What is the name of doctors that specialise in fixing human organs?

Question

what is the name of doctors that specialise in fixing human organs only?

Answer 1

It depends on the organ, as well as what "needs fixing."  A surgeon, for example, focuses on invasive procedures; and within that specialty, one can sub-specialize in surgery of a particular organ or system (i.e. cardiothoracic surgeon).  A gynecologist focuses on the female reproductive system.  A subspeciality in the field of gynecology would be reproductive endocrinology - the study of reproductive hormones (i.e. estrogen).  Hope that helps.

Answer 2

As momdoc answered, it depends on the organ in question. Are you thinking more broadly of an internist?