A link had never been established between the growth hormone and the patient’s immune system. Scientists then discovered that, in rodents, growth hormone and growth factor were linked to type 1 insulin (IGF-1). The increase in thymic mass and thymopoiesis depends upon IGF-1. In 2008, a team of researchers at the University of San Fransisco showed that injection of very high levels of growth hormones in patients infected with the AIDS virus also increased the mass and function of the thymus.

To further develop these new findings and to find out more about the link between growth hormone and the production of lymphocytes, Gabriel Morrhaye, Dr Hamid Kermani, Dr Henri Martens and Professor Vincent Green pooled their efforts. Together, they studied thymic function in men and women between the ages of 27 and 69 presenting with a lack of growth hormone and who were treated with a daily injection of this hormone. The study took place in three stages: measurement of the biological parameters during the growth hormone treatment, one month after stopping this treatment and finally one month after treatment was reintroduced. At each stage, patients’ blood samples allowed the researchers to measure the TRECs, which reflect thymic activity.