A client is diagnosed with parathyroid dysfunction. Which serum calcium concentration would support the diagnosis?

• A. 7.8 mg/dL
• B. 8.9 mg/dL
• C. 9.7 mg/dL
• D. 10.2 mg/dL

Answer: (A)

Parathyroid hormone raises serum calcium, so when parathyroid function is impaired and PTH output drops, calcium in the blood falls (hypocalcemia). The value 7.8 mg/dL is below the normal range (roughly 8.5–10.5 mg/dL) and thus supports a parathyroid dysfunction scenario. The other values are normal or high, which would not reflect decreased PTH. If the issue were hyperparathyroidism, you’d expect elevated calcium, not low.