Read about Blast and cruise. That is what I do. I am 40 and do this. I have low natural test levels so I have to take TRT at 100mg a week. This is my "cruise" dose and I maintain my gains after my 12 week blast. I need it because I'm not producing enough naturally.
Now, a "blast" dose would be 500mg a week and is like a cycle for 12 weeks. You obviously see the normal growth like any cycle.
I hope this is helpful. There are many guys on here doing blast and cruise. You will find tons of info on here about it.
I'll say this, I'm on TRT because when I was younger I didn't cycle correctly and didn't do PCT so I put myself in this position. Research a lot before you do anything. Good luck.