I am 43 myself and I have found that if you use performance enhancing drugs it will help by giving you what you are missing. But it only works if your diet and training are right. You might want to have it all checked to see if you are on the right track. IMO diet is 80% of your success or failure in gaining mass. You can put on some good muscle, but like it was said, your days of looking like Lou are gone, but you can achieve good quality and respectable size. I know some pretty big 65 year olds who started pretty late. They are not the biggest bros but they are in great form with decent size.