Hi mayblin, Has anyone on here has ever started a discussion for sharing the causes of our OP? That would be really interesting. If there isn't one already, I think it would be cool if you started one.

In my case, I may not have reached my full bone density potential. That's probably true, but I did gymnastics and cheerleading--lots of impact exercise--so that can't be the whole story.

Here's the list of potential contributors that my endocrinologist and I discussed:

I was malnourished as a child and young adult.

My hormones have been a mess since puberty. There was a whole year when my menstrual cycle stopped, and perimenopause started in my early 40s.

I have anxiety, and stress out easily, so I suspect my cortisol levels are high--not yet tested.

I got Giardiasis (a parasitic disease) when living in rural Thailand. I had it for several years before it was diagnosed. That may have had lasting effects on my digestive system causing further malnutrition as an adult.

Finally there's a genetic component--my 80 year old mother has had osteoporosis since her mid-50s.