For many years (pre hrt) I've always 'synched' up with whichever female I've been living with, to the point that I can tell right before they get their period by my face breaking out in pimples. Generally they've found it hilarious, like a kind of payback, but searching online for years of other examples of this occurring has always been fruitless. It's worse now on HRT, but how can this be? , I understand that cisfemales living together tend to eventually get in step with each other, but I'm at a loss to explain how a pre everything guy can be affected. Just throwing it out there as I've always wondered about it. 

Somewhere, off in the distance, a cricket chirped