Patience, plain and simple. I've been on HRT for almost two years and I am still losing muscle mass from my forearms and hands. I think it took almost a year before I noticed that the women's tops I bought during my pre HRT days were no longer so tight around the shoulders, and over a year before I noticed I had lost a size in women's t shirts. It takes time, and there may be a lot of night time and early morning aches and pains as well.
I recently decided to repurpose some of my old sport coats as boyfriend jackets. When I tried them on after two years of HRT they looked like clown coats. They are Brooks Brothers and worth the money to have reworked, and I just cannot find women's jackets in those colors and patterns. I had to have each one taken in on the waist and narrowed across the shoulders, as well as having them hemmed up an inch or so and having the sleeves reduced in diameter—and these were jackets that fit me well before HRT.
Believe me, you will lose male muscle. But it takes time.
