Can the thyroid gland grow back after a partial removal?

Yes. After partial removal, the remaining thyroid will grow. If this thyroid remnant is healthy, it can easily make enough thyroid hormone to keep your blood levels normal, but on exam it may be enlarged. If the original surgery was for a "nodule", then this enlarging thyroid remnant can create concern/confusion: is it normal physiologic expansion, or another nodule? Check with your endocrinologist.