I was sitting with a group of old girlfriends; old being the operative word. We meet at each other's home, with our husbands, four times a year. Weather permitting, the men play golf while the women stay behind, wolfing down chips, nuts, cheese and crackers and kvetching about how impossible it is to lose weight.
I'm sure you can think of someone whose cycles are thrown off every time they travel, have a test or are sleep-deprived. This reaction creates a chain of events that can suppress or even stop a whole range of responses, including digestion (feel bloated much?), menstruation and, you guessed it, libido.