Search results
Results from the WOW.Com Content Network
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]
A low TSH level typically indicates that the pituitary gland is being inhibited or "instructed" by the brain to cut back on stimulating the thyroid gland, having sensed increased levels of T 4 and/or T 3 in the blood. In rare circumstances, a low TSH indicates primary failure of the pituitary, or temporary inhibition of the pituitary due to ...
TSH levels are determined by a classic negative feedback system in which high levels of T3 and T4 suppress the production of TSH, and low levels of T3 and T4 increase the production of TSH. TSH levels are thus often used by doctors as a screening test, where the first approach is to determine whether TSH is elevated, suppressed, or normal. [25]
The disorder results from an antibody, called thyroid-stimulating immunoglobulin (TSI), that has a similar effect to thyroid stimulating hormone (TSH). [1] These TSI antibodies cause the thyroid gland to produce excess thyroid hormones. [1] The diagnosis may be suspected based on symptoms and confirmed with blood tests and radioiodine uptake.
The elevation is usually a marked increase over the normal range. [13] TSH is the preferred initial test of thyroid function as it has a higher sensitivity to changes in thyroid status than free T 4. [64] Biotin can cause this test to read "falsely low". [21]
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 therapy.
In children, late blood sampling at 60 to 120 minutes is necessary. An increase in the serum TSH level following TRH administration means that the cause of the hypothyroidism is in the hypothalamus (tertiary hypothyroidism), i.e. the hypothalamus is not producing TRH. Therefore, when TRH is given exogenously, TSH levels increase.
The TSH, in turn, stimulates the thyroid to produce thyroid hormone until levels in the blood return to normal. Thyroid hormone exerts negative feedback control over the hypothalamus as well as anterior pituitary, thus controlling the release of both TRH from hypothalamus and TSH from anterior pituitary gland.