Maybe "growth factor" as in "sunlight is a growth factor" is appropriately neutral?
Case in point, melanin synthesis and libido systems are related: There's a drug "bremelanotide" and by now probably some others, injectable melanocortin receptor agonists originally marketed for whole-body skin tanning. But actually it's marketed for libido enhancement and in the process it turned out that most MC receptor subtypes regulate mood/cognition more than skin color
TL;DR, there's evidence to suggest - in humans - that sunlight exposure makes people want to bone. Assuming the sunlight -> MCR activation assumption is true lol
Case in point, melanin synthesis and libido systems are related: There's a drug "bremelanotide" and by now probably some others, injectable melanocortin receptor agonists originally marketed for whole-body skin tanning. But actually it's marketed for libido enhancement and in the process it turned out that most MC receptor subtypes regulate mood/cognition more than skin color
TL;DR, there's evidence to suggest - in humans - that sunlight exposure makes people want to bone. Assuming the sunlight -> MCR activation assumption is true lol