My sister had half of her thyroid removed because of hyperthyroidism. what should she expect now since the surgery?

Thyroidectomy: Partial thyroidectomy may produce no physiologic changes. In some cases hypothyroidism can occur or parathyroid dysfunction causing low calcium.

Varies: She can expect to have normal thyroid function but some will be under active and some will still be overactive. Eventually, about 80% of people with graves disease as a cause of hyperthyroidism will become under active. So monitoring the thyroid level will be necessary for the rest of her life.