Regarding hyperthyroidism, which of the following statements is correct?

b. Lid retraction is a sign of sympathetic overactivity and can be seen in normal individuals who ingest large amounts of thyroxine with normal thyroid function. It can be used as a fairly reliable measure of the degree of treatment with thyroidblocking medication. Hyperthyroidism is assessed clinically and confirmed biochemically with high levels of thyroid hormones (T4 and T3) and low levels of thyroid-stimulating hormone (TSH) due to negative feedback. The normal thyroid produces T4 and T3 as driven by TSH from the pituitary, which in turn is driven by hypothalamic thyroid-releasing hormone (TRH). T4 is produced in abundance relative to T3, however, T3 is 4 times more metabolically active than T4 and is converted from T4 in peripheral tissues. Symptomatic control of hyperthyroidism is achieved acutely with beta-blockade such as propranolol until thyroid-blocking agents such as propylthiouracil or carbimazole have taken effect. This usually occurs over a period of weeks and therapy must be monitored in this period with regular tests of thyroid activity until a stable dosage regime has been established.

Beta-blockade is not usually required as long-term therapy if control of overactivity can be managed medically or surgically with subtotal or total thyroidectomy (if refractory to medical treatment).