# Evaluation and correlation of heart rate variability and ventricular repolarization parameters in an Indian pediatric clinical hypothyroid population: a prospective cohort study

## TL;DR

This study found that hypothyroid children have altered heart rhythms and autonomic function, which improve with thyroid treatment.

## Contribution

The study is one of the first to evaluate cardiac electrophysiology and autonomic function in Indian pediatric hypothyroid patients before and after treatment.

## Key findings

- Hypothyroid children had prolonged Tpe intervals and reduced parasympathetic modulation compared to healthy controls.
- Levothyroxine treatment improved HRV indices and normalized cardiac electrophysiological parameters.
- Early treatment of pediatric hypothyroidism is critical to prevent cardiovascular risks.

## Abstract

To compare ventricular repolarization and heart rate variability in hypothyroid and healthy children and to assess the effects of levothyroxine therapy on cardiac electrophysiological and autonomic parameters. This study investigated ventricular repolarization parameters and heart rate variability (HRV) in hypothyroid children (5–12 years) compared with age-matched healthy controls and patients before and after thyroxine treatment. This study included 64 participants divided into hypothyroid and healthy groups (32 each). Parameters such as the Tpe interval, QT interval, and HRV indices were measured via standard electrocardiographic and HRV analysis techniques. Thyroid hormone levels were measured. Post treatment measurements were also performed on hypothyroid children following 3 months of levothyroxine therapy. Hypothyroid children presented significantly prolonged Tpe intervals (58.07 ± 9.21 ms vs. 53.80 ± 8.89 ms, p = 0.039), reflecting increased heterogeneity in ventricular repolarization. HRV analysis revealed decreased parasympathetic modulation (e.g., lower RMSSD and pNN50 values) in hypothyroid participants. Posttreatment improvements in HRV indices and thyroid hormone levels correlated with normalization of cardiac electrophysiological parameters. This study highlights that even mild thyroid dysfunction in children can subtly disrupt cardiac electrical stability and autonomic balance which may increase the risk of arrhythmia in this population. Timely thyroxine therapy not only restores thyroid levels but also powerfully rebalances the electrical and autonomic balance of the heart. These findings reaffirm the critical need for early detection and proactive treatment of pediatric hypothyroidism to safeguard lifelong cardiovascular health.

The online version contains supplementary material available at 10.1038/s41598-026-36745-2.