Dozens of former NFL players will be administered human growth hormone as the NFL and its players union try to determine the impact of use on players' HGH levels three people with knowledge of the plan told USA TODAY Sports on Wednesday.

The people spoke on the condition of anonymity because the study has not been announced publicly.

The tentative plan is for roughly 100 former players to participate in the study with two-thirds receiving HGH and the other third receiving a placebo. Their HGH levels will be measured before and after the trial.

It's part of the scientific design of the population study that will include blood draws from all current players to determine the so-called decision limit — i.e. the highest HGH level a player can have without facing discipline under the new performance-enhancing drug policy that is still being finalized the people said.

Current Minnesota Vikings players were informed of the plan Wednesday during a visit from their designated advocates from the NFL Players Association Martin Bayless and Ernie Conwell.

It was unclear whether any ex-players had agreed to participate in the study when the HGH would be administered or how prescriptions would be obtained for the drug.

Human growth hormone is naturally produced by the body stimulating cell reproduction and regeneration. It also can be administered artificially and is banned by most international sports organizations as a performance-enhancing drug.