Abstract
Heart rate variability (HRV) is a measure of the physiological variation of R-R intervals, reflecting the sympathovagal balance. In both overt and subclinical hyperthyroidism, a relative increase in sympathetic activity has been demonstrated, mainly due to a decrease in vagal activity. The modifications of HRV during orthostatism in normal subjects resemble those seen in hyperthyroidism. We have studied the response of 19 patients with overt hyperthyroidism and 12 with subclinical hyperthyroidism during orthostatism using HRV and compared the results to those of 32 healthy controls. In the three groups, the R-R intervals decreased in the same proportion after orthostatism. The low frequency power (LF)/[LF + high frequency power (HF)] ratio, which reflects the sympathetic tone, also increased in the same proportion in the three groups. However, the mechanisms of the modulation of the sympathovagal balance during orthostatism were different among the three groups. In controls, the relative increase of sympathetic tone after orthostatism was due principally to a decrease in vagal tone (reflected by decreased power in the HF band), while in overt hyperthyroidism, where the power in the HF band was already minimal in the lying position, there was a clear increase in the LF band power during orthostatism. The results were intermediate in the subclinical hyperthyroidism group, reflecting a continuum of effects of the thyroid hormone excess on the autonomic nervous system. Our study shows that despite an apparent normal cardiovascular adaptation to orthostatism in hyperthyroidism, the modulation of the autonomic nervous system is profoundly modified.
Similar content being viewed by others
References
Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Eur Heart J 1996, 17: 354–81.
Stys A, Stys T. Current clinical applications of heart rate variability. Clin Cardiol 1998, 21: 719–24.
Cacciatori V, Bellavere F, Pezzarossa A, et al. Power spectral analysis of heart rate in hyperthyroidism. J Clin Endocrinol Metab 1996, 81: 2828–35.
Inukai T, Takanashi K, Kobayashi H, et al. Power spectral analysis of variations in heart rate in patients with hyperthyroidism or hypothyroidism. Horm Metab Res 1998, 30: 531–35.
Burggraaf J, Tulen JHM, Lalezari S, et al. Sympathovagal imbalance in hyperthyroidism. Am J Physiol Endocrinol Metab 2001, 281: E190–5.
Petretta M, Bonaduce D, Spinelli L, et al. Cardiovascular haemodynamics and cardiac autonomic control in patients with subclinical and overt hyperthyroidism. Eur J Endocrinol 2001, 145: 691–6.
Sawin CT, Geller A, Wolf PA, et al. Low serum thyrotropin concentrations as a risk factor for atrial fibrillation in older persons. N Engl J Med 1994, 331: 1249–52.
Otzenberger H, Gronfier C, Simon C, et al. Dynamic heart rate variability: a tool for exploring sympathovagal balance continuously during sleep in men. Am J Physiol 1998, 275: H946–50.
Biondi B, Palmieri EA, Lombardi G, Fazio S. Effects of thyroid hormone on cardiac function: the relative importance of heart rate, loading conditions, and myocardial contractility in the regulation of cardiac performance in human hyperthyroidism. J Clin Endocrinol Metab 2002, 87: 968–74.
Valcavi R, Menozzi C, Roti E, et al. Sinus node function in hyperthyroid patients. J Clin Endocrinol Metab 1992, 75: 239–42.
Maciel BC, Gallo L, Marin Neto JA, et al. The role of the autonomic nervous system in the resting tachycardia of human hyperthyroidism. Clin Science 1987, 72: 239–44.
Maciel BC, Gallo L Jr, Marin Neto JA, Maciel LM, Martins LE. Autonomic control of heart rate during dynamic exercise in human hyperthyroidism. Clin Science 1988, 75: 209–15.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Goichot, B., Brandenberger, G., Vinzio, S. et al. Sympathovagal response to orthostatism in overt and in subclinical hyperthyroidism. J Endocrinol Invest 27, 348–352 (2004). https://doi.org/10.1007/BF03351060
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF03351060