Why can't you have an hysterectomy when you.ve got an overactive thyroid?

You can: You just need to get the thyroid under control first to be safe for the surgery. Overactive thyroid speeds up your metabolism, putting more stress on your heart and clear drugs quicker. You might have more risks during surgery if you are hyperthyroid. Thus, for non-emergent surgery, it's best to get the thyroid controlled, then go for surgery.

Anesthesia: Unless a surgery is a true emergency, your doctor won't put you at risk with anesthesia and an over active thyroid. Your doctor put your safety first by delaying until your thyroid functions are controlled.