Ive gained too- was severely underweight to begin with though- but got up to overweight- without my T saying a word about it. He said A. he didn't think I was overweight (medically I was, BMI nearly 27) and B. waited for me to bring that up. I was on hormonal therapy, always hungry plus I couldn't exercise. Needless to say I felt terrible but survived. Now I'm normal weight, hoping to lose few pounds still. Don't want to start diet though- I don't trust myself with that yet. So it's going down real slow.
Bring it up- I've learned the hard way that it's exactly the things we feel deeply ashamed about that need to be discuss in a therapy.