A nurse is caring for a client who has a new prescription for methimazole for hyperthyroidism. Which of the following findings should the nurse report to the provider as a potentially life-threatening adverse effect?

A. Sore throat: A sore throat especially when accompanied by fever and malaise can be a sign of agranulocytosis, a potentially life-threatening side effect of methimazole. Agranulocytosis is a severe decrease in white blood cells, which can lead to infection. The nurse should report this symptom to the provider immediately, as it warrants further investigation and possible discontinuation of the medication. B. Insomnia: Insomnia is not typically a life-threatening side effect of methimazole. It may be a side effect of the hyperthyroidism itself or related to other factors, but it does not indicate a severe or immediate health risk. C. WBC count 12,000/mm3 (5,000 to 10,000/mm3): A WBC count of 12,000/mm3 is slightly elevated and may suggest an ongoing infection or inflammation. However, this value is not alarmingly high, and it does not directly indicate a life-threatening adverse effect related to methimazole. D. Weight loss of 1 kg (2.2 pounds) in 2 weeks: While methimazole aims to treat hyperthyroidism, which often causes weight loss, a small amount of continued weight loss in the initial stages of treatment might not be alarming. However, significant or continued weight loss despite treatment should be reported as it could indicate inadequate dosing or other issues.