Overview:    Thyroxine (T4) and triiodothyronine (T3) are thyroid hormones secreted by thyroid gland. Disturbance of these hormones causes wide range of health problems in the body.    Thyroid gland is one of the largest of the endocrine glands ,weighing 15 to 20 grams in adults. The gland is located immediately below the larynx on each side of and anterior to the trachea ....