Medications for PCOS include oral contraceptives and metformin. The oral contraceptives increase sex hormone binding globulin production, which increases binding of free testosterone. This reduces the symptoms of hirsutism caused by high testosterone and regulates return to normal menstrual periods. Metformin is a medication commonly used in type 2 diabetes mellitus to reduce insulin resistance, and is used off label (in the UK, US, AU and EU) to treat insulin resistance seen in PCOS. In many cases, metformin also supports ovarian function and return to normal ovulation. Spironolactone can be used for its antiandrogenic effects, and the topical cream eflornithine can be used to reduce facial hair. A newer insulin resistance medication class, the thiazolidinediones (glitazones), have shown equivalent efficacy to metformin, but metformin has a more favorable side effect profile. The United Kingdom's National Institute for Health and Clinical Excellence recommended in 2004 that women with PCOS and a body mass index above 25 be given metformin when other therapy has failed to produce results. Metformin may not be effective in every type of PCOS, and therefore there is some disagreement about whether it should be used as a general first line therapy. In addition to this, metformin is associated with several unpleasant side effects: including abdominal pain, metallic taste in the mouth, diarrhoea and vomiting. The use of statins in the management of underlying metabolic syndrome remains unclear.