Final answer:
In cases of hypothyroidism, the missing thyroid hormone is replaced with medication. The replacement level must be carefully monitored and adjusted if needed.
Step-by-step explanation:
In cases of hypothyroidism due to Hashimoto's thyroiditis or removal of the thyroid gland to treat hyperthyroidism, the missing thyroid hormone is replaced with medication. The level of replacement thyroid hormone must be carefully monitored and adjusted if needed because thyroid hormones are responsible for vital body functions. Failing to treat even a mild thyroid disorder may lead to other problems like osteoporosis or infertility.