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Thyroid-stimulating hormone (also known as thyrotropin, thyrotropic hormone, or abbreviated TSH) is a pituitary hormone that stimulates the thyroid gland to produce thyroxine (T 4 ), and then triiodothyronine (T 3) which stimulates the metabolism of almost every tissue in the body. [ 1] It is a glycoprotein hormone produced by thyrotrope cells ...
Thyroid hormones are any hormones produced and released by the thyroid gland, namely triiodothyronine ( T3) and thyroxine ( T4 ). They are tyrosine -based hormones that are primarily responsible for regulation of metabolism. T 3 and T 4 are partially composed of iodine, derived from food. [ 2] A deficiency of iodine leads to decreased ...
Because a single abnormal TSH level can be misleading, T3 and T4 levels must be measured in the blood to further confirm the diagnosis. When circulating in the body, T3 and T4 are bound to transport proteins. Only a small fraction of the circulating thyroid hormones are unbound or free, and thus biologically active. T3 and T4 levels can thus be ...
Subclinical hypothyroidism is a biochemical diagnosis characterized by an elevated serum TSH level, but with a normal serum free thyroxine level. [ 48 ] [ 49 ] [ 50 ] The incidence of subclinical hypothyroidism is estimated to be 3-15% and a higher incidence is seen in elderly people, females and those with lower iodine levels. [ 48 ]
The diagnosis of hyperthyroidism is confirmed by blood tests that show a decreased thyroid-stimulating hormone (TSH) level and elevated T 4 and T 3 levels. TSH is a hormone made by the pituitary gland in the brain that tells the thyroid gland how much hormone to make. When there is too much thyroid hormone, the TSH will be low.
Hypothyroidism is common in pregnancy with an estimated prevalence of 2-3% and 0.3-0.5% for subclinical and overt hypothyroidism respectively. [8] Endemic iodine deficiency accounts for most hypothyroidism in pregnant women worldwide while chronic autoimmune thyroiditis is the most common cause of hypothyroidism in iodine sufficient parts of the world.
In such a case a TRH stimulation test, in which TRH is given and TSH levels are measured at 30 and 60-minutes after, may be conducted. [84] T 3 and T 4 can be measured directly. However, as the two thyroid hormones travel bound to other molecules, and it is the "free" component that is biologically active, free T 3 and free T 4 levels can be ...
Thyroid function tests ( TFTs) is a collective term for blood tests used to check the function of the thyroid. [ 1] TFTs may be requested if a patient is thought to suffer from hyperthyroidism (overactive thyroid) or hypothyroidism (underactive thyroid), or to monitor the effectiveness of either thyroid-suppression or hormone replacement ...