Testosterone Replacement in Non-alcoholic Steatohepatitis (TEREPINS)

20-35% of adults have non-alcoholic fatty liver disease (NAFLD), which often leads to liver inflammation and damage and sometimes to cirrhosis, liver failure and liver cancer; it is now a common indication for liver transplantation in the UK. No medical treatment has been shown to be effective in preventing its progression. 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. The investigators therefore speculate that testosterone replacement in men with NAFLD and low blood testosterone levels will reduce liver fat. Investigators will study 10 men with NAFLD and some inflammation or scarring (proven on liver biopsy performed for clinical diagnosis) and who have mildly reduced testosterone levels. Investigators will see if giving a 12 month course of Testosterone Replacement Therapy (TRT) to these men will lessen the severity of their liver damage. Consented patients will be seen after 6, 18, 30, 42 and 52 weeks. Patients will undergo a baseline clinical assessment, blood tests, an ultra sound scan, magnetic resonance scanning of the liver (to estimate liver fat), and a repeat liver biopsy to end the study. Patients will complete questionnaires, and undergo clinical assessment, blood tests, an ultrasound scan, and magnetic resonance (MR) scanning of the liver (to estimate liver fat) at baseline. Patients will have clinical assessments and blood tests at 6-weekly intervals for 12 months. At 12 months patients will have a repeat liver biopsy, ultrasound and MR scan.