People with an underactive thyroid often feel lethargic, experience weight gain and feel the cold. Their thyroid gland may enlarge to produce a goitre. Treatment is medication in the form of tablets to bring the level of thyroid hormones back to normal. This also reduces the amount of thyroid stimulating hormone in circulation. It is particularly important for pregnant women to have the correct amounts of thyroid stimulating hormone and thyroid hormones to ensure the healthy development of their babies.
Thyroid stimulating hormone is one of the hormones measured in newborns. Rarely, problems from the pitutiary gland or rare genetic conditions can result in inappropriately high thyroid stimulating hormones, and high free thyroid hormone levels. If a person has too little thyroid stimulating hormone, it is most likely that their thyroid gland is making too much thyroid hormone, that is, they have an overactive thyroid or hyperthyroidism , which is suppressing the thyroid stimulating hormone.
People with an overactive thyroid have the opposite symptoms to those with hypothyroidism, i. They may also have a slightly enlarged thyroid gland. Treatment is medication in the form of tablets, which reduce the activity of the thyroid gland and return all thyroid hormone levels to normal. Rarely, problems in the pituitary gland can also result in a low thyroid stimulating hormone, and low free thyroid hormone levels.
About Contact Events News. Thyroid Hormone Production and Function. Topic Overview The thyroid gland uses iodine from food to make two thyroid hormones: triiodothyronine T3 and thyroxine T4. When the hypothalamus and pituitary are working normally, they sense when: Thyroid hormone levels are low, so they secrete more TRH and TSH, which stimulates the thyroid to make more hormones.
Thyroid hormone levels are too high, so they secrete less TRH and TSH, which reduces hormone production by the thyroid. Disease or tumors of the pituitary gland can affect this process. Thyroid hormones affect every cell and all the organs of the body. They: Regulate the rate at which calories are burned, affecting weight loss or weight gain. Can slow down or speed up the heartbeat.
Can raise or lower body temperature. Influence the rate at which food moves through the digestive tract. Control the way muscles contract. The alpha subunit of TSH is also present in two other pituitary glycoprotein hormones, follicle-stimulating hormone and luteinizing hormone , and, in primates, in the placental hormone chorionic gonadotropin. Each of these hormones also has a unique beta subunit, which provides receptor specificity. Free alpha and beta subunits have essentially no biological activity.
The most important controller of TSH secretion is thyroid-releasing hormone. Thyroid-releasing hormone is secreted by hypothalamic neurons into hypothalamic-hypophyseal portal blood, finds its receptors on thyrotrophs in the anterior pituitary and stimulates secretion of TSH.
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