The hypothalamus senses low circulating levels of thyroid hormone and responds by releasing thyrotropin releasing hormone (TRH). The TRH stimulates the pituitary to produce thyroid stimulating hormone (TSH). The TSH, in turn, stimulates the thyroid to produce thyroid hormone until levels in the blood return to normal. Thyroid hormone exerts negative feed back control over the hypothalamus as well as anterior pituitary thus controlling the release of both TRH from hypothalamus and TSH from anterior pituitary gland