Thyroid-stimulating hormone (TSH, thyrotropin) is generally increased in hypothyroidism and decreased in hyperthyroidism,[2] making it the most important test for early detection of both of these conditions.[3][4] The result of this assay is suggestive of the presence and cause of thyroid disease, since a measurement of elevated TSH generally indicates hypothyroidism, while a measurement of low TSH generally indicates hyperthyroidism.[2] However, when TSH is measured by itself, it can yield misleading results, so additional thyroid function tests must be compared with the result of this test for accurate diagnosis.[4][5][6]