One study looks into large head size and the increase risk of cancers like thyroid cancer:
"If you have a large head circumference, new research coming out of the Cleveland Clinic says that you may be at an increased risk of thyroid cancer, as well as breast, colon and uterine cancers. The researchers define a "big" head as being a circumference larger than 22.8 inches (58 centimeters) in men and 22.4 inches (57 centimeters) in women. They recommend that people who have large heads be tested for Cowden Syndrome, a genetically transmitted condition, as well as screened for the cancers that are linked to that condition, which include colon, breast, thyroid and uterine cancers."
Read More: http://thyroid.about.com/b/2010/12/20/big-head-thyroid-cancer-risk.htm
