Hypoparathyroidism

A 58-year-old man is found on laboratory testing to have a serum calcium level of 6.0 mg per deciliter (normal range, 8.5 to 10.5), an albumin level of 3.9 g per deciliter, and a phosphorus level of 6.0 mg per deciliter (normal range, 2.5 to 4.5). His medical history is notable only for long-standing hearing difficulties. He reports no history of neck surgery and is asymptomatic. His ionized calcium level is 0.75 mmol per liter (normal range, 1.10 to 1.32). How should his case be further evaluated and treated?