Hyperthyroidism affects up to 2% of women in the UK and the US and is ten times more common in women than men. In regions with normal levels of iodine, hyperthyroidism is caused by Graves’ disease in 60-80% of cases. In regions with iodine insufficiency toxic nodular disease (caused by toxic adenomas) accounts for 50% of cases of hyperthyroidism and this aetiology is more common in older people. Patients with hyperthyroidism should be referred. Overt hypothyroidism is present in 0.2-5% of the population and is more common in women and with advancing age. It is usually managed in primary care and rarely requires referral.