The thyroid is a gland in the body which produces two hormones T3 and T4. Pituitary is another gland which is the master gland of the body which secretes thyroid stimulating hormone which stimulate the thyroid to release T3 and T4. If the thyroid is functioning excessively T3 and T4 increases in the body and pituitary gets a message. So the TSH is secreted less and thyroid is less stimulated and T3, T4 levels come back to normal. The condition where T# T4 is elevated and TSH is less is called hy