Professor Jonathan Seckl
University of Edinburgh

Professor Seckl described the Pituitary gland as the 'conductor of an orchestra playing music written by the Hypothalamus', and Growth hormone (GH) as the body's most enigmatic hormone.

After being secreted by the pituitary, GH works on many receptors, but predominantly those in the liver, where it produces Insulin-like Growth Factor-1 (IGF-1). This is essential in childhood, but is not thought to play such a key role in adults. GH deficiency in adult patients with pituitary disease leads to muscle loss, central obesity, fatigue, Osteoporosis, heart disease, depression and a generally poor quality of life. These symptoms have become better recognised in the last 10 years.

GH replacement (GHR) can change a patient from a 'sumo wrestler' to a 'Greek Adonis', by increasing muscle mass and reducing fat. However, there is great debate over whether this lasts after 2-3 years of treatment. GHR also increases bone density by up to 10% in 1-2 years, but there are doubts over whether this is beneficial, as GHR only strengthens the rim of the bone and not the internal trellis; other osteoporosis drugs are available that do not require a daily injection. The performance of the cardiovascular system improves with GHR, and cholesterol levels are reduced. However, treatment also raises blood insulin levels, which may increase the risk of heart disease, and the net outcome for the heart is not yet known. The effects of GHR on depression and anxiety have been studied by several groups, with inconclusive results.

To receive GHR, a patient must have a known pituitary disease, with at least one other hormone deficiency, and an inadequate response to two stimulation tests: usually an insulin stress test and one other. GHR is administered by injecting synthetic hormone under the skin every day, usually at night. The dose is adjusted by monitoring blood test results (IGF-1 levels) and side-effects. Reassessment follows a 6-month trial; only then is long-term treatment decided. The side-effects of GHR include oedema, fluid retention, joint and muscle pain, and, less commonly, raised blood pressure and Hypothyroidism. Anyone who is receiving GHR should be carefully monitored using IGF-1 and fat measurements, bone density scans and ECGs. The most difficult problem is funding GHR; it is very expensive, available patchily, and local rules differ with regard to prescribing.

Professor Seckl said that GHR had many 'don't knows', and that it was still a new and contentious subject amongst medics. He claimed to be agnostic, and felt that there was not yet enough convincing long-term research on GHR to turn him into a 'believer'. Worldwide trials are currently taking place, and the results will be published in the next 2 years. Then the medical world should have some answers, and be able to rely on proof - not hopes...