It's not always hormonal. It's sometimes just a symptom of changing to the extent that what worked (or what you thought worked, or what you were simply tolerating) stops working. And suddenly. The scales fall from your eyes; you can no longer un-see what you see, or un-feel what you feel.
It is a midlife crisis, but only insofar as you realise that life is limited, and you don't want to waste it on anything that isn't meaningful or doesn't bring joy and fulfilment to your life. It is actually much more to do with death than it is to do with hormones - and our mortality can be a great motivator because it throws up a mirror to every place we've been compromising, even when didn't realise that was what we were doing.
Therapy can really help with this, and in this particular case I'd recommend a Jungian therapist/analyst, because this is where they really come into their own.
If you can stomach the highly symbolic metaphorical language, then "Descent to the Goddess" is a great book to read (Sylvia Brinton-Perera). Either that or a tome of a book that you can dip into and out of: "Women Who Run with the Wolves" by Clarissa Pinkola-Estes.
What I found when I read these was that I wasn't alone; it wasn't a mistake, what I was going through; it wasn't wrong, and in fact was a sign of something ultimately going right. I just wasn't going to put up with shit any longer. Not mine, not anyone else's. It has been the most amazing and challenging and interesting journey ever since.
All the best!