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A TSH (Thyroid Stimulating Hormone) test is performed to check for thyroid gland malfunctions. The hypothalamus releases TRH (Thyrotopin Release Hormone). TRH then generates the pituitary gland to release TSH. Triiodothyronine (T3) and Thyroxin (T4) are produced by the thyroid once TSH instigates their release. Both an underactive and overactive thyroid can cause a multitude of health problems.
TSH (Thyroid Stimulating Hormone) is a hormone produced by the pituitary gland, and not by the thyroid as it may seem. The purpose of TSH is to stimulate the thyroid to produce more thyroid hormone. High TSH levels typically indicates that the body is not receiving enough thyroid hormone. A low TSH level is indicative of the body receiving too much thyroid hormone. Testing for T4, free T3 (Triiodothyronine) and thyroid antibodies can also be performed to ensure that the problem lies within the thyroid itself and not in the hypothalamus or the pituitary gland.
The tests are performed by drawing blood from the patient when ordered by a physician. It is typically ordered when the physician feels that the patient may have one of two conditions, hypothyroidism or hyperthyroidism. They are also performed on a routine basis for people who have already been diagnosed with either of the two conditions.
The normal range for TSH level is 0.4 to 4.0 mlU/L (milli-international units per liter). People without symptoms or signs of an abnormally functioning thyroid may have a TSH level of 2.0 mlU/L and T4 (Thyroxine) levels are still at risk of developing hypothyroidism in the future.
Hypothyroidism occurs when the thyroid functions at below normal levels and is often referred to as an underactive thyroid. A low level of TSH and high level of T4 (Thyroxine) indicate hypothyroidism. The Mayo Clinic states that hypothyroidism is more common in women, particularly in women over the age of 50. Chemical reactions are upset by hypothyroidism 1.
In early stages of hypothyroidism it is not uncommon to have little or no symptoms, however joint pain, obesity, heart disease and infertility can occur later. Hypothyroidism can be controlled by the proper dosage of synthetic thyroid hormone.
Hyperthyroidism, also known as overactive thyroid, occurs when T4 levels are overproduced by the thyroid while TSH is either extremely low or nonexistent. An accelerated metabolism is one sign of an overactive thyroid, causing someone to feel irritable, sudden and rapid weight loss, rapid or irregular heart rate, sweating and nervousness are other symptoms. Several methods exist for treating hyperthyroidism, from anti-thyroid medications to radioactive iodine, which helps to slow down the rate at which the thyroid produces T4.
Complications of High TSH Levels
If left untreated, a high TSH level can lead to a number of larger problems. Hashimoto's Thyroiditis occurs when the immune system attacks the thyroid. A goiter occurs when the thyroid is left untreated and continues to enlarge and typically coincides with Hashimoto’s Thyroiditis.
Myxedema coma, although exceedingly atypical, can also occur when the thyroid is left untreated. Infertility, increased risk or heart disease, and birth defects are other complications that may happen when high TSH levels are left undiagnosed.