Secondary hypothyroidism

Secondary hypothyroidism is a rare condition characterized by inadequate levels of thyroid hormone in the body due to a problem with the pituitary gland. Unlike primary hypothyroidism, which is caused by a problem with the thyroid gland itself, secondary hypothyroidism occurs when the pituitary gland fails to produce enough thyroid stimulating hormone (TSH) to stimulate the thyroid gland to produce thyroid hormone.

Causes

Secondary hypothyroidism is most commonly caused by damage to the pituitary gland. This can occur as a result of a pituitary tumor, surgery or radiation treatment to the pituitary, or diseases that infiltrate the pituitary, such as sarcoidosis or histiocytosis. In rare cases, secondary hypothyroidism can be caused by a congenital defect in the pituitary gland or by a problem with the hypothalamus, a part of the brain that controls the pituitary gland.

Symptoms

The symptoms of secondary hypothyroidism are similar to those of primary hypothyroidism and can include fatigue, weight gain, cold intolerance, constipation, dry skin, and depression. However, because the problem is with the pituitary gland rather than the thyroid gland, people with secondary hypothyroidism may also have symptoms related to other hormonal deficiencies, such as decreased libido, infertility, and irregular menstrual periods in women.

Diagnosis

Diagnosis of secondary hypothyroidism involves blood tests to measure levels of TSH and thyroid hormone. In secondary hypothyroidism, TSH levels are low or normal, while thyroid hormone levels are low. This is in contrast to primary hypothyroidism, where TSH levels are high. Imaging tests, such as an MRI or CT scan, may also be used to check for a pituitary tumor or other abnormalities.

Treatment

Treatment for secondary hypothyroidism involves replacing the missing thyroid hormone with a synthetic version. This is usually taken as a daily pill. In addition, any underlying cause, such as a pituitary tumor, needs to be treated.

See also

• Hypothyroidism
• Pituitary gland
• Thyroid hormone
• Thyroid-stimulating hormone

Secondary hypothyroidism Resources
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