title: Association of sympathovagal imbalance with cardiovascular risks in overt hypothyroidism.
abstract: BACKGROUND
  Cardiovascular morbidities have been reported in hypothyroidism.
  
  
  OBJECTIVE
  The objective of this study is to investigate the link of sympathovagal imbalance (SVI) to cardiovascular risks (CVRs) and the plausible mechanisms of CVR in hypothyroidism.
  
  
  METHODS
  Age-matched 104 females (50 controls, 54 hypothyroids) were recruited and their body mass index (BMI), cardiovascular parameters, autonomic function tests by spectral analysis of heart rate variability (HRV), heart rate response to standing, deep breathing and blood pressure response to isometric handgrip were studied. Thyroid profile, lipid profile, immunological and inflammatory markers were estimated and their association with low-frequency to the high-frequency ratio (LF-HF) of HRV, the marker of SVI was assessed by multivariate regression.
  
  
  RESULTS
  Increased diastolic pressure, decreased HRV, increased LF-HF, dyslipidemia and increased high-sensitive C-reactive protein (hsCRP) were observed in hypothyroid patients and all these parameters had significant correlation with LF-HF. BMI had no significant association with LF-HF. Atherogenic index (β 1.144, P = 0.001) and hsCRP (b 0.578, P = 0.009) had independent contribution to LF-HF. LF-HF could significantly predict hypertension status (odds ratio 2.05, confidence interval 1.110-5.352, P = 0.008) in hypothyroid subjects.
  
  
  CONCLUSIONS
  SVI due to sympathetic activation and vagal withdrawal occurs in hypothyroidism. Dyslipidemia and low-grade inflammation, but not obesity contribute to SVI and SVI contributes to cardiovascular risks.
authors.affiliation: Department of Physiology, Jawaharlal Institute of Post-Graduate Medical Education and Research, Puducherry, India.
authors.forename: Avupati Naga
authors.initials: AN
authors.lastname: Syamsunder
authors.forename: Gopal Krushna
authors.initials: GK
authors.lastname: Pal
authors.forename: Pravati
authors.initials: P
authors.lastname: Pal
authors.forename: Chandrakasan Sadishkumar
authors.initials: CS
authors.lastname: Kamalanathan
authors.forename: Subhash Chandra
authors.initials: SC
authors.lastname: Parija
authors.forename: Nivedita
authors.initials: N
authors.lastname: Nanda
keywords: Autonomic imbalance; Body mass index; Cardiovascular risks; Dyslipidemia; High-sensitive C-reactive protein; Hypothyroidism; Sympathovagal imbalance