I got a Dutasteride presciption that I take daily since the beginning of my HRT. I don't really have a basis for comparison of its effects since I've always been on it. However I can say I have definitely experienced significant hairline regrowth, and I continue to notice improvement.
At the start, I had lost about 3/4" of hairline at the corners, and a little in the center. I did not expect this to regrow at all, but after about 3 months I noticed some unusually thick peach fuzz in this area, much larger and longer than normal head fuzz. That fuzz continues to be present, and over the months has VERY slowly grown into normal hair from the back forwards. Now, about 1.2 years into the process, I've regained about half of what I had lost. The changes are very, very slow but I believe it is continuing to progress to this day.
Judging from the distribution of thick fuzz, I do not believe this will completely feminize my hairline. But I do believe I can now get away with a very small number of hair follicle grafts and call it good, as my body will likely fill in around it with shorter regrown hairs.
Since the vast majority of HRT regimens do not appear to include a 5AR inhibitor, and the predominant wisdom states that hairlines should not be expected to regrow at all - I can only assume that these results can be attributed to my Dutasteride. Not exactly a scientific result, but good anecdotal evidence that seems to mesh with others on this thread. 🙂