Your thyroid is a bow-tie shaped gland located in the front of your neck. It produces hormones that regulate the metabolism of cells throughout your body through a two-way interaction with your brain. When thyroid hormone levels are low, a part of the brain called the hypothalamus produces thyrotropin releasing hormone or TRH. TRH causes the pituitary gland at the base of the brain to produce thyroid stimulating hormone, or TSH. And TSH signals the thyroid to increase production of its hormones. When blood levels of thyroid hormones increase, the hypothalamus and pituitary gland decrease production of TRH and TSH. Sometimes the thyroid gland cannot produce enough hormones, but the pituitary gland continues to send TSH to the thyroid. This can cause the thyroid to become enlarged.