Physiological Effects of the Thyroid Hormones

The thyroid gland has a powerful influence over the activities of the whole body. If the function of the gland is for any reason lost, serious disturbances of chemical and morphological structure arise and are manifested as physical and mental disorders. The diversity of the action of thyroid hormones on physiological functions, on the metabolic rate, and on the activity of various enzyme systems both in the body as a whole and in tissue preparations has been known for a long time. Our knowledge of the role of thyroid hormones is based on experiments in which a particular thyroid hormone has been given to healthy and athyrotic animals and on extensive clinical observations on patients with hyperthyroid and hypothyroid states.