Thyroid hormonal therapy means giving or prescribing thyroid hormonal tablets, specifically, levothyroxine.
Thyroid hormonal therapy can be done for two purposes: for replacement or for suppression.
Replacement therapy is done when there is insufficient amount of thyroid hormones in the body or patient is in the state of hypothyroidism. The hypothyroidism can be surgically-induced (removal of almost total to total thyroid tissues or thyroidectomy); radiation-induced (administration of radiation, either external radiation or radioactive iodine); or non-surgically, non-radiation-induced or disease-induced (such as congenital absence of thyroid gland and chronic thyroiditis).
In replacement therapy, thyroid hormones (levothyroxine) are given to to point that the FT4 and TSH values (these are tests for thyroid function) are within the normal range. The dosage can be 25 mcg/day, 50 mcg/day, 75 mcg/day, and 100 mcg/day depending on the degree of hypothyroidism.
Suppressive therapy is done to suppress the thyroid stimulating hormone (TSH). These are usually being done in patients with colloid adenomatous goiter and thyroid cancers (particularly the papillary and follicular types).
See diagrams below showing the normal thyroid hormone system and the feedback mechanisms.
The TSH can be suppressed with administration of exogenous thyroid hormones like levothyroxine. With suppression of the TSH, colloid adenomatous goiters and thyroid cancers may be controlled in the forms of complete response (disappearance), partial response (incomplete response but stable), and prevention of recurrence.
In suppressive therapy, thyroid hormones (levothyroxine) are given to to point that the TSH values are below the normal values. The dosage can be 100 mcg/day, 200 mcg/day, and 300 mcg/day depending on what degree of suppression is needed.