During the 1921 American Medical Association (AMA) convention, two Ohio doctors presented findings from their clinical trial demonstrating the effectiveness of sodium iodide treatments for the prevention of goiter in Akron schoolgirls. Prior to their study, research from Europe had also suggested an association between iodine deficiency and goiter (enlarged thyroid gland). It was found that without iodine, the body could not properly synthesize thyroid hormones, which often resulted in an unsightly neck goiter or in more serious cases, mental retardation. Iodine deficiency generally occurs in areas where the soil has been depleted of iodine because of flooding, heavy rainfall, or glaciation.