what is a tsh blood test
Thyroid-Stimulating Hormone (TSH). Guide. A thyroid-stimulating hormone (TSH) blood test is used to check for thyroid gland problems. TSH is produced when the hypothalamus releases a substance called thyrotropin-releasing hormone (TRH). TRH then triggers the pituitary gland to release TSH. Find the cause of an underactive thyroid gland (hypothyroidism). 2  TSH levels can help determine whether hypothyroidism is due to a damaged thyroid gland or some other cause (such as a problem with the pituitary gland or the hypothalamus).