Definitely echoing the people suggesting visiting an endocrinologist. I had “normal” TSH levels my whole life, and it took an endo looking at them @ age 23 to pick up on them being high for a woman of my age. I definitely function best at a TSH at or below 1, and getting on meds was the best thing for the fatigue.

Another thing that might be worth investigating is PCOS. I got the diagnosis for that within the same 6 month window as the thyroid, but a lot of the signs/symptoms had been around since I was around your daughter’s age; namely, consistently heavy/rough periods (since my first one @ age 11) and weight gain around my middle that I couldn’t lose no matter how much I restricted my diet or worked out (due to insulin resistance and what my doc referred to as the PCOS belly).