Autonomic functions in hypothyroidism

Background: Hypothyroidism is a common endocrine disorder in the general population. Most of the cardiovascular and neurological manifestations of hypothyroidism are due to autonomic dysfunction. The American Academy of Neurology has recommended simple bedside autonomic function tests for the diagnosis and follow-up of autonomic functions. Recognition of autonomic dysfunction and treatment of hypothyroidism may improve cardiovascular outcomes. This study aims to assess autonomic dysfunction in hypothyroidism and correlate it with serum thyroid-stimulating hormone (TSH) levels. Materials and Methods: This cross-sectional study was conducted on 60 patients diagnosed with hypothyroidism for 12 months at a tertiary care center in Southern India. Patients with a Zulewski clinical score over 5 and fulfilling the selection criteria were included in the study after obtaining written informed consent. Details of history, treatment, examination, and thyroid function tests data were collected and bedside tests for autonomic functions were performed. Results: Ninety percent of individuals were female, and the average age of the included study population was 40.38 ± 11.78 years. Based on TSH and FT4 values, the patients were subgrouped into currently euthyroid and overt hypothyroid individuals. The majority of the individuals (81.67%) included in the study had autonomic dysfunction. Based on the autonomic dysfunction score, there was a significantly higher proportion of overt hypothyroid individuals (n = 18) with severe autonomic dysfunction compared to euthyroid individuals (n = 4). About 75% of the study individuals had sympathetic dysfunction and 66.7% of individuals had parasympathetic dysfunction. There was no statistically significant association between autonomic dysfunction and the duration of hypothyroidism. Conclusion: Autonomic dysfunction in hypothyroidism is common; sympathetic dysfunction was observed more as compared to parasympathetic dysfunction.