Leigh,

My son was in a similar situation as yours...diagnosed at the age of 6 1/2, with a 13 yo bone age. He has been taking Lupron injections since shortly after diagnosis...so for over 6 years now. I expect that we will keep him on the Lupron for another year maybe, then let Nature take its course. Re. your question about the differences between Lupron and Letrozole:

Basically, Letrozole, Arimidex, and Femara are all drugs known as aromatase inhibitors. Lupron is a type of drug known as a GnRH agonist. In treatment of CAH, they work towards the same goal...slowing down bone age advancement...but they go about it in slightly different ways.

As you know, bone age advances when there are high levels of "estrogen." In the adrenal glands, estrogen is made from androstenedione and testosterone. So, if there are high levels of estrogen in a boy, you generally first have to have high levels of androstenedione and testosterone.

This is where the difference between GnRH agonists (Lupron) and aromatase inhibitors (Letrozole) comes in:

Lupron works by reducing the amount of testosterone that is produced. If there are low levels of testosterone, then there will be low levels of estrogen. Letrozole does NOT reduce the amount of testosterone...it just stops testosterone from being CONVERTED to estrogen. Therefore...if you are on Lupron, you would have low levels of estrogen AND low levels of testosterone. But, if you are on Letrozole, you could have low levels of estrogen, but HIGH levels of testosterone.

So, which is "preferable?" As always, there are pros and cons to both...

The up-side to Lupron is that it has been around for a while and is generally considered to be effective and safe. The downside is that, when it slows down bone age advancement, it can also dramatically slow down growth rate. (High levels of andro and T cause bone age advancement, but we also need them to grow...unfortunately, it’s one of those catch-22 situations with CAH.) So, if the ONLY reason for using Lupron is improving final height, you may not necessarily come out ahead in the end...in general, the younger you start, and the longer you are on Lupron, the greater the amount of height gain.

I think the slow-growth issue is one of the reasons why doctors are exploring other alternatives for slowing down bone age, like aromatase inhibitors. By allowing androstenedione and testosterone levels to remain high, growth rate should be normal. But, by keeping the andro and T from being converted to estrogen, then bone age advancement should not be a problem....in theory, a win-win situation.

The down-side (and,unfortunately, there always seems to be a down-side...I guess nothing is for free!), aromatase inhibitors have not been around that long. So, long-term side effects are still unknown.

My son’s endo considered switching my son to Arimidex several years ago. At the time, I remember thinking that it was like a miracle come true....being able to keep his growth plates open, while allowing normal rates of growth. But, eventually, we scrapped the idea, mostly because we considered the drug to be too new and untested. Our doctor also looked into Tamoxifen, which is another drug that blocks estrogen, but works in a different way yet than either Lupron or Arimidex. We gave that up too, for the same reason.....not enough long-term data about safety.

That was several years ago, though, so there may be new studies out. I would certainly ask your endo, so you know more of the pros and cons. Good luck, whatever you decide.