A 63-year-old White man presents with bowing deformity of his legs, gait abnormality, and tingling and weakness in his left leg. He is diagnosed with Paget's disease of bone and asks the NP about his treatment options. Which of the following therapies is considered first line?

Choice A reason: Bisphosphonates are first-line therapy for Paget’s disease of bone. They inhibit osteoclast-mediated bone resorption, normalize bone remodeling, reduce pain, and prevent complications such as deformities and fractures. Choice B reason: Calcitonin is second-line therapy for patients intolerant of bisphosphonates. It also inhibits bone resorption but is less potent and rarely used as initial therapy. Choice C reason: Vitamin D supplementation may be used adjunctively to correct deficiency but does not treat the underlying disease process. Choice D reason: NSAIDs provide symptomatic relief of pain but do not alter bone turnover or disease progression.