Thyroid-stimulating hormone or TSH is released by the pituitary gland and activates the thyroid gland, which in turn releases two other hormones, T3 and T4. If the thyroid releases less T3 and T4 than normal, the pituitary will increase production of TSH.
The TSH Test
TSH refers not only to the hormone, but also to the test used to measure levels. Results of the simple and routine blood test to measure TSH levels should arrive in just a day or two after having blood drawn.
The Normal Range
Normal ranges of TSH vary depending on whether the patient is already being treated for a thyroid condition. According to the National Institutes of Health, the normal range for those who are untreated for a thyroid condition is between 0.4 and 4.0 mlU/L, while the range is between 0.5 and 3.0 mlU/L for those already being treated for a thyroid condition.
If TSH levels measure above the normal range, a doctor may diagnose the condition as hypothyroidism. Hypothyroidism can be caused by inflammation or infection of the thyroid or can be the result of a damaged thyroid gland or pituitary gland.
Symptoms of Hypothyroidism
While the symptoms and severity of symptoms of high TSH can vary from person to person, the most common symptoms include fatigue, mood swings, intolerance to cold temperatures, pale and dry skin, muscle pain and depression.
Treatment of Hypothyroidism
The most common treatment for high TSH levels is through synthetic TSH administered daily in pill form. In cases where hypothyroidism is caused by a tumor on the pituitary gland, treatment may include surgery and removal of the growth.