Iodine is essential for the normal functioning of the human body. Iodine deficiency causes symptoms such as dry skin, hair loss, swollen face and thyroid gland, weak muscles, weight gain, mental sluggishness, and fatigue. This condition is rare in the West because potassium iodide (a salt of iodine) is added to table salt. Iodum is used mainly to treat symptoms associated with an overactive thyroid. These include eye pain, enlarged glands, and a ravenous appetite but a tendency to lose weight and to feel weak from hunger. The slightest physical exertion causes sweating. People who require this remedy have an obsessive desire to keep frantically busy because they get persistent frightening thoughts when they have to sit and remain still. However, their excessive activity is not organized, making them extremely forgetful, and leads to constant rechecking, for example, to make sure that they have locked the doors at night. They are talkative and are excessively restless mentally. Iodum is also used to treat disorders of the mucous membranes (particularly those of the larynx) and the heart and blood vessels. It is also given for bone pain that comes on at night and deep, hacking toughs. While some thyroid disease is due to iodine deficiency, thyroids are extremely sensitive to iodine, and adding too much iodine to the diet as it can irritate or aggravate the thyroid.