I had my Mirena IUD inserted in 2005, age 41, and was extremely happy with it at first. I'd begun to have heavy, painful periods for the first time in my life -- they immediately lightened up and the cramps went away.
I have a LOT of hair, so it took me more than 6 months to notice that it was falling out. The first time I noticed, I thought my hairdresser had thinned my hair out too much. Then I noticed fuzz growing out of the crown of my head which I'd never seen before. My hairdresser said, "Use more product." I went to a more expensive salon and consulted the owner, who said, "You're over 40. It's the menopause."
A year later, still losing hair, I got bloodwork done. My hormone profile was normal (no menopause). My thyroid was normal. I blamed the hair loss on stress.
I have now lost HALF of my hair, and finally decided to Google "Mirena hair loss". It was a nasty shock. My IUD will be removed in 10 days, and I will be changing to a different gynecologist.
I've read that as many as 1 in 20 women (5 percent) experience severe hair loss with Mirena; a poster on another website says she found this information on the manufacturer's own website, but it was soon taken down and replaced with anodyne language about "changes in hair growth".