I am writing about my daughter, 15 years old. Always underweight and active, over the last 6 months she has become lethargic and gained weight, without a change in diet. She is bloated in face and mid section. Constipation and some hair loss . Also, attention problems, unable to focus, which has not been problem in the past. I m thinking thyroid disfunction? I ve heard of middle aged women having this, how common is it for teenagers?