Lupron may be good. But its also cost prohibitive, and it is an unusual tact in HRT, and is not completely proven in TS HRT. While there is differant routes to take with HRT, it almost always involves spiro. This is the first I have ever heard anybody on Lupron.
Like it was stated earlier, Lupron also blocks estrogen, something spiro does not do. It would hurt one of the side benefits to Dutasteride, which is the fact when you block DHT production, it blocks a viralizing aspect of DHT, the reduced production of estradiol being one of the viralizing aspects of DHT (its a reason why breast growth is a side effect of Dutasteride).
On top of that there is the fact that spiro blocks DHT receptors.
While Lupron may block T itself more effectively, there are benfits to spiro that are not necessarily there with Lupron. Lupron does amount to chemical castration which may lower estrogen doses, it also poses some negative aspects with regards to feminizing the body. I am surprised the endo is going this route because of the cost involved. If anything is usually injectible, its usually delestrogen, which is relatively inexpensive and very effective when taken with spiro at reducing T.