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.
