It all depends on the models. When I went to the LBS to testride I automatically felt too compact on the women's bikes. I am 5'5", 160 athletic build, size 10/12. As soon as I got on the men's bike it just felt right. I think I liked the stretched out postition a little more.
A girlfriend of mine is the same height and I always thought we were pretty similar in proportion...got on her bike a Specialized Ruby and it was amazing how much different we were. I felt so squished up and short. Her frame size was smaller because her legs are shorter...who would of guessed just looking at us. (my friend and I both have two kids under 3...so that baby fat is still there too...Ugh!)
She loves her bike and I love mine... It all depends on preference and positioning. THis is why test riding is sooooo important!!!!
I ended up purchasing a '06 Trek 2100 on sale and I love it.

Good luck with the Thyroid issues... keep on that endocrinologist. I had pituitary issues in college, I understand the hormone battles!