Zeranol is approved for use as a growth promoter in livestock, including beef cattle, under the brand name Ralgro (by Merck Animal Health) in the United States. In Canada, it is approved for use in beef cattle only. Its application is not approved for use in the European Union. However, it is marketed under the brand name Ralone in Spain.
Although zeranol may increase cancer cell proliferation in already existing breast cancer, dietary exposure from the use of zeranol-containing implants in cattle is insignificant by some scholars. Zeranol may be found as a contaminant in fungus-infected crops. It is 3 to 4 times more potent as an estrogen than the related compound zearalenone.
^Xu P, Ye W, Jen R, Lin SH, Kuo CT, Lin YC (November 2009). "Mitogenic activity of zeranol in human breast cancer cells is enhanced by leptin and suppressed by gossypol". Anticancer Research. 29 (11): 4621–8. PMID20032412.