A 55-year-old woman with celiac disease presents with diffuse bone pain and difficulty walking. Lab shows: serum calcium 7.8 mg/dL, phosphate 2.2 mg/dL, alkaline phosphatase 380 U/L, PTH 120 pg/mL (elevated), and 25-hydroxyvitamin D 10 ng/mL. The elevated PTH in this patient is best explained by:

• A Primary hyperparathyroidism due to parathyroid adenoma
• B PTH secretion driven by osteoblast stimulation in Paget's disease
• C Tertiary hyperparathyroidism from prolonged CKD
• D Secondary hyperparathyroidism due to vitamin D deficiency from malabsorption ✓

Explanation

Celiac disease causes malabsorption of vitamin B and calcium. Vitamin B deficiency leads to reduced intestinal calcium absorption, hypocalcemia, and compensatory secondary hyperparathyroidism. The low calcium, low vitamin B, and elevated PTH are classic for secondary hyperparathyroidism. Primary hyperparathyroidism would show elevated or high-normal calcium. CKD is not present here.

Reference: Harrison's Principles of Internal Medicine, 20th ed.

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Written and medically reviewed by the StethoPrep medical team.