Homosexual orientation by choice
      This  study , led by  Alan Sanders  at Chicago's North Shore  University HealthSystem Research Institute, directly compared about 2,000 homosexual  and heterosexual men  in order to find genetic differences between them.      They didn't find much. The researchers picked up some signal near several genes  that are expressed in the brain. They also detected some genetic differences near the gene for the thyroid stimulating hormone receptor.       This gene plays a role in Graves' disease , a thyroid autoimmune disorder  that, according to a  recent Danish study , occurs more often in gay men . These and other related findings, write Sanders and his colleagues, "point to a possible connection between thyroid function  and sexual orientation  in men."       What can we take away from these modest results?  The study, as the authors recognize, is fairly small as far as modern genetic studies go, and so its power to find genes linked to same-sex difference...