There are currently three options in the treatment of hyperthyroidism. One is medical therapy. Second is surgical therapy. Third is radioactive iodine therapy. Most the time, medical therapy is usually started as an initial treatment in preparation for surgical therapy and radioactive iodine therapy. It is usually not considered as a definitive treatment for hyperthyroidism because of the reported high incidence of recurrences.
Lately, I saw two patients with hyperthyroidism who were treated with propylthiouracil, one for 2 years and the other for 3 years. One was 23 years old and the other 33 years old at the time of diagnosis. The size of their thyroid glands was not clinically obvious (enlarged) at the time of diagnosis but their FT4 levels were high and TSH levels low. On follow-up after 2 years, there was no evidence of recurrence.
These anecdotes tend to point to the possibility of using medical therapy as a definitive and not just as an initial treatment for hyperthyroidism. Hyperthyroidism, from my experience, can be classified into transient and permanent ones. The permanent ones are due to autoimmune diseases. The transient ones are due to nonspecific causes which may spontaneously regress. It is in the transient ones that medical therapy will suffice.