"The doctor had already answered that question."
Translation:Ο γιατρός είχε απαντήσει ήδη σε εκείνη την ερώτηση.
The profession is γιατρός for both genders. There's a specific feminine version, γιατρίνα, but it comes from a time when women doctors were few so use it at your own risk. ;)
There are many feminine and neuter words that end in -ος, it's not a masculine ending only, don't let it confuse you. :)