I agree with JJ. I have noticed that female doctors are, almost without exception, very friendly and engaging with me. That certainly helps the overall medical experience in many ways, and particularly with the genital and DRE exams, or any exam that involves nudity.
That said, I have certainly had an immediately sexual reaction to two of my female MDs. I mean I got and held an immediate and quite upright and rigid erection (this happened when I was in my late 50s and early 60s!). One in particular was young and attractive with the type of body that I really like -- lean and athletic, with graceful movement and a nice full ass. She had great bones, as they say, a very pretty face and hair but almost devoid of make up. In other words if anything she was dressing down, not up. That exam involved a full skin check (for Lyme disease) so I was naked when I had the boner. I am not a shy person but in that case I was so obviously erect (and without intending to brag I do have a large penis) that I was self-conscious about my condition. She, by the way, did nothing but smile, a beautiful smile that only made me harder.
That was a memorable exam. I had another one that really turned me on from another beautiful woman, this time well dressed and made up, though quite slim and demure. She too merely smiled when she noticed.
On the negative side, I had an exam by an not very attractive NP who was also pregnant. This involved a rash on my penis, so she had to touch it. I tend to get at least a partial erection when a female clinician pays attention to or touches my genitals, but in this case I got none.
So I do think attractiveness changes or at least affects the experience. But the attractiveness in my case is not to a drop-dead gorgeous woman, a woman who is beautiful in the Hollywood sense, but rather one who has that magnetic quality (perhaps specially for me) as well as above average good looks. In the end, hotness is in the eye of the beholder.
Good question by the way. I have thought quite a bit about why I respond so much to some doctors. I always get an erection when examined by my PCP, an attractive woman in her early 40s, but it is not what I would call a raging erection, merely a full penis with some stiffness -- the type that in the right circumstances could be stroked so as to suffice for a satisfying sexual experience. But she is not particularly attractive, just slightly above average lets say, and not overweight at all. And very, very friendly and pleasant, plus highly communicative (something which, thank goodness, turns me on).