Dr Peter Trainer
Christie Hospital, Manchester

Acromegaly is virtually always caused by a benign (non-cancerous) tumour of the Pituitary gland; this results in excess secretion of Growth hormone (GH) and Insulin-like Growth Factor-1 (IGF-1). There are approximately three to four new cases per million each year. GH is normally released into the bloodstream in waves, whereas in acromegaly it is constantly present. IGF-1 is a protein found in the body and is a marker for GH activity.

Acromegaly is relatively easy to diagnose. MRI scanning is an accurate method of detecting pituitary tumours. Blood tests include the oral glucose tolerance test, and measuring random GH and IGF-1 levels. In 75% of patients there is a correlation between raised GH and IGF-1, so it is important to measure both.

The clinical features of acromegaly are many and varied. There is often a slow coarsening of facial features (nose, lips, tongue and lower jaw). The hands and feet become broader. Excess sweating, muscle weakness and acne are common. Compression effects of the tumour can cause headaches and visual disturbances. Sleep apnoea is a dangerous symptom, since irregular breathing during sleep leads to low levels of oxygen in the blood. This results in headaches, especially in the morning, and tiredness. Diabetes mellitus is a well recognised complication of acromegaly; 20% of patients have diabetes, though most do not require insulin injections.

What causes acromegaly? There appears to be no proven evidence for environmental or traumatic causes. It is rarely inherited; the inherited version is characterised by easily recognised features shared within families.

Why does acromegaly need treatment? Initially to control symptoms. However, more importantly, long-term excess GH can reduce life expectancy, so there is a need to lower GH to a normal level. Additionally, the tumour can compress the normal part of the pituitary, resulting in a deficiency of other hormones (hypopituitarism). The need to preserve optimum pituitary function is thus crucial.

First-line treatment is usually Transsphenoidal surgery. The outcome depends very much on tumour size - larger tumours have a lower success rate. Complications include Diabetes Insipidus and meningitis. However, the main problem is hypopituitarism, whereby the healthy part of the gland may be removed or damaged.

Radiotherapy is commonly used for patients whom surgery has not cured. A 5-week course of daily treatment aims to stop the cells dividing and reduce the tumour. The effect can, however, take 5 or 10 years to appear, and there is also the risk of hypopituitarism. A new form of radiotherapy called stereotactic radiotherapy or the 'gamma knife' is currently available in only a few centres. A single dose of radiotherapy is used, with the advantage of increased accuracy. It is most suitable for small tumours and in patients with residual tumour after conventional radiotherapy.

Drug treatment for acromegaly originally consisted of dopamine agonists, such as Bromocriptine, which only worked for some patients and had many side-effects. More recently, cabergoline has produced an improved response with fewer side-effects. Somatostatin analogues, given as injections, are successful in treating acromegaly by inhibiting the release of GH. Their side-effects include diarrhoea, abdominal pain, low blood sugar and gallstones. Pegvisomant is a new drug treatment which works in a unique way, by inactivating GH in the bloodstream. Current research on this product apparently is very promising. However, it will not be available in this country until mid-2001.

Finally, the question of an increased risk of colon cancer amongst acromegalics was raised. This is still under debate and, as there are currently no guidelines, not all patients are offered screening. Many units err on the side of caution and suggest that all acromegalics over the age of 40 should be screened every 3-5 years. A move towards national consensus guidelines is under way.