Hypothyroidism

Changed by David Carroll, 14 Mar 2019

Updates to Article Attributes

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The clinical syndrome of hypothyroidism is marked by inadequate thyroid hormone production, resulting in a decreased rate of cellular metabolism. It may be primary, in which the dysfunction pertains to the thyroid gland itself, or secondary, due to hypothalamic or pituitary dysfunction 1.

Epidemiology

Disproportionately affects females in a 10:1 ratio compared to males. Clinically symptomatic hypothyroidism is less common than subclinical hypothyroidism, and becomes more common with increasing age. The most common cause depends on the patient population; in the United States autoimmune diseases, especially hashimoto's thyroiditis, causes the majority of cases, whereas in highly iodine deficient populations (such as those who reside in Southeast Asia, especially populations further inland) iodine deficiency is the most common cause 3.

Clinical presentation

Hypothyroidism affects almost every organ system, with common presenting complaints including:

  • shortness of breath
  • muscle/joint pain
  • hoarseness
  • periorbital/peripheral (non-pitting) edema
  • weight gain
  • menstrual irregularity
ECG
  • sinus bradycardia
  • prolonged QT interval
  • flattening/inversion of T waves
  • interventricular conduction delays
    • especially right bundle branch block 2

Pathology

Etiology

Pathology of the thyroid gland itself may result in primary hypothyroisim, whereas pathology which affects the pituitary and hypothalamic production of TSH and/or TRH (respectively) is referred to as secondary hypothyroidism. Common etiological associations are as follows 1:

Radiographic features

Ultrasound

Sonographic appearance depends on underlying etiology, and may include:

  • abnormal size of the thyroid gland
  • alteration in thyroid echotexture
    • may be diffuse or nodular
  • abnormal color flow Doppler patterns
  • -<p>The clinical syndrome of <strong>hypothyroidism</strong> is marked by inadequate thyroid hormone production, resulting in a decreased rate of cellular metabolism. It may be primary, in which the dysfunction pertains to the thyroid gland itself, or secondary, due to hypothalamic or pituitary dysfunction <sup>1</sup>.</p><h4>Epidemiology</h4><p>Disproportionately affects females in a 10:1 ratio compared to males. Clinically symptomatic hypothyroidism is less common than subclinical hypothyroidism, and becomes more common with increasing age. The most common cause depends on the patient population; in the United States autoimmune diseases, especially <a title="Hashimoto's thyroiditis" href="/articles/hashimoto-thyroiditis">hashimoto's thyroiditis</a>, causes the majority of cases, whereas in highly iodine deficient populations (such as those who reside in Southeast Asia, especially populations further inland) iodine deficiency is the most common cause <sup>3</sup>.</p><h4>Clinical presentation</h4><p>Hypothyroidism affects almost every organ system, with common presenting complaints including:</p><ul>
  • +<p>The clinical syndrome of <strong>hypothyroidism</strong> is marked by inadequate thyroid hormone production, resulting in a decreased rate of cellular metabolism. It may be primary, in which the dysfunction pertains to the thyroid gland itself, or secondary, due to hypothalamic or pituitary dysfunction <sup>1</sup>.</p><h4>Epidemiology</h4><p>Disproportionately affects females in a 10:1 ratio compared to males. Clinically symptomatic hypothyroidism is less common than subclinical hypothyroidism, and becomes more common with increasing age. The most common cause depends on the patient population; in the United States autoimmune diseases, especially <a href="/articles/hashimoto-thyroiditis">hashimoto's thyroiditis</a>, causes the majority of cases, whereas in highly iodine deficient populations (such as those who reside in Southeast Asia, especially populations further inland) iodine deficiency is the most common cause <sup>3</sup>.</p><h4>Clinical presentation</h4><p>Hypothyroidism affects almost every organ system, with common presenting complaints including:</p><ul>
  • -<a title="Autoimmune thyroiditis" href="/articles/autoimmune-thyroiditis">autoimmunity</a><ul><li><a title="Chronic autoimmune thyroiditis" href="/articles/hashimoto-thyroiditis">chronic</a></li></ul>
  • +<a href="/articles/autoimmune-thyroiditis">autoimmunity</a><ul><li><a href="/articles/hashimoto-thyroiditis">chronic</a></li></ul>
  • -<li>iodine deficiency<ul><li><a title="Iodine induced hypothyroidism" href="/articles/wolff-chaikoff-effect">iodine induced hypothyroidism</a></li></ul>
  • +<li>iodine deficiency<ul><li><a href="/articles/wolff-chaikoff-effect">iodine induced hypothyroidism</a></li></ul>
  • -<li><a title="Post partum thyroiditis" href="/articles/post-partum-thyroiditis">post-partum thyroiditis</a></li>
  • -<li><a title="De Quervain thyroiditis" href="/articles/de-quervain-thyroiditis">subacute thyroiditis</a></li>
  • -<li><a title="Riedel thyroiditis" href="/articles/riedel-thyroiditis">riedel thyroiditis</a></li>
  • -<li><a title="Silent thyroiditis" href="/articles/subacute-lymphocytic-thyroiditis">silent thyroiditis</a></li>
  • +<li><a href="/articles/post-partum-thyroiditis">post-partum thyroiditis</a></li>
  • +<li><a href="/articles/de-quervain-thyroiditis">subacute thyroiditis</a></li>
  • +<li><a href="/articles/riedel-thyroiditis">riedel thyroiditis</a></li>
  • +<li><a href="/articles/subacute-lymphocytic-thyroiditis">silent thyroiditis</a></li>
  • -<li><a title="Lymphoma" href="/articles/lymphoma">lymphoma</a></li>
  • -<li><a title="Amyloidosis" href="/articles/amyloidosis">amyloidosis</a></li>
  • -<li><a title="Sarcoidosis" href="/articles/sarcoidosis-1">sarcoidosis</a></li>
  • -<li><a title="Tuberculosis" href="/articles/tuberculosis">tuberculosis</a></li>
  • +<li><a href="/articles/lymphoma">lymphoma</a></li>
  • +<li><a href="/articles/amyloidosis">amyloidosis</a></li>
  • +<li><a href="/articles/sarcoidosis-1">sarcoidosis</a></li>
  • +<li><a href="/articles/tuberculosis">tuberculosis</a></li>
  • -<li><a title="Pituitary adenoma" href="/articles/pituitary-adenoma">pituitary adenoma</a></li>
  • +<li><a href="/articles/pituitary-adenoma">pituitary adenoma</a></li>
  • -<a title="Congenital hypothyroidism" href="/articles/congenital-hypothyroidism">congenital</a><ul><li><a title="Congenital hypothyroidism (mnemonic)" href="/articles/congenital-hypothyroidism-mnemonic">mnemonic </a></li></ul>
  • +<a href="/articles/congenital-hypothyroidism">congenital</a><ul><li><a href="/articles/congenital-hypothyroidism-mnemonic">mnemonic </a></li></ul>

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