What releases TSH?

The hypothalamus is a brain region that releases the thyrotropin releasing hormone (TRH) to stimulate the anterior pituitary gland to release thyroid stimulating hormone (TSH). TSH in turn goes on to regulate secretion of thyroid hormones. When TSH levels are high, it suppresses TRH synthesis and release from the hypothalamus. When TSH levels drop, this negative feedback stops and the hypothalamus secretes TRH, which will stimulate the pituitary to release more TSH.