Abstract: This invention relates to a composition for use in the treatment or prevention of iodine deficiency diseases or disorders such as fibrocystic dysplasia of the breast, breast cancer, endometriosis, ovarian cysts and premenstrual syndrome. More particularly, this invention relates to a composition for the treatment or prevention of iodine deficiency diseases or disorders, the composition comprising elemental iodine (I.sub.2) which may also be referred to as metallic iodine or iodine metal. The elemental iodine can be used with any pharmaceutically acceptable carrier.