Document Detail

Short-term overt hypothyroidism induces sympathovagal imbalance in thyroidectomized differentiated thyroid carcinoma patients.
MedLine Citation:
PMID:  19549249     Owner:  NLM     Status:  MEDLINE    
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.
Karen A Heemstra; Jacobus Burggraaf; Agatha A van der Klaauw; Johannes A Romijn; Johannes W A Smit; Eleonora P M Corssmit
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Publication Detail:
Type:  Journal Article     Date:  2009-06-22
Journal Detail:
Title:  Clinical endocrinology     Volume:  72     ISSN:  1365-2265     ISO Abbreviation:  Clin. Endocrinol. (Oxf)     Publication Date:  2010 Mar 
Date Detail:
Created Date:  2010-04-09     Completed Date:  2010-07-01     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0346653     Medline TA:  Clin Endocrinol (Oxf)     Country:  England    
Other Details:
Languages:  eng     Pagination:  417-21     Citation Subset:  IM    
Department of Endocrinology and Metabolic Diseases, Leiden University Medical Centre, Leiden, The Netherlands.
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MeSH Terms
Autonomic Nervous System / physiopathology*
Carcinoma / surgery
Case-Control Studies
Catecholamines / urine
Heart Rate
Hypothyroidism / drug therapy,  etiology,  physiopathology*
Middle Aged
Prospective Studies
Stress, Psychological / physiopathology
Thyroid Neoplasms / surgery
Thyroidectomy / adverse effects*
Thyroxine / therapeutic use
Reg. No./Substance:
0/Catecholamines; 7488-70-2/Thyroxine

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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