What Causes Speech Delay In Kids?

i have a 2 1/2 yr old baby boy who is not talking any words yet, except for amma and very rarely he says appa.he is usually very hyperactive & restless,throws toys,keeps playing all day long,impatience to wait,loves to run from one room to another, less concentration,does no follow instructings,observes & learns on his own,eye contact is less when we try to make him sit and teach him,does not turn & look all the time whenever we call him by name....could these symptoms be just because of hyperactivity of the child or could there be any other reasons?pls advice..