Hi doctor are men most get taller after 20 years old about 2 or 3 cm???

Rare to grow at 20: Most men stop growing around age 18- but occasionally some will grow until age 21 or so, but if so, not much more. Taking measures to increase your production of growth hormone might help, but if your growth plates have closed (like most 19 yo's) then you've reached your max. See "http://www.thebodywellusa.com/blog/dr-mike-carraghers-top-10-ways-to-increase-your-human-growth-hormone-hgh-levels".

Accept your height: Some kids continue to grow taller into their late teens or rarely early twenties but only when their bone maturity lags behind their age. If the growth centers of the long bones have fused, you cannot grow taller. A single x-ray of the wrist ; hand can yield a bone maturity.Most boys stop at 17. When you have reached bony maturity, you are done.