any of the hormones broken down and dispersed by the thyroid gland. The primary thyroid hormone thyroxine (T4), is metabolized to triiodothyronine (T) within target tissues. Plasma amounts in T4 are much greater than those in T but T has the more potent physiological behavior. Both hormones play a core part in regulating fundamental metabolic procedures and the formative development and differentiation of the brain. Excess secretions of these hormones have substantial impacts on metabolism and mental operation
THYROID HORMONES: "The imbalance or excess of thyroid hormones often produces symptoms that are overlooked and confused with other disorders, commonly of a neurological or psychiatric nature."