Sympathovagal imbalance in thyroid dysfunctions in females: Correlation with thyroid profile, heart rate and blood pressure.
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Date
2009-07
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Abstract
The aim of the study was to investigate the role of spectral
analysis of heart rate variability (HRV) for assessing the type and degree
of sympathovagal imbalance (SVI) and their link to cardiovascular
morbidities in thyroid dysfunctions. Forty-five female subjects (15 control
subjects and freshly diagnosed untreated 15 hypothyroid and 15 hyperthyroid
patients) were recruited for the study. Thyroid profile, body mass index
(BMI), basal heart rate (BHR), blood pressure (BP) and spectral indices of
HRV (TP, LFnu, HFnu and LF-HF ratio, mean RR, SDNN and RMSSD)
were assessed in all the three groups. LF-HF ratio was correlated with
thyroid profile, BMI, BHR and BP. SVI was more prominent in hyperthyroid
(P<0.001) compared to hypothyroid (P<0.05) subjects. LF-HF ratio was
correlated with thyroid profile in both hypo and hyperthyroid subjects; but
correlation with BHR and BP was significant only in hyperthyroidism.
Though the SVI was found to be due to both vagal withdrawal and
sympathetic activation, especially in hyperthyroidism, contribution by vagal
inhibition was prominent. Vagal inhibition contributes significantly to SVI
in thyroid dysfunctions, especially in hyperthyroidism. As the present study
indicates poor cardiovascular health due to vagal inhibition in patients
suffering from thyroid dysfunctions, attempt should be made to improve
vagal tone especially in hyperthyroid subjects to attain a stable
sympathovagal and cardiovascular homeostasis.
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Keywords
hypothyroidism, hyperthyroidism, LF-HF ratio, sympathovagal imbalance, vagal tone
Citation
Karthik S, Pal G K, Nanda Nivedita, Hamide Abdoul, Bobby Zachariah, Amudharaj D, Pal Pravati. Sympathovagal imbalance in thyroid dysfunctions in females: Correlation with thyroid profile, heart rate and blood pressure. Indian Journal of Physiology and Pharmacology. 2009 Jul-Sept; 53(3): 243-252.