Someone in the World Wide Webosphere came up with this possible solution for Cathia.
Some of the things that can affect the skin, nails, and hair
are described here.
Another one from a thyroid disease chat center
Hair thinning is definately a symptom of thyroid disorders but the nail thing is not something I have personally heard of or experienced with mine.
The first thing that I thought of was psoriasis but I am sure the doctors would have checked for that. Also fungal infections etc.
As both hair and nails are composed of keratin as a shot in the dark there may be a connection there? Some kind of deficiency?
I agree with Whit, hair thinning is defiately thyroid. Brittle nails is also, her body may be just more extreme than most others. I guess the obvious question here is has her thyroid been tested?
Anyone found any others?