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Know About Neonatal Thyroid Stimulating Hormone # (TSH)
Thyroid-stimulating hormone (TSH) is produced by the pituitary gland, a tiny organ located below the brain and behind the sinus cavities. TSH stimulates the thyroid gland to release the hormones thyroxine (T4) and triiodothyronine (T3) into the blood. These thyroid hormones help control the rate at which the body uses energy. This test measures the amount of TSH in the blood.
Pituitary-Thyroid Feedback System
TSH, along with its regulatory hormone thyrotropin releasing hormone (TRH), which comes from the hypothalamus, is part of the feedback system that the body uses to maintain stable amounts of thyroid hormones in the blood. When thyroid hormone concentrations decrease, the production of TSH by the pituitary gland is increased. TSH in turn stimulates the production and release of T4 and T3 by the thyroid gland, a small butterfly-shaped gland that lies at the base of the throat flat against the windpipe. When all three organs are functioning normally, thyroid production turns on and off to maintain relatively stable levels of thyroid hormones in the blood.
If the thyroid releases inappropriately large amounts of T4 and T3, the affected person may experience symptoms associated with hyperthyroidism, such as rapid heart rate, weight loss, nervousness, hand tremors, irritated eyes, and difficulty sleeping. Graves disease is the most common cause of hyperthyroidism. It is a chronic autoimmune disorder in which the affected person's immune system produces antibodies that act like TSH, leading to the production of excessive amounts of thyroid hormone. In response, the pituitary may produce less TSH, usually leading to a low level in the blood.
If there is decreased production of thyroid hormones by the thyroid (hypothyroidism), the person may experience symptoms such as weight gain, dry skin, constipation, cold intolerance, and fatigue. Hashimoto thyroiditis is the most common cause of hypothyroidism in the U.S. It is a chronic autoimmune condition in which the immune response causes inflammation and damage to the thyroid as well as the production of autoantibodies. With Hashimoto thyroiditis, the thyroid produces low levels of thyroid hormone. The pituitary may produce more TSH, usually resulting in a high level in the blood.
However, the level of TSH does not always predict or reflect thyroid hormone levels. Some people produce an abnormal form of TSH that does not function properly. They often have hypothyroidism despite having normal or even mildly elevated TSH levels. In a variety of thyroid diseases, thyroid hormone levels may be high or low, regardless of the amount of TSH present in the blood.
Rarely, pituitary dysfunction may result in increased or decreased amounts of TSH. In addition to pituitary dysfunction, hyperthyroidism or hypothyroidism can occur if there is a problem with the hypothalamus (insufficient or excessive TRH).
TSH test is done to screen for and help diagnose thyroid disorders; to monitor treatment of hypothyroidism and hyperthyroidism. For screening: Newborn screening is widely recommended; however, there is no consensus within the medical community as to the age adult screening should begin or whether screening should be done.
For monitoring treatment: as directed by your healthcare provider
Otherwise: when a person has symptoms of hyperthyroidism or hypothyroidism and/or an enlarged thyroid.
A health practitioner may order a TSH test when someone has symptoms of hyperthyroidism or hypothyroidism and/or when a person has an enlarged thyroid gland (goiter).
Signs and symptoms of hyperthyroidism may include:
Increased heart rate
Tremors in the hands
Light sensitivity, visual disturbances
The eyes may be affected: puffiness around the eyes, dryness, irritation, and, in some cases, bulging of the eyes.
Signs and symptoms of hypothyroidism may include:
Menstrual irregularity in women
TSH may be ordered at regular intervals when an individual is being treated for a known thyroid disorder. When a person's dose of thyroid medication is adjusted, the American Thyroid Association recommends waiting 6-8 weeks before testing the level of TSH again.