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There are 4 glossary search results for:   hypothalamus




Definition:
Goiter is an enlargement of the thyroid gland caused most commonly by iodine deficiency in the diet. Iodine deficiency leads to low levels of thyroid hormone production, and a reduction in thyroid hormone negative feedback on the hypothalamus and the anterior pituitary leads to a compensatory rise in the thyroid stimulating hormone (TSH). Enlargement of the thyroid gland is, therefore, caused by abnormally high circulating levels of TSH, which has a strong trophic effect on the thyroid gland.



Definition:
Excessive appetite or consumption of food. It may be associated with damage to the hypothalamus. Also referred to as polyphagia.



Definition:
Hypothyroidism refers to a pathophysiological condition in which the thyroid gland does not produce sufficient amounts of the thyroid hormones (underactive thyroid), leading to abnormally low levels of the thyroid hormones (T3 and T4).

The symptoms of hypothyroidism may include reduced metabolic rate, chronic fatigue, weight gain, myxedema, and depression.

Three main forms of hypothyroidism exist: (1) Primary hypothyroidism, (2) Secondary hypothyroidism, and (3) Tertiary hypothyroidism.

In primary hypothyroidism, the thyroid gland itself is incapable of producing normal levels of the thyroid hormones.

Secondary hypothyroidism is caused by low levels of thyroid stimulating hormone (TSH). TSH, produced by the anterior pituitary gland, is required to stimulate the thyroid gland to produce the thyroid hormones.

Tertiary hypothyroidism is caused by low levels of thyrotropin releasing hormone (TRH). TRH, produced by the hypothalamus, is required to stimulate the anterior pituitary gland to produce TSH which, in turn, is required to stimulate the thyroid gland to produce the thyroid hormones.

Related glossary terms/phrases:
Primary hypothyroidism
Secondary hypothyroidism
Tertiary hypothyroidism

Hyperthyroidism
Euthyroidism



Definition:
Tertiary hypothyroidism is characterized by abnormally low levels of thyroid hormone (T3 and T4) production, where the defect is at the level of the hypothalamus.

In tertiary hypothyroidism, the hypothalamus is unable to produce sufficient levels of thyrotropin release hormone (TRH). Low TRH levels lead to low production of the thyroid stimulating hormone (TSH) by the anterior pituitary gland which, in turn, leads to insufficient stimulation of the thyroid gland to produce the thyroid hormones (T3 and T4).

Thus, in tertiary hypothyroidism, the circulating levels of TRH, TSH, T3, and T4 are all abnormally low.

Related glossary terms/phrases:
Hypothyroidism
Primary hypothyroidism
Secondary hypothyroidism









Posted: Sunday, March 31, 2013
Last updated: Friday, August 28, 2015