Table of Contents Author Guidelines Submit a Manuscript
Cardiology Research and Practice
Volume 2011, Article ID 381865, 6 pages
http://dx.doi.org/10.4061/2011/381865
Clinical Study

Acute Experimental Hyperthyroidism Does Not Affect Basal and Volume-Induced Atrial Natriuretic Peptide Secretion in Healthy Subjects

1Department of Cardiology and the Heart Failure Clinic, University Hospital of Larissa, University of Thessaly School of Medicine, Larissa, Greece
2Nuclear Medicine Unit, Hellenic Airforce (HAF) and Veterans Administration (VA) General Hospital, Athens, Greece
3Department of Internal Medicine, Hellenic Airforce (HAF) and Veterans Administration (VA) General Hospital, Athens, Greece
4Department of Endocrinology and Metabolic Diseases, University Hospital of Larissa, University of Thessaly School of Medicine, 41110 Larissa, Greece

Received 30 September 2010; Accepted 27 October 2010

Academic Editor: Georgios Giannakoulas

Copyright © 2011 Gregory Giamouzis 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

Background. Excess circulating thyroid hormones are associated with increased cardiac atrial natriuretic peptide (ANP) secretion but the exact mechanisms involved have not been fully elucidated in vivo. Methods. To examine whether thyroid hormone regulation of ANP secretion is the result of a direct action on the myocardium and/or of an indirect action through alterations in the peripheral circulation, plasma ANP levels (baseline and volume expansion-induced) were evaluated in 14 healthy men, before and after triiodothyronine (T3) administration. Results. T3 administration was followed by a significant increase in serum T3 levels and a significant decrease in serum TSH levels, without significantly affecting ANP levels. Systemic vascular resistance, plasma rennin activity (PRA), and aldosterone (ALDO) levels, as well as indices of left atrial function, were not significantly altered, despite a significant increase in cardiac output. Plasma volume expansion, induced by a 1500 ml normal saline (NSal) infusion, both before and after T3 administration, was followed by a significant decrease in PRA and ALDO and a significant increase in plasma ANP levels, without significantly affecting the mean blood pressure (BP) and heart rate (HR) in each study period. The NSal-induced response, measured as the integrated area under the curve corrected for baseline values (-AUC), was not different after T3 administration for ANP, ALDO, PRA, HR, and mean BP. Conclusion. In vivo thyroid hormone-induced myocardial ANP secretion is the result of an indirect action mainly through hemodynamic changes that increase atrial stretch.