Hypothyroidism and its rapid correction alter cardiac remodeling

PLoS One. 2014 Oct 15;9(10):e109753. doi: 10.1371/journal.pone.0109753. eCollection 2014.

Abstract

The cardiovascular effects of mild and overt thyroid disease include a vast array of pathological changes. As well, thyroid replacement therapy has been suggested for preserving cardiac function. However, the influence of thyroid hormones on cardiac remodeling has not been thoroughly investigated at the molecular and cellular levels. The purpose of this paper is to study the effect of hypothyroidism and thyroid replacement therapy on cardiac alterations. Thirty Wistar rats were divided into 2 groups: a control (n = 10) group and a group treated with 6-propyl-2-thiouracil (PTU) (n = 20) to induce hypothyroidism. Ten of the 20 rats in the PTU group were then treated with L-thyroxine to quickly re-establish euthyroidism. The serum levels of inflammatory markers, such as C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL6) and pro-fibrotic transforming growth factor beta 1 (TGF-β1), were significantly increased in hypothyroid rats; elevations in cardiac stress markers, brain natriuretic peptide (BNP) and cardiac troponin T (cTnT) were also noted. The expressions of cardiac remodeling genes were induced in hypothyroid rats in parallel with the development of fibrosis, and a decline in cardiac function with chamber dilation was measured by echocardiography. Rapidly reversing the hypothyroidism and restoring the euthyroid state improved cardiac function with a decrease in the levels of cardiac remodeling markers. However, this change further increased the levels of inflammatory and fibrotic markers in the plasma and heart and led to myocardial cellular infiltration. In conclusion, we showed that hypothyroidism is related to cardiac function decline, fibrosis and inflammation; most importantly, the rapid correction of hypothyroidism led to cardiac injuries. Our results might offer new insights for the management of hypothyroidism-induced heart disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Atrial Remodeling / drug effects
  • Atrial Remodeling / physiology*
  • Cytokines / blood
  • Fibrosis / blood
  • Fibrosis / drug therapy
  • Fibrosis / pathology
  • Heart / drug effects*
  • Hypothyroidism / blood
  • Hypothyroidism / chemically induced
  • Hypothyroidism / drug therapy*
  • Hypothyroidism / pathology*
  • Male
  • Myocardium / pathology*
  • Propylthiouracil
  • Rats
  • Rats, Wistar
  • Thyroxine / blood
  • Thyroxine / pharmacology*
  • Thyroxine / therapeutic use

Substances

  • Cytokines
  • Propylthiouracil
  • Thyroxine

Grants and funding

This work was funded and supported by the Research Council of the Saint Joseph University - Faculty of Medicine. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.