• Growth hormone should never be stimulated in people who have not completed their growing phase (unless under medical supervision).

• If excessive growth hormone is released skin may become coarse. This will be reversed and normalized when such stimulation ceases.

• Joint enlargement is possible if growth hormone stimulation continues for an excessive amount of time, and so a programme of several months use followed by several months non-use is suggested.

• It is suggested that any use of amino acids in this way be accompanied by a dietary strategy which increases antioxidant levels (see Chapter 8).

Is there a 'death' hormone?
I have shown the power on health and 'youth' of growth hormone produced by the pituitary gland, and I have suggested that it does not seem to influence life expectancy. But some researchers take the view that with ageing the pituitary may start to produce a 'death hormone'. The evidence for this lies in unpleasant experiments in which rats and other animals have their pituitary gland removed so that effects can be observed. This is known as a hypophysectomy, and it is an operation performed on some people with cancer in order to slow down progression of their disease. When this operation is done experimentally the ageing process is seen to slow down. There is less cross-linking of tissues such as collagen, less chronic disease of ageing and a long list of 'improvements', all suggesting that ageing is being slowed.

However, as Weindruch and Walford report: 'Although these animals show features of greater youthfulness, they do not enjoy an extended species-specific maximum life span.' It may be that rather than production of a 'death hormone' being prevented by removal of the pituitary, what is actually being prevented is the circulation of 'faulty' hormones, such as a large molecule growth hormone which is often noted in elderly animals. It is believed that these have their harmful effect by blocking receptor sites, thus preventing 'real' growth hormone from being able to act.

In effect, whether the pituitary produces death hormones or faulty hormones which act like death hormones, the fact remains that it can be seen to be involved in the ageing process in a direct way. What is of particular importance to us is the fact that dietary restriction has influences on the pituitary similar to those in hypophysectomy. Dietary restriction, it is suggested, may therefore act in much the same way as an hypophysectomy.

However, this is an incomplete comparison, with only some features of dietary restriction effects being the same as removal of the pituitary. For one thing, life extension is not produced when this gland is removed, and for another the effects on levels of growth hormone are not the same. When an animal no longer has its pituitary it cannot produce growth hormone in anything like previous quantities. But on long-term dietary restriction, growth hormone might continue to be produced, although experimental results to date are confusing. In fasting (short-term dietary restriction) growth hormone production certainly is increased.

From an evolutionary viewpoint it is worth considering that there would be nothing to be gained by an organism (animal or human) investing valuable energy in producing a hormone which is designed to make it grow during a period of extreme food shortage. A further interesting observation is that when animals have their pituitary gland removed they automatically start to eat at a level similar to that applied during dietary restriction. In this instance it makes evolutionary sense for the animal which is no longer producing growth hormone to automatically require less nutrition, since its growth and repair mechanisms will be somewhat reduced in their need for raw materials.