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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]
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.
Thyroid-stimulating hormone (TSH) released from the anterior pituitary (also known as the adenohypophysis) binds the TSH receptor (a G s protein-coupled receptor) on the basolateral membrane of the cell and stimulates the endocytosis of the colloid. The endocytosed vesicles fuse with the lysosomes of the follicular cell.
Therefore, when TRH is given exogenously, TSH levels increase. If the increase in serum TSH level following TRH administration is absent or very slight, then the cause of the hypothyroidism is in the anterior pituitary gland, i.e. the pituitary is not secreting TSH. Therefore, even when TRH is given exogenously, TSH levels do not rise as the ...
A fasting response is common in critical illness. NTIS as a result of fasting may be regarded as a healthy and adaptive mechanism that reduces energy expenditure. [10] Fasting in healthy, euthyroid people causes reduced T3 and elevated rT3, although TSH is usually unchanged. [3] [5] [10] Even moderate weight loss can lower T3. [2]
Thyroid function tests include a battery of blood tests, including the measurement of the thyroid hormones, as well as the measurement of thyroid stimulating hormone (TSH). [84] They may reveal hyperthyroidism (high T 3 and T 4 ), hypothyroidism (low T 3 , T 4 ), or subclinical hyperthyroidism (normal T 3 and T 4 with a low TSH).
The TSH receptor is a member of the G protein-coupled receptor superfamily of integral membrane proteins [5] and is coupled to the G s protein. [6] It is primarily found on the surface of the thyroid epithelial cells, but also found on adipose tissue and fibroblasts. The latter explains the reason of the myxedema finding during Graves disease.
In 1971, the thyroid stimulating hormone (TSH) radioimmunoassay was developed, which was the most specific marker for assessing thyroid status in patients. [82] Many people who were being treated based on basal metabolic rate, minimizing hypothyroid symptoms, or based on serum protein-bound iodine, were found to have excessive thyroid hormone. [82]