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Related Concept Videos

Hyperthyroidism II: Pathophysiology01:27

Hyperthyroidism II: Pathophysiology

Hyperthyroidism is a hypermetabolic state caused by elevated levels of thyroid hormones, triiodothyronine (T3) and thyroxine (T4). It results from dysregulation at the thyroid, pituitary, or immune system level and affects multiple organ systems.PathophysiologyThe most common cause of hyperthyroidism is Graves’ disease, an autoimmune disorder in which antibodies, specifically thyroid-stimulating antibodies (TSAb), a subtype of TSH receptor antibodies (TRAb), bind to and activate TSH receptors...
Imbalances in Cardiac Output01:26

Imbalances in Cardiac Output

The heart's primary function is to pump blood throughout the body, maintaining a balance between blood sent out (cardiac output) and blood returning (venous return). If this balance is disrupted, it can result in congestive heart failure (CHF), a severe condition where the heart becomes an inefficient pump, leading to inadequate blood circulation.
CHF can occur due to the failure of either side of the heart. Left-side failure leads to pulmonary congestion—the right side continues to send blood...
Hyperthyroidism I: Introduction01:25

Hyperthyroidism I: Introduction

Hyperthyroidism is a type of thyrotoxicosis characterized by the thyroid gland's overproduction of the thyroid hormones triiodothyronine (T3) and thyroxine (T4). This hormone excess increases the basal metabolic rate and enhances sensitivity to catecholamines.DiagnosisDiagnosis is based on clinical features and biochemical testing. It typically shows suppressed thyroid-stimulating hormone (TSH) levels below 0.4 mIU/L, with elevated free T3 and/or T4. Additional tests, including thyroid...
Synthesis and Regulation of Thyroid Hormones01:20

Synthesis and Regulation of Thyroid Hormones

Low blood levels of the thyroid hormones — triiodothyronine (T3) and thyroxine (T4) — signal the hypothalamus to release the thyrotropin-releasing hormone (TRH). TRH then reaches the pituitary gland and stimulates the release of thyroid-stimulating hormone(TSH) into the bloodstream.
Upon reaching the thyroid gland, TSH stimulates the follicular cells' active uptake of iodide ions from the blood. The ions diffuse to the apical surface of the cells and are oxidized to iodine. The iodine is then...
Hypothyroidism II: Pathophysiology01:23

Hypothyroidism II: Pathophysiology

Hypothyroidism is a disorder characterized by insufficient production of thyroid hormones, which regulate metabolism, energy balance, and multiple organ systems.TypesHypothyroidism is classified based on the level of dysfunction. Primary hypothyroidism results from intrinsic thyroid gland dysfunction, causing reduced hormone production despite normal or increased stimulation. Secondary hypothyroidism arises from inadequate thyroid-stimulating hormone (TSH) secretion by the pituitary. Tertiary...
Functions of Thyroid Hormones01:18

Functions of Thyroid Hormones

The thyroid hormone (TH) plays a pivotal role in the intricate orchestration of physiological processes, exerting profound effects on development, metabolism, and homeostasis throughout different life stages.
TH is indispensable for the normal development and maturation of the skeletal, muscular, and nervous systems during fetal and childhood growth. It facilitates bone mineral turnover and regulates protein synthesis in developing tissues, contributing significantly to overall growth and...

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Related Experiment Video

Updated: Jun 19, 2026

Magnetic Adjustment of Afterload in Engineered Heart Tissues
09:40

Magnetic Adjustment of Afterload in Engineered Heart Tissues

Published on: May 5, 2020

Thyroid hormone and chronically unloaded hearts.

Kenta Ito1, Yutaka Kagaya, Hiroaki Shimokawa

  • 1Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan.

Vascular Pharmacology
|November 3, 2009
PubMed
Summary

Chronic cardiac unloading, seen in spaceflight and heart failure, impairs heart function. Thyroid hormone treatment can restore heart cell function in unloaded hearts, offering potential therapeutic benefits.

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Last Updated: Jun 19, 2026

Magnetic Adjustment of Afterload in Engineered Heart Tissues
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Tachycardia-Induced Cardiomyopathy As a Chronic Heart Failure Model in Swine
10:08

Tachycardia-Induced Cardiomyopathy As a Chronic Heart Failure Model in Swine

Published on: February 17, 2018

Area of Science:

  • Cardiovascular Physiology
  • Space Medicine
  • Regenerative Medicine

Background:

  • Prolonged spaceflight and left ventricular assist devices (LVADs) cause chronic mechanical unloading of the heart.
  • This cardiac unloading mirrors conditions in end-stage heart failure.
  • Understanding the effects of unloading is crucial for astronaut health and heart failure treatment.

Purpose of the Study:

  • To investigate the impact of chronic cardiac unloading on heart function using a rat heterotopic heart transplant model.
  • To explore the potential of thyroid hormone therapy to counteract the detrimental effects of cardiac unloading.

Main Methods:

  • Utilized a heterotopic heart transplantation model in rats to simulate chronic cardiac unloading.
  • Assessed time-dependent changes in Ca2+ handling and myocyte contractility.
  • Analyzed myosin heavy chain (MHC) isozyme shifts and Ca2+ cycling-related protein expression.
  • Evaluated the effects of thyroid hormone treatment on cardiac function and protein expression.

Main Results:

  • Chronic cardiac unloading led to progressive declines in Ca2+ handling and myocyte contractility.
  • These functional changes were linked to alterations in MHC isozymes and Ca2+ cycling proteins.
  • Thyroid hormone administration successfully restored Ca2+ cycling protein expression, Ca2+ handling, and myocyte contractility.

Conclusions:

  • Chronic cardiac unloading induces significant functional and molecular changes in the heart.
  • Thyroid hormone therapy demonstrates efficacy in reversing these negative effects.
  • Findings suggest potential clinical applications for thyroid hormone in managing cardiac unloading in spaceflight and heart failure patients with LVADs.