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?

A. "Drowsiness": Drowsiness is not typically associated with levothyroxine overdose. Levothyroxine is intended to increase metabolism, so drowsiness would more likely be a sign of inadequate dosing or hypothyroidism, not an overdose. B. "Constipation": Constipation is generally a symptom of hypothyroidism or insufficient thyroid hormone levels. Levothyroxine overdose would usually lead to symptoms of hyperthyroidism such as increased GI motility, not include constipation. C. "Hypoactive deep-tendon reflexes": Hypoactive deep-tendon reflexes are often seen in hypothyroidism, not hyperthyroidism. Levothyroxine overdose leads to symptoms of hyperthyroidism, such as nervousness, tachycardia, and insomnia, rather than sluggish reflexes. D. "Insomnia": Insomnia is a common symptom of levothyroxine overdose, as it can increase metabolism and stimulate the nervous system. Excess thyroid hormone increases metabolic rate, leading to symptoms such as nervousness, restlessness, increased energy levels, and difficulty sleeping due to the heightened physiological arousal.