A nurse is teaching a client who has a new prescription for levothyroxine (T4) about thyrotoxicosis. The nurse should instruct the client to monitor and report which of the following findings?

Fever is a key manifestation of thyrotoxicosis, also called thyroid storm, and a client taking levothyroxine should be instructed to monitor for and report this finding immediately. Thyrotoxicosis is a life-threatening condition resulting from excess thyroid hormone, which causes a hypermetabolic state. Fever occurs because elevated thyroid hormone increases metabolic rate and thermogenesis. Other signs of thyrotoxicosis include tachycardia, diaphoresis, hypertension, agitation, and in severe cases cardiovascular collapse. Drowsiness and weight gain are symptoms associated with hypothyroidism — the condition levothyroxine is prescribed to treat — not with excess thyroid hormone activity. Bradycardia is likewise a feature of hypothyroidism, not thyrotoxicosis; an excess of thyroid hormone produces tachycardia instead. Because levothyroxine can be accidentally overdosed or because dosing needs may change, clients must be educated to recognize signs of excessive thyroid hormone activity. Fever is the most acute warning sign that signals a potentially dangerous shift toward thyrotoxicosis, making it the correct finding to monitor and report.