Methimazole discontinuation in Graves

Long-term methimazole continuation beyond the standard 12 to 18-month regimen addresses persistent autoimmune activation in high-risk Graves disease, where relapse rates exceed 70%. Thyrotropin-receptor antibody trajectories—classified as smooth, fluctuating, or smoldering—dictate immunologic burnout. Extending therapy to 60 months or longer reduces relapse to under 20% by maintaining low-dose enzymatic blockade of thyroid peroxidase. Crucially, major thionamide adverse events, including agranulocytosis, cluster within the first 90 days of initiation, making long-term maintenance doses of 2.5 to 7.5 mg daily a safe alternative to radioiodine ablation or surgery, particularly in patients with orbitopathy.