Managing thyroid dysfunction in selected special situations

Abstract

Managing thyroid dysfunction is simple at first glance, the idea is to bring hormone levels in the euthyroid range, treat with antithyroid drugs, radio-iodine or surgery if toxic and replace with thyroxine or T3 if hypothyroid. Complexities arise when there are coexisting conditions that affect the thyroid or are affected by thyroid dysfunction and this review will deal with the special situations that need care when correcting thyroid hormone levels.

Effects of thyroid hormones on the heart

“…The improvement of the cardiac function after hormonal treatment is an important argument in favor of the implication of hypothyroidism in the genesis of DCM. 43,44 Atrial fibrillation and thyroid AF is the most common cardiac complication of hyperthyroidism, occurring in an estimated 10% to 25% of overtly hyperthyroid patients; in comparison 0.4% of the general population has AF, representing an independent risk factor for cardiovascular events.…”

Role of Thyroid Hormones in Different Aspects of Cardiovascular System

“…The physiological chronotropic response and normal tension of the heart muscle in diastolic phase depend on the proper expression of T3 in the heart cells and its stimulating influence on Na Dilated Cardiomyopathy [DCM] is a heart muscle disorder defined by the presence of a dilated and poorly functioning left ventricle in the absence of abnormal loading conditions [hypertension, valve disease] or ischemic heart disease sufficient to cause global systolic impairment; in hypothyroidism, although cardiac output is reduced, heart failure is relatively rare because there is a lower oxygen demand in the periphery. The improvement of the cardiac function after hormonal treatment is an important argument in favor of the implication of hypothyroidism in the genesis of DCM [43,44]. "Low T3 Syndrome" [LTS] is characterized by an isolated reduction of T3, with normal serum levels of TSH and T4, the principal pathophysiological mechanism underlying low circulating T3 is the reduced enzyme activity of 5'monodeiodinase, responsible for converting T4 into T3 in peripheral tissues.…”