Table of Contents
Journal of Hormones
Volume 2013, Article ID 813264, 5 pages
http://dx.doi.org/10.1155/2013/813264
Clinical Study

Autonomic Cardiovascular Control in Hyperthyroid Women during Sleep

1Department of Biomedical and Clinical Sciences, L. Sacco Hospital, University of Milan, Via GB Grassi 74, 20157 Milan, Italy
2Pneumology Division, L. Sacco Hospital, Via GB Grassi 74, 20157 Milan, Italy
3Endocrinology Unit, L. Sacco Hospital, Via GB Grassi 74, 20157 Milan, Italy

Received 10 August 2013; Accepted 24 October 2013

Academic Editor: Elisabetta Baldi

Copyright © 2013 Eleonora Tobaldini et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Hyperthyroidism is characterized by hyperadrenergic symptoms (i.e., tachycardia, anxiety, and increased metabolic state). Although hyperthyroid patients often complain about an impairment of sleep, no data are available on sleep characteristics and autonomic cardiovascular control during sleep in these patients. We aimed to assess sleep qualitative indices and autonomic cardiovascular regulation during sleep in hyperthyroidism (Hyperthyr) and after treatment. Six subjects with a first diagnosis of Graves’ disease or hyperfunctioning nodule underwent a complete polysomnographic study (PSG) at the time of diagnosis and after the treatment, when they became euthyroid (Euthyr). ECG and respiratory signals were extracted and samples of consecutive 250–300 beats were analyzed using linear spectral and nonlinear entropy analysis of heart rate variability (HRV), during the different sleep stages. Heart rate was decreased and total power increased in Euthyr compared to Hyperthyr, both during wake and sleep; no changes of the sympathovagal balance were observed. Entropy analysis showed that regularity index was reduced in Euthyr compared to Hyperthyr, suggesting changes in the complexity of the cardiovascular control. Periodic leg movements (PLM) were reduced in Euthyr compared to Hyperthyr. In conclusion, hyperthyroidism seems to be associated with an increased sleep fragmentation, due to PLM and an altered cardiac autonomic control.