Re: is it possible to grow taller after 21 years ?

The age at which a person stops growing vertically varies with the onset 
of puberty and the speed at which one grows vertically before puberty is 
governed primarily by growth hormone (sometimes called somatotropin).  If 
you have gone through puberty, which I assume you have since you ask about 
the age of 21, then vertical growth is over for you.  If GH is low then 
the speed of vertical growth is less than normal and if puberty comes 
early (sex hormones will cause closure of the epiphyseal plates where long-
bone growth occurs) the total height will be less that normal.  Once the 
epiphyseal plates close there can be no more growth.  Some individuals 
undergo surgery to lengthen the bones of the lower extremity but this is a 
very painful process and is also quite expensive.  I think you will have 
to start looking at all the wonderful benefits of being shorter than 
normal which is much easier to deal with, and much healthier, than being 
taller than normal.

As to growth hormone action, I answered a question on that topic several 
years ago and am attaching it for you to read below:  
The height a young person attains is due to growth within the long bones 
of the body.  This growth take place at the junction of the diaphysis 
(shaft) and the two epiphyses (tips) of the bone at a thin line of 
cartilage called the epiphyseal plate.  This plate ossifies (changes from 
cartilage to bone) in response to the sex steroids estradiol (in females) 
and testosterone (in males).  Once ossification occurs there can be no 
more length type growth.  However, the body still produces growth hormone 
(GH, also called somatotropic hormone), but normally at a lower level.  
This should be enough to maintain the body tissue without further growth.  
However, as a person ages, the level of GH may increase a minute amount 
which will stimulate the bones to grow slightly thicker and the soft 
tissues to also grow in volume over the years.  Have you ever noticed how 
grandma and grandpa usually have larger ears and noses and thicker fingers 
as they age?  In most cases this is so slow and slight a change that the 
only way to show that it is happening is to take pictures every year over 
a period of years and make precise measurements of the ear size and so 
forth.  Of course you could make direct physical measurements but many 
people would not really appreciate what you would be trying to accomplish 
and it also becomes difficult to get a measurement every year since people 
move or die and your population becomes smaller and smaller.  To get back 
to your question, if there is an anterior pituitary problem that results 
in an elevated GH level prior to puberty (before epiphyseal plate closure) 
then the person will get taller and wider than otherwise.  Gigantism is 
the name applied to this condition.  If the elevated GH level is post 
puberty, then the person just gets wider (thicker) without increase in 
stature.  Acromegaly is the name applied to this condition.