What is thyroid-stimulating hormone (TSH)?
The thyroid gland is a gland situated in the neck and secretes the thyroid hormones thyroxine (T4) and tri-iodothyronine (T3). These hormones are essential for the normal growth and metabolism of all body tissues and control the basal metabolic rate. They also play an important role in of proteins, carbohydrate and lipid metabolism. An example of this is the raised cholesterol levels in patients with hypothyroidism. For the thyroid to be able to secrete these hormones, it needs to be stimulated. TSH is a hormone secreted by the pituitary gland in the brain. The pituitary gland is under the control of another section of the brain, the hypothalamus, where another hormone, thyroid-releasing hormone (TRH) is secreted. TRH stimulates the secretion of TSH. TSH travels from the pituitary gland in the bloodstream to the thyroid, where it stimulates the secretion of thyroid hormones, T4 and T3. If the patient’s thyroid is producing excess thyroid hormone (hyperthyroidism or thyrotoxicosis), the
