Some men with NAFLD have low serum levels of testosterone (male hormone). Often, levels are only slightly low and do not cause symptoms. However there are several reasons to think that these low levels may be aggravating the liver disease. NAFLD is thought to be caused by resistance of tissues to the actions of the hormone insulin (Insulin Resistance or IR). Low testosterone levels may cause IR. Treatments for prostatic cancer which lower testosterone levels result in both IR and in NAFLD. Mice who cannot produce testosterone also develop NAFLD and this is reversed by testosterone replacement.