So I am a pure ectomorph. If I didn't start lifting at age 17 like I did (now 25 years old), I would probably be skinny fat with a gut, as I was 130 lbs @ 5'8 at the time.
Now I am around 195 lbs, still at 5'8, probably 14% bf. I have a naturally small frame (small/narrow bone structure). Since I am currently bulking, I find my joints (mainly shoulders) starting to get sore, and the theory is that once you have fully developed, you can continue to grow (gain muscle) however your bones and ligaments will not.
Therefore, if you don't have a big/thick frame, this extra mass can be pretty hard on your joints, bones and ligaments. Does any other ectomorphs have this issue? Is this perhaps why people are taking GH, as it helps strengthen joints and ligaments to allow them to handle the extra mass on a smaller frame?
I like the size I'm at, although I do like staying around 10% bf, but I obviously know it's nearly impossible to grow without putting on atleast some fat, so I will be cutting in the spring (slowly). I'm sure my joints will feel better after losing some unwanted fat, but I also don't want to experience pain at the size I'm at now, because honestly, I'm not that big especially comparison to the pros at my height who weigh in close to 300 lbs in the offseason.