The Relation of Thyroid Function and Ventricular Repolarization: Decreased Serum Thyrotropin Levels Are Associated with Short Rate-Adjusted QT Intervals

Abstract

The linkage of thyroid dysfunction with ventricular repolarization properties has not been investigated extensively, although alterations might be associated with an increased ventricular vulnerability. The objective of the study was to investigate whether there is an association between functional thyroid status and rate-adjusted QT intervals (QTc). The population-based Study of Health in Pomerania included 4310 subjects aged 20-79 yr. Data of 3610 subjects (1862 women and 1748 men) without branch bundle blocks or pacemaker were available for the present analyzes. QTc with respect to thyroid status. Short QTc was defined below the 25th percentile, and long QTc above the 75th percentile of the gender-specific distribution. TSH levels were positively associated with QTc independent from potential confounders in multivariable analyses (P for trend = 0.001). Subjects with decreased TSH levels had shorter QTc than those with normal TSH levels (426.4 +/- 8.2 vs. 430.2 +/- 8.2; P < 0.001). Adjusted odds ratios for short QTc in subjects with elevated, normal, and decreased TSH were 0.87 (95% confidence interval 0.58-1.31), 1.00 (reference), and 1.53 (95% confidence interval 1.16-2.03), respectively (P for trend = 0.008). TSH levels were positively related to QTc in a population-based sample. Subjects with decreased serum TSH levels had an increased risk for short QTc. Whether these findings are of clinical significance has to be investigated by further studies.