by Walter Little

Created on: January 28, 2010   Last Updated: February 11, 2010

What is Hypothyroidism

 Hypothyroidism is a disease found in both humans and animals and is caused by insufficient production of the thyroid hormone. In an infant, the condition is known as Cretinism1.

About three percent (3%) of the general population is hypothyroidic3 or as a result of either an absent thyroid gland or a deficiency in stimulating hormones from either the hypothalamus or pituitary. It – Hypothyroidism – can also result from postpartum thyroiditis – a condition which affects about five percent (5%) of all women within a year of giving birth. The first phase is typically hyperthyroidism; the thyroid then either returns to normal, or a woman develops hypothyroidism. Of the women who experience the latter associated with postpartum thyroiditis, one in five will develop permanent hypothyroidism requiring life-long treatment.

Temporary hypothyroidism can also be due to Wolff-Chaikoff effect4. A very high intake of iodine can be used to temporarily treat hyperthyroidism in an emergency situation. Although iodine is substrate for thyroid hormones, high levels prompt the thyroid gland to take in less of the iodine that is eaten, reducing hormone production.

Hypothyroidism is often classified by the organ of origin:

Type

Origin

Description

Primary

Thyroid gland

The most common forms include Hashimoto's thyroiditis (an auto-immune disease) and radioiodine therapy for hyperthyroidism.

Secondary

Pituitary gland

Occurs if the pituitary gland does not create enough thyroid stimulating hormone (TSH) to induce the thyroid gland to produce enough Thyroxine and Triiodothyronine. Although not every case of secondary hypothyroidism has a clear-cut cause, it is usually caused by damage to the pituitary gland either by tumor, radiation, or surgery

Tertiary

Hypothalamus

Results when the hypothalamus fails to produce sufficient thyrotropin-releasing hormone (TRH). TRH prompts the pituitary gland to produce thyroid stimulating hormone (TSH).

General psychological associations

Hypothyroidism can also be caused by lithium-based mood stabilizers, usually used to treat bipolar disorder (previously known as manic depression).

In addition, patients with hypothyroidism and psychiatric symptoms may be diagnosed with:

Atypical depression (which may present as dysthymia5)

Bipolar spectrum syndrome (including bipolar I or bipolar II, cyclothymia, or premenstrual syndrome)

Inattentive ADHD or sluggish cognitive tempo

What are the symptoms of hypothyroidism?

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