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Correlation of autonomic indices with thyroid status
Sujata Gautam1, O P Tandon, R Awashi
1Department of Physiology, University College of Medical Sciences, G.T.B. Hospital, Shahdra, Delhi.
Indian Journal of Physiology and Pharmacology
|July 17, 2004
Summary
Thyroid dysfunction in women impacts autonomic nervous system function, specifically parasympathetic activity. This study found decreased parasympathetic function with elevated thyroid hormones, though sympathetic activity remained unchanged.
Area of Science:
- Endocrinology
- Autonomic Neuroscience
- Cardiovascular Physiology
Background:
- Thyroid hormones significantly influence metabolic processes and can affect cardiovascular and autonomic functions.
- Autonomic dysfunction is a recognized complication in patients with thyroid disorders, but its specific mechanisms require further elucidation.
Purpose of the Study:
- To compare the autonomic nervous system status in female patients with hyperthyroidism and hypothyroidism against healthy controls.
- To investigate the correlation between thyroid hormone levels and specific autonomic function indices.
Main Methods:
- Autonomic function was assessed using the Valsalva maneuver, standing-to-lying (S/L) ratio, and 30:15 ratio for parasympathetic status.
- Sympathetic status was evaluated using galvanic skin response (GSR).
- Statistical analysis included Student's t-test and regression analysis between autonomic indices and thyroid hormone levels (T3, T4, TSH).
Main Results:
- While mean autonomic function values did not significantly differ between hypothyroid and hyperthyroid groups, a significant correlation (P<0.05) was observed between the S/L ratio and thyroid hormone levels.
- A negative correlation was found between the S/L ratio and log [T3]/[T4], indicating decreased parasympathetic activity with increased T3 and T4 levels.
- Galvanic skin response (GSR) measurements indicated that sympathetic activity was not significantly affected by thyroid status.
Conclusions:
- Thyroid dysfunction, particularly elevated T3 and T4 levels, is associated with reduced parasympathetic activity in female patients.
- Sympathetic nervous system activity appears to be unaffected by thyroid status in this patient cohort.
- These findings highlight the specific impact of thyroid hormones on parasympathetic regulation and support previous research linking thyroid status to autonomic imbalance.