As an adult there are things that stay relatively the same, constants if you will. We are told that as we age, we grow when we're young and then proceed to shrink until we die. Sure our weight fluctuates, even our shoe size as our feet flatten out with age, but our height is one of those things that is supposed to stay relatively constant for a good 30-40 years.
Beyond the abnormal things that can radically change your height once it has been established as a young adult, such as a cosmic particle mutating your pituitary gland or losing your legs, the only thing one should expect is to shrink as the cartilage compresses between your vertebrae.
Recently I had a basic physical done for some life insurance changeover and I was surprised to find that I'm actually an inch taller than I thought I was. For my entire life I have always thought I was six foot two inches tall. It's on my driver's license. When asked your height on a form I always put 6'2". It's one of those things. But when they measured me with my shoes on I was 6'4". I couldn't believe that the heels on my shoes were two inches tall so we measured with them off. I had them do it three times, with different people. I'm officially six foot three inches tall.
The universe continues to amaze me.