A mitogenic agent in corncob bedding and fresh corn products disrupts sexual behavior and estrous cyclicity in rats. The mitogenic activity resides in an isomeric mixture of linoleic acid derivatives with a tetrahydrofuran ring and two hydroxyl groups (THF-diols) that include 9, (12)-oxy-10,13-dihydroxystearic acid and 10, (13)-oxy-9,12-dihydroxystearic acid. Synthetic THF-diols stimulated breast cancer cell proliferation in vitro and disrupted the estrous cycle in female rats at oral doses of similar to0.30 mg/kg body weight/day. Exposure to THF-diols may disrupt endocrine function in experimental animals at doses similar to200 times lower than classical phytoestrogens, promote proliferation of breast or prostate cancer, and adversely affect human health. (C) 2002 Elsevier Science (USA).