A very interesting shailo that is l’maseh…
There is a boy that unfortunately has to perform a chalitza. He is 13 years old and lacking simanei gadlas (shtei sairos). The shailo was asked if he is allowed to have some sort of hormonal treatment (an injection, pill, whatever it might be) to speed up the process that his shtei sairos should grow up quicker.
The answer to this will apparently depend on how the hormonal treatment works.
The idea of the sa’aros is that they indicate physical maturity (sexual function). If sa’aros are induced by hormonal so that a boy has hairs, yet does not have physical maturity, then the hormonal treatment will not (apparently) make him into a “gadol.”
However, if the hormonal treatment only speeds up the natural process of maturing into an adult, and the appearance of hair will be a true indication of actual physical maturity, there will (apparently) be no problem in inducing the maturity by means of hormonal treatment.
This issue should be verified through consultation with experts.
If he is already thirteen, then even as a natural process, the sa’aros shouldn’t be too long in coming, but there is no guarantee, and ages for the appearance of sa’aros do vary.
In a practical sense, the rabbis involved in the chalitza process should of course be consulted.