Technically as biology states, all humans have girls and boy stuff in them.
The girls have testosterone and estrogen. On their period, the levels of estrogen rise while the testosterone lowers down for 28 days. Then, the testosterone levels rises and the estrogen lowers so their period can stop.
I still don't know how the estrogen works on makls, but we have it too in us. Scientists have a theory that says that gays are "made" when a male has a higher level of estrogen than testosterone, which, honestly, makes sense to me.