It's not so weird to me, I don't know much about melatonin but testosterone (probably the most popular steroid) is also just a natural hormone
I think testosterone should be legalized. There are hundreds of black market websites that sell it to US customers and its usage is actually very common. Better to take the cryptocurrency, scams, counterfeits off the market.
Thyroid hormone is prescription only, and for good reason. Hormone overdose can be dangerous.