Final answer:
To assess the effectiveness of propylthiouracil in treating Graves disease, a nurse should look for decreased thyroid hormone levels which indicate a reduction in the symptoms of hyperthyroidism.
Step-by-step explanation:
A nurse assessing a client taking propylthiouracil for the treatment of Graves disease should look for symptoms that indicate a reduction in hyperthyroidism. Effective treatment would typically result in a decrease in the overactive thyroid symptoms, which includes decreased thyroid hormone levels. Therefore, among the options provided, decreased thyroid hormone levels would be a primary indicator of effective treatment with propylthiouracil. Other associated symptoms like a reduction in heart rate (bradycardia) and potential weight gain may follow as part of the general decrease in metabolic rate. Increased TSH levels would be a response to hypothyroidism, which is not directly a sign of effective treatment but rather a marker that the body needs more thyroid hormones.