To explore the impact of the drugs, the researchers plan to start one group on the treatment straight away and another group 12 months later. The children in these groups will be chosen randomly.
The KCL researchers said there would be no minimum age for taking the drugs, but puberty normally starts around the age of 11 for girls and 12 for boys.
The trial will look at issues such as bone density, brain development and mental health and wellbeing over time.
The research team said the trial had been given ethical approval and was expected to start in January, with five to six children recruited every month. The first results should be available in around four years.