Problems with asthma following treatment of thyrotoxicosis.

We describe two cases of asthma associated with concomitant thyrotoxicosis where initial improvement followed antithyroid treatment. Relapse of asthma on thyroxine replacement was accompanied by subclinical hyperthyroidism with elevated levels of triiodothyronine. This emphasizes the need to follow up asthmatic patients closely for biochemical relapse following treatment of thyrotoxicosis.