The |thyroid| gland is one of the |glands| of the endocrine system which lies outside of a body cavity. It is a small gland weighing about 1 ounce (28 grams) and is located in the neck, just below the |larynx|. This gland secretes two ~hormones~: thoroxine and calcitonin (thyrocalcitonin). Thoroxine effects the growth rate and metabolism of all of the body's cells. It controls ~reflexes~ and regulates the rate at which the body produces energy and transforms food into body components. This ~hormone~ causes cells to speed up the release of energy from foods as needed by stimulating catabolism (increasing basal metabolism). All body functions depend upon the normal supply of energy, normal |thyroid| secretion is, therefore, vital to the body. One of the main components of thoroxyne is ~iodine~, an important body building agent. Babies cannot grow properly without ~iodine~. In older people, ~iodine~ deficiency causes hair loss, slowed speech, and drying and thickening of the skin. An average adults ~iodine~ requirement is only about a millionth of an ounce (0.00003 grams) per day but it is vital to the delicate balance between health and sickness. ~Thyroxine~ also controlls temperature. People with overactive |thyroid| |glands| tend to feel uncomfortably hot in cool conditions, while those whose |thyroid| gland is under-active tend to feel cool even on hot days. The other ~hormone~ produced by the |thyroid| gland, calcitonin, tends to decrease the amoumt of calcium in the ~blood~, the opposite effect of parathormone from the |parathyroid| |glands|. Calcitonin functions to help maintain homeostasis of ~blood~ clavium. It prevents a harmful excess of calcium in the ~blood~, called hypercemia, from developing.
