A nurse is assessing a client who is taking levothyroxine. The nurse should recognize that which of the following findings is a manifestation of levothyroxine overdose?

Levothyroxine overdose results in iatrogenic hyperthyroidism, producing excess thyroid hormone (T3/T4) with increased basal metabolic rate, sympathetic overactivity, and heightened adrenergic sensitivity affecting cardiovascular, neurologic, and gastrointestinal systems. Rationale: A. Constipation is associated with decreased gastrointestinal motility seen in hypothyroidism. Excess levothyroxine increases intestinal transit leading to diarrhea rather than constipation. This finding reflects underactive thyroid state, not hormone overdose or thyrotoxic physiology. B. Hypoactive deep-tendon reflexes occur in hypothyroidism due to slowed neuromuscular conduction. Levothyroxine overdose produces hyperreflexia and rapid relaxation phase. Reduced reflexes contradict increased thyroid hormone effect and are not consistent with toxic thyroid hormone excess state. C. Drowsiness is a feature of hypothyroidism resulting from reduced CNS metabolic activity. Levothyroxine overdose causes CNS stimulation, anxiety, and restlessness rather than sedation. This option represents low thyroid hormone state and not pharmacologic toxicity or excess replacement effect. D. Insomnia occurs due to adrenergic stimulation and increased metabolic activity from excess levothyroxine. Thyroid hormone overdose enhances CNS excitability causing sleep disturbance, agitation, and restlessness. This is a classic manifestation of iatrogenic hyperthyroidism and reflects excessive dosing or sensitivity to therapy.