system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What in the body makes someone horny and what goes away when the sexual tension is released to turn off the feeling for a period of time?
gpt
In men, a hormone called prolactin increases after orgasm. This will cause a lack of interest in sex, difficulty in achieving an erection and orgasming. It is primarily responsible for the 'refractory period'. 

There is a prolactin lowering drug called cabergoline which can drastically reduce the refractory period and make some men multi-orgasmic.

Prolactin is also responsible for causing women to lactate.