Hypothyroidism

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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 thyroiditis, causes the majority of cases, whereas in highly iodine ~~deficient~~-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 hypothyroidism, whereas pathology which affects the pituitary and hypothalamic production of thyroid ~~stimulating~~-stimulating hormone (TSH) and/or thyroid releasing hormone (TRH) (respectively) is referred to as secondary hypothyroidism. Common etiological associations are as follows ¹:

primary hypothyroidism
- autoimmunity
  - chronic
- iodine deficiency
  - iodine ~~induced~~-induced hypothyroidism
- thyroiditis
  - postpartum thyroiditis
  - subacute thyroiditis
  - riedel thyroiditis
  - silent thyroiditi s
  - Van Wyk Grumbach syndrome(rare) ⁴
- post-radiation
- infiltrative disease
secondary hypothyroidism
- pituitary adenoma
- panhypopituitarism
- post-radiation
- infiltrative disease
congenital
- mnemonic
drug-induced
- amiodarone

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 href="/articles/hashimoto-thyroiditis">Hashimoto 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 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>
-</ul><h4>Pathology</h4><h5>Etiology</h5><p>Pathology of the thyroid gland itself may result in primary hypothyroidism, whereas pathology which affects the pituitary and hypothalamic production of thyroid stimulating hormone (TSH) and/or thyroid releasing hormone (TRH) (respectively) is referred to as secondary hypothyroidism. Common etiological associations are as follows <sup>1</sup>:</p><ul>
+</ul><h4>Pathology</h4><h5>Etiology</h5><p>Pathology of the thyroid gland itself may result in primary hypothyroidism, whereas pathology which affects the pituitary and hypothalamic production of thyroid-stimulating hormone (TSH) and/or thyroid releasing hormone (TRH) (respectively) is referred to as secondary hypothyroidism. Common etiological associations are as follows <sup>1</sup>:</p><ul>
~~-<li>iodine deficiency<ul><li><a 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>
~~-<a href="/articles/subacute-lymphocytic-thyroiditis">silent thyroiditi</a><a title="Silent thyroiditis" href="/articles/subacute-lymphocytic-thyroiditis">s</a>~~
+<a href="/articles/subacute-lymphocytic-thyroiditis">silent thyroiditi</a><a href="/articles/subacute-lymphocytic-thyroiditis">s</a>