Human growth hormone

Human growth hormone: What is it?

It's a microscopic protein substance that is secreted in short pulses during the first hours of sleep and in response to stress. It is made throughout a person's lifetime, but is more plentiful during youth.

It stimulates growth in children and plays an important role in adult metabolism. It was first isolated in 1956 and its structure was identified in 1972.

Before the advent of genetic engineering, the only source of HGH was from human sources. The pituitary glands were removed from corpses, processed and the resultant hormone extract injected into people who were growth hormone deficient.

Why is it used?

Human growth hormone (HGH) has been helping growth hormone deficient children in the UK to grow normally since 1959. But concerns about the transmission of CJD mean that all supplies of HGH are now manufactured using artificial techniques.

In 1959, reduced height children were given HGH to help them grow. Without treatment, some boys would only grow to a height of around 130cm by the age of 18. With HGH they could reach a height close to the normal of just over 180cm. It was hailed at the time as a great medical breakthrough.

HGH has found a wide range of other uses now that it can be synthesised in unlimited quantities in the laboratory. It is used, for example, to reverse muscle wasting in AIDS patients, but without any major health benefits. This has led many athletes to consider using the hormone as a performance-enhancer, increasing their muscle size and strength. Modern research has cast doubts as to whether there is any objective improvement in performance. Because of the importance of the HGH to the body's biochemistry, HGH has also been promoted as an anti-ageing treatment. Many of the claims made for HGH have a doubtful scientific basis.

What are the risks?

Elevated levels of HGH due to benign tumours of the pituitary gland lead to swelling of the soft tissues in the body; abnormal growth of the hands, feet and face; high blood pressure and an increased tendency to sweat with excessive hair growth, a condition known as acromegaly. Injections of HGH without any underlying deficiency may cause diabetes.

What about CJD?

Creutzfeld-Jakob Disease is a side effect of the HGH that was made from the pituitary glands of humans. The infective agent which causes CJD resides in the brain, and using HGH in live patients ran the risk of passing on the agent. CJD has an incubation period of up to 30 years. Natural human-derived growth hormone has not been used anywhere in the world since 1985, when the synthetic hormone was first identified.

Between 1985 and 2003, 26 cases of CJD were identified in adults who had received human growth hormone, as children, before 1977, in the US, out of a total of 7700.

As a result, those who have received treatment may not know their fate for a long time. In scientific circles, it was clear as early as 1977 that there was a risk of transmission. This date has now become the determining factor in who can claim for compensation.

Synthetic HGH is clear of the infective agent that causes CJD.

Dr Jeni Worden last medically reviewed this article in January 2010.