL in the reverse remodeling group (P = 0.005). The fT3/fT4 ratio increased from 1.81 to 2.34 (P = 0.006).
Conclusions:
CRT improves fT3 levels and fT3/fT4 ratio, which may play an important role in reverse remodeling.
Related Concept Videos
Hyperthyroidism II: Pathophysiology
Synthesis and Regulation of Thyroid Hormones
Upon reaching the thyroid gland, TSH stimulates the follicular cells' active uptake of iodide ions from the blood. The ions diffuse to the apical surface of the cells and are oxidized to iodine. The iodine is then...
Functions of Thyroid Hormones
TH is indispensable for the normal development and maturation of the skeletal, muscular, and nervous systems during fetal and childhood growth. It facilitates bone mineral turnover and regulates protein synthesis in developing tissues, contributing significantly to overall growth and...
Hyperthyroidism I: Introduction
Hypothyroidism II: Pathophysiology
Graves Disease II: Pathophysiology
