Year: 2026 | Month: July | Volume: 16 | Issue: 7 | Pages: 176-185
DOI: https://doi.org/10.52403/ijhsr.20260718
Autonomic Function Profile in Untreated Primary Hypothyroidism: A Hospital-Based Case-Control Study
Garima Pandey1, Ashutosh Jain2
1,2Department of Physiology, Index Medical College, Indore, Madhya Pradesh, India.
Corresponding Author: Garima Pandey
ABSTRACT
Background: Hypothyroidism is a prevalent endocrine disorder with metabolic, cardiovascular and neuropsychological consequences. Its effect on autonomic regulation is clinically important because autonomic imbalance may contribute to bradycardia, impaired pressor responses, fatigue, exercise intolerance and poorer quality of life.
Objective: To compare autonomic function between untreated primary hypothyroid patients and age- and sex-matched euthyroid controls, and to examine the relationship of thyroid hormone status with autonomic, functional and quality-of-life outcomes.
Methods: A hospital-based observational analytical case-control study was conducted among 60 adults, including 30 newly diagnosed untreated primary hypothyroid patients and 30 apparently healthy euthyroid controls. Autonomic assessment included heart rate variability indices, deep breathing E:I ratio, Valsalva ratio, 30:15 ratio, cold pressor response and blood pressure response to standing. Fatigue Severity Scale, six-minute walk test and SF-36 physical and mental component scores were used to evaluate clinical impact.
Results: Groups were comparable for age and sex. Hypothyroid patients had higher BMI, lower resting heart rate, higher blood pressure, elevated TSH and lower Free T3 and Free T4. HRV indices were significantly reduced in cases, with higher LF/HF ratio. Cardiovagal tests and sympathetic reflex responses were significantly abnormal. Fatigue was higher, while six-minute walk distance and SF-36 scores were lower in cases. Higher TSH and lower Free T4 were significantly correlated with poorer autonomic and functional outcomes.
Conclusion: Untreated primary hypothyroidism is associated with mixed autonomic dysfunction involving cardiovagal impairment and altered sympathetic vascular reactivity. Autonomic testing may provide useful clinical information beyond routine thyroid biochemistry and may help identify patients needing functional follow-up.
Key words: Hypothyroidism; autonomic function test; heart rate variability; TSH; Free T4; Fatigue Severity Scale; six-minute walk test; SF-36; dysautonomia; case-control study.