Acromegaly is a rare endocrine disorder that most commonly results from an adenoma, a benign tumour of the pituitary gland that secretes excessive growth hormone (GH) and leads to excess production of the hormone IGF-1. A common criterion for the successful treatment of acromegaly is normalisation of IGF-1 levels, since reduction of excess IGF-1 correlates closely with relief of clinical symptoms. The progression of acromegaly is typically slow, and acromegaly often is not clinically diagnosed for 10 years or more. As the disease advances, patients typically exhibit abnormal growth throughout the body. Acromegaly most commonly affects middle-aged patients with the mean age of onset being 40 to 45 years. The symptoms associated with acromegaly typically include the effects seen with growth hormone over-production. In some instances, the tumour compressing and injuring the normal pituitary gland and optic nerves also causes symptoms. Untreated acromegaly results in marked bone and soft tissue changes including altered facial appearance, enlargement of the hands and feet, sleep apnoea, and carpal tunnel syndrome. More serious problems may include accelerated cardiovascular disease, hypertension, diabetes mellitus and possibly an increased risk of colon cancer. If the tumour develops before bone growth is completed in adolescence, the result will be gigantism. Because of the serious systemic changes resulting from growth hormone excess, treatment is essential, typically with surgery. However, a significant number cases, surgery is either not appropriate or not effective. In these patients, a somatostatin analogue is typically used. These mimic the effects of somatostatin, a hormone produced by the hypothalamus and some other tissues such as the pancreas and the gastrointestinal tract. Somatostatin inhibits the release of growth hormone from the pituitary gland. However, it also inhibits the release of insulin and glucagon from the pancreas, which is why somatostatin analogues, which retain these peripheral activities, are also associated with causing diabetes.