Building muscle with low t

I'm 40 and been hitting the gym for two years with the last year pretty hard,I was 195 and dieted down to 160 last year and been gaining slowly,I'm 172 now but fight fatigue pretty bad so I had a bunch of blood work done by my gp doc and had low t.I know there's a lot of other factors but my results were 195 on a scale of like 240-900.I don't have any other issues except being moody.I really don't want to get on t right now.Im want to put on 15-20 Lbs of muscle in the next few years and I think I work hard enough in the gym and my diet is spot on,I'm very dissaplined with it.
So my question is am I pissing in the wind or is it possable to reach my goals with issue.
Thanks guys