Case Workbook for Human Genetics 9th Edition by Ricki Lewis

Exercise 6

In Graves disease, the immune system attacks the thyroid gland, which normally produces hormones controlling energy utilization. Siblings of people with Graves disease are 15 times as likely to develop the disorder as people whose siblings are unaffected. Women develop the condition more often than men, and a high percentage of affected individuals smoke. Do you think that Graves disease is caused solely by an abnormal gene, solely by an environmental trigger, or might there be another explanation?