My son is 2 and he is also being monitored for growth. We saw the pediatric endocronoligist today as a matter of fact, although in our case the concern has been that he might require growth hormones.
I am with you in that the idea of giving medications to my child is less then an ideal situation. Unfortunately, every single medication in existence has potential side effects. They can also do a lot of good. For me, it's all risk vs. benefit. I guess my suggestion would be to first get a complete and total understanding of what precocious puberty means in terms of his long term health and happiness. Gain a full knowledge and understanding of what this may mean for him untreated. Weigh that against the potential side effects of Lupron. I would also be asking what (if any) alternative options are and research those as well. I also think it's important as well to not only know what the potential side effects are, but how likely they are (meds all seem to come with those stats as well). Then, once all of this has been done, make your decision. And to be honest with you, when it comes to any long term treatment using drugs, I am big on second opinions.
Good luck with your decision, and whatever you decide, I wish you and your son well.
There seem to be many side effects involved with the use of Lupron I have found 2 links here with more information www.lupronped.com?questions/default.aspx and www.lupron.com/