Abstract
Background: Thyroid problems are on the rise among Indians. Over 4.2 crores people in India are estimated to suffer from such disorders making it increasingly important for people to pay attention to this often overlooked health problem.

Aims and Objectives: The present study was undertaken to compare electrocardiogram (ECG) profile in newly diagnosed hypothyroid subjects and hypothyroid subjects who were already receiving treatment for >5 years and to find out if there was any improvement in these parameters with thyroxine supplementation therapy.

Materials and Methods: A cross-sectional case–control study was carried out among 90 adults (males and females) of the age group of >30 years. The participants divided into three equal groups of 30 subjects (28 females and 2 males) each belonging to the same socioeconomic status. Individual with diabetes, hypertension, cardiovascular, pulmonary, renal or liver diseases, pregnancy, and other endocrine disorders was excluded from the study. Statistically significant variation in three groups determined by one-way ANOVA test and multiple comparisons between Group I versus Group II, Group I versus Group III, and Group II versus Group III done by Tukey test.

Results: Significantly decreased heart rate was seen in Group II as compared with Group I. No significant difference was found in Group I and Group III. In Group III, heart rate was high as compared with Group II. Significant prolongation of P-R interval was found in Group II as compared to Group I. No statistically significant difference was found in Group I and Group III. Mean value of PR interval was decreased in Group III as compared to Group II. Low-voltage QRS complex was seen in 8 of 30 patients and T-wave inversion in 5 of 30 patients, whereas these changes were absent in Groups I and III. ECG changes were all normal in Group III as this group was already on thyroid replacement therapy. Studies done by Tajiri et al., Sureshbabu et al., and Tudoran et al. documented similar findings.

Conclusions: Substitution therapy with levothyroxine significantly improves ECG changes in hypothyroidism.

Key words: Heart Rate; PR interval; QRS Voltage and T-Wave Inversion