A nurse is reviewing the medical record of a client who has been on levothyroxine for several months. Which of the following findings indicates a therapeutic response to the medication?

A. Increase in weight: Weight gain is often a symptom of hypothyroidism, not a therapeutic response to levothyroxine. Levothyroxine is intended to normalize thyroid function, which typically leads to weight stabilization or loss, not an increase in weight. B. Decrease in level of thyroxine (T4): Levothyroxine is used to replace thyroid hormone in clients with hypothyroidism. A decrease in T4 levels would indicate insufficient thyroid hormone levels. T4 levels should be normalized or within the reference range with proper treatment. C. Decrease in level of thyroid stimulating hormone (TSH): A decrease in TSH levels is a key indicator of a therapeutic response to levothyroxine. Levothyroxine works to normalize thyroid function, and a decreased TSH level reflects improved thyroid function and the body's ability to regulate hormone levels effectively. D. Increase in hours of sleep per night: While thyroid hormone levels can affect sleep, an increase in sleep hours is not a direct indicator of the therapeutic effect of levothyroxine. In fact, excessive sleepiness could indicate inadequate thyroid hormone replacement.