Hi, I'm Nick. I've always been a thin guy. As a kid and teenager I was super skinny and even now I still definitely have a thin build. I'm between 120-125 usually and am 5'7''. This is just what I'm used to and I don't want it to change. I'd like to go on T and have my face change and everything but I don't want to get too thick and bulky. Is there anyway or indicators to tell how my frame will change? I'm 25, have a high metabolism, active life style and eat a diet of mostly veggies and fish. Some pea protein powder and nuts and fruit in moderation. No dairy, eggs, land meat, processed sugar or gluten. My dad was very thin during puberty and still is thin. He's got a bit of a beer belly but he's nearing 60, doesn't work out much and drinks beer regularly (I also don't drink). I am hoping my frame doesn't change much. I'd like my face to masculinize and voice to drop and wouldn't mind some facial and body hair.

At you age, your bone growth should have ended a long time ago. Women's bone growth ends early because of the estrogen shutting it down where as i found I was still growing (though slow) into college. You might put on muscle mass with the amount determined by your workout and genetics. As for the beer belly, you already know about that.
Facial hair depends on your genetics as well. I didn't start female hormones until I was 25 and I only had a light beard and no body hair on my neck, chest or back. This was something my dad gave me because my mothers side of the family was hairy. The voice should drop to the male range but exactly how far down is guess work.
There is also one other interesting fact. I went swimming a while after I transition and I found I floated like a cork. The reason was weigh I gain and the conversion of muscle mass to fat. Going the other way, you may find some of your fat become muscle without altering your physical size.

Thank you Dena, I love all your replies. They are very helpful. I am hoping I don't get a beer belly. I do some core exercises and plan on increasing those and I do eat a pretty healthy diet that is very low fat. I'm a bread free vegan except for the occasional fish and rarely eat processed foods. I don't care about facial hair. Wouldn't bother me if I got any but I know I probably will but I think I will probably choose to shave it everyday if I do. I kinda hope I get a hairy chest like my dad so it would cover up my chest surgery scares if I'm lucky. But I have very fair blond hair so I don't know if that's realistic. I guess time will tell.

Adding more muscle in key places will alter your skeletal-musculature somewhat. By adding muscle-mass, you'll be able to develop a more triangular figure. And while your bones are unlikely to grow any more, your tendons and ligaments may pull your frame into a more rigid and less flexible stature. It's possible you may gain an inch height from this, although it's mostly just standing straighter than was comfortable before.


     Hugs,
- Katie
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Your frame will not change much beyond adding muscle in places, making a more V shape if you work out your upper body. The bones are set where they are, so no major frame changes. It's mostly just fat and muscle changing, and it sounds like there isn't much of fat to change for you, so the changes will be almost entirely muscle. I think you would only end up thicker if you were specifically working out to bulk.