Dramatic Elevation inParathyroid Hormone after Denosumab Administration in a Woman with Scleroderma

Denosumab (Prolia), an injectable human monoclonal antibody with affinity for nuclear factor-kappa ligand (RANKL), is approved for the treatment of osteoporosis in postmenopausal women and men at high risk for fracture, or patients who have failed or are intolerant of ther treatments. There have been case reports of denosumab leading to elevated parathyroid hormone (PTH) among patients with severe renal impairment, defined as creatinine clearances under 30 mL/min or on dialysis, which is the level at which the manufacturer suggests monitoring for hypocalcemia. We report a case of a marked increase in PTH in a woman with suspected malabsorption due to scleroderma, without severe renal impairment, whose intractable diarrhea limited her treatment options.