thin coat

Help! My almost 2yr old female has a smooth coat that is so thin, her skin is visible beneath. She is also so sensitive to touch on her rump, sides, and belly that she will squeal and nip sometimes when touched in these locations, usually if her fur is stroked against the growth. She is fed lamb and rice food. Could she have a thyroid problem or is this common for the breed? The vet just said it's a JRT trait...