What condition is effectively treated with methimazole?

Methimazole is effective in treating hyperthyroidism, a condition characterized by an overactive thyroid gland producing excessive amounts of thyroid hormones. By inhibiting the synthesis of these hormones, methimazole helps to reduce thyroid hormone levels and alleviate symptoms associated with hyperthyroidism, such as weight loss, nervousness, and an increased heart rate.

In contrast, other conditions listed—such as hypothyroidism, diabetes, and heart failure—do not respond to methimazole. Hypothyroidism involves insufficient production of thyroid hormones and typically requires replacement therapy, such as levothyroxine. Diabetes involves different mechanisms of insulin regulation and glucose metabolism, and heart failure management focuses on improving cardiac output and fluid balance rather than thyroid hormone activity.