I am not a researcher in this area, but after some Internet searching my general impression as a medical doctor is that such a hormone has not been explicitly identified. I suspect you are looking for information on oxytocin, with perhaps an interest in vasopressin as well. In clinical practice oxytocin is of interest during the management of arrested labor, but it also has effects during sexual arousal and climax. It also controls some aspects of lactation. Oxytocin is released during sexual arousal and I have seen websites hyping oxytocin as a cure for inhibited sexual desire. Whether it "regulates" or "controls" sexuality seems unlikely. It seems that oxytocin could be the effect rather than being the cause.
A lot of the speculation about oxytocin function comes from experiments on other species. The two species I have seen described are mice and voles.
When scientists "knock out" the oxytocin mechanism by genetically engineering male and female mice to be deficient in oxytocin, the mice do not display differences in their sexual behavior. See this 1996 paper from the Proceedings of the National Academy of Sciences.
It would be more accurate to say that oxytocin may participate in sexual processes, but more likely it's the cortical brain activity (the "higher functions") that are the main sources of control. Many people have stated that the brain is the primary sex organ. This, of course, means that if a person buys an oxytocin-labeled product with the hopes (or perhaps hypes) that it will make them or their partner more sexy, then sexiness is more likely to arise....or is that arouse?
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