Doctors may be able to stave off HIV by giving patients growth hormone, researchers have found.

A team from the Gladstone Institute of Virology and Immunology at the University of California San Francisco said the hormone could stimulate the production of immune cells and help the body fight the infection.

The specific immune cells they looked at , T cells which are produced by the thymus gland, are attacked and destroyed by HIV, leaving patients unable to fight off infections linked to Aids.

In the study five male HIV patients were given daily doses of growth hormone.

After six months, researchers found the number of new T cells circulating in the blood had increased significantly.

The researchers say this is the first study to show how the thymus functions can be significantly enhanced by growth hormone therapy to stimulate it to produce new T cells.

However, they admit the study was small and the therapy is not yet ready to be given to patients with HIV.

Two of the five also experienced side effects from the therapy.

Potential adverse effects of the treatment include bone pain and abnormal bone growth, swelling in the arms and legs, carpal tunnel syndrome and even diabetes.

Doctors added that the study was only preliminary, and was not intended to show whether growth hormone actually improved the health status of the patients.

Larger trial

A larger study is planned to compare HIV-infected patients taking growth hormone with others not on the treatment.

Dr Laura Napolitano, who led the study, said: "Finding a way to stimulate the thymus to produce T cells would help HIV-infected patients to preserve and restore their embattled immune systems."

She added: "The results of the current study are preliminary, but give us hope that we may be able to provide therapies to stimulate thymic function and T-cell production in individuals infected with HIV.

"Additional studies need to be completed before we can conclude that growth hormone therapy provides benefit to the immune system of HIV-infected patients.

"We need to establish that the benefits of therapy outweigh the risks."

Early days

Dr Antonio Pires of Imperial College London, who, alongside Dr Nesrina Imami, has also carried out research into using growth hormone in HIV patients, told BBC News Online: "From our research we have seen that daily administration of 4mg of growth hormone induced HIV-1-specific T cell responses."

He said the changes seen were significant. "These effects disappeared with a decrease in the frequency of dosing."

He added: "These are promising data. However caution and more research is needed in order to ascertain the true benefits of growth hormone for the treatment of HIV infection."

Derek Bodell, chief executive of the National Aids Trust (NAT), said: "We welcome the finding that growth hormone may stimulate production of T cells to boost the body's ability to fight HIV.

"It is important to ensure that the use of growth hormone in any treatment does not have an adverse effect on the health of those who might receive the treatment."

He added: "The study clearly has a long way to go before we know if it can be beneficial for people with HIV.

"Of course with more than 40m people worldwide now living with HIV - and 5m diagnoses alone in the last year - it remains vital, in responding to the AIDS epidemic, that we look at all new opportunities to defeat the disease. This may come in the form of a variety of new treatments or vaccines."

The study was published in the journal Aids.