As stated in the title: is there any evidence that the hormones etc that the body produces during intercourse increases one's likelihood of encountering a bear in the back-country?
There is at least one documented incident with a bear that occurred in the 1980s which may have been related sexual intercourses.
Unfortunately the two teenagers, Jane Ammerman and Kim Eberly, did not survive.
Stephen Herrero wrote about the incident in his book titled Bear Attacks: Their Causes and Avoidance:
When our investigating team visited the dump, we saw a horse carcass beginning to decay. Items such as this can attract bears from several miles away. Whether attracted by the dead horse or other garbage, the grizzly bear was probably heading to or from the dump in the early hours of july 24. Near his route of travel were the two teenagers, apparently sleeping on top of their tent because the night was warm and muggy. The bear had learned to accept the smell of humans from foraging at the dump. The bear might have approached the teenagers because of the odors from sexual intercourse, but whether this was the case and what happened next are conjecture.
In my opinion, there are other risk factors of bigger importance that I would try to address first.