Sera from patients with Graves' disease may contain a mixture of TSH-R(s) and TSH-R(b) antibodies interacting with the TSH-R; these antibodies may have different affinities and titre, which may change spontaneously or as a result of therapy. Changes in the titres of stimulating and blocking antibodies to the TSH-R can be responsible for fluctuating thyroid function where the thyroid state of the patient spontaneously changes from hypothyroidism to hyperthyroidism, or vice versa. A similar mechanism may also be responsible for transient changes of thyroid function (Fig. 17.14).
