Final answer:
The level of replacement thyroid hormone must be carefully monitored and adjusted if needed in cases of hypothyroidism caused by Hashimoto's thyroiditis or thyroid gland removal.
Step-by-step explanation:
When a person has hypothyroidism due to Hashimoto's thyroiditis or thyroid gland removal, they are often given medication to replace the missing thyroid hormone. The level of replacement thyroid hormone must be carefully monitored and adjusted if needed because each person's hormone requirements may differ. Monitoring ensures that the patient is receiving the right amount of thyroid hormone to maintain normal metabolism and prevent complications.