Short‐term overt hypothyroidism induces sympathovagal imbalance in thyroidectomized differentiated thyroid carcinoma patients
Open Access
- 10 February 2010
- journal article
- Published by Wiley in Clinical Endocrinology
- Vol. 72 (3), 417-421
- https://doi.org/10.1111/j.1365-2265.2009.03655.x
Abstract
Context Thyroid hormone impacts on the cardiovascular system. (Subclinical) hyperthyroidism results in sympathovagal imbalance due to decreased vagal tone. However, conflicting data have been reported on the effects of hypothyroidism on the activity of the autonomic nervous system (ANS). In hypothyroidism, both increased and decreased sympathetic activity and increased vagal tone have been found. Objective To study the effects of acute short‐term overt hypothyroidism and thyroxine replacement therapy on the ANS by measuring urinary excretion of catecholamines and heart rate variability (HRV). Design Prospective study. Setting University hospital. Patients We studied 11 patients, previously treated with thyroidectomy for differentiated thyroid carcinoma, during hypothyroidism caused by cessation of thyroxine substitution for 4 weeks and during thyroxine replacement therapy, and 21 matched healthy controls. Main outcome measures The activity of the ANS was assessed by measuring urinary excretion of catecholamines and HRV at rest and during a challenge of the ANS by a mental stress test. Results Urinary dopamine excretion was significantly lower during hypothyroidism. Although in the patients total variability was unchanged, HRV analysis showed a significantly lower low frequency/high frequency ratio, indicating sympathovagal imbalance with sympathetic withdrawal. The mental stress test in the patients resulted in a significant increase in heart rate to the extent of 16–18%. This response was not different between the hypothyroid state and during thyroxine replacement therapy suggesting that cardiovascular reflexes in these patients remain intact. Conclusion Acute short‐term overt hypothyroidism results in sympathovagal imbalance with sympathetic withdrawal, with preservation of the cardiovascular reflexes to (mental) stress.Keywords
This publication has 31 references indexed in Scilit:
- Altered cardiovascular vagal responses in nonelderly female patients with subclinical hyperthyroidism and no apparent cardiovascular diseaseClinical Endocrinology, 2007
- Changes in Autonomic Modulation to the Heart and Intracellular CatecholaminesHormone Research in Paediatrics, 2006
- Hyperthyroidism is characterized by both increased sympathetic and decreased vagal modulation of heart rate: evidence from spectral analysis of heart rate variabilityClinical Endocrinology, 2006
- Heart rate variability and turbulence in hyperthyroidism before, during, and after treatmentThe American Journal of Cardiology, 2004
- Plasma catecholamines, blood pressure responses and perceived stress during mental arithmetic stress in young menBlood Pressure, 2004
- Thyroid disease and its treatment: short-term and long-term cardiovascular consequencesCurrent Opinion in Pharmacology, 2001
- Power Spectral Analysis of Variations in Heart Rate in Patients with Hyperthyroidism of HypothyroidismHormone and Metabolic Research, 1998
- Power spectral analysis of heart rate in hyperthyroidismJournal of Clinical Endocrinology & Metabolism, 1996
- Cardiac effects of long term thyrotropin-suppressive therapy with levothyroxineJournal of Clinical Endocrinology & Metabolism, 1993
- Abnormal Left Ventricular Function in HyperthyroidismNew England Journal of Medicine, 1982