Endocrine Abstracts

Background: Primary hyperparathyroidism (PHPT) reduces bone mineral density (BMD), leading to secondary osteoporosis. While parathyroidectomy has been reported to increase BMD, the efficacy of medical therapy for PHPT-induced osteoporosis after parathyroidectomy remains uncertain. Herein, we report two PHPT cases with osteoporosis, where romosozumab, an anti-sclerostin monoclonal antibody, increased BMDs after parathyroidectomy.

Case 1: A 67-year-old woman was admitted to our department with mild hypercalcemia (10.2 mg/dl) and elevated PTH levels. She was diagnosed with osteoporosis at the age of 55 and had taken 0.75 μg eldecalcitol and 60 mg raloxifene for six months before admission. Serum calcium (reference, 8.5-9.9) and intact PTH (reference, 15-65) were 9.4 mg/dl and 110 pg/ml, respectively. Echography and ^99mTc-sestamibi (MIBI) scintigraphy revealed a 9 mm-sized parathyroid gland behind the left lobe of the thyroid. Dual-energy X-ray absorptiometry (DXA) indicated reduced BMDs with T-scores of -4.0 in the lumbar spine and -5.4 in the 33% radius. She was diagnosed with PHPT and underwent parathyroidectomy. Raloxifene was replaced with 210 mg/month of subcutaneous romosozumab 5 years after the surgery. The 12-month romosozumab therapy increased T-scores from -5.6 to -2.1 in the lumber spine and from -5.6 to -5.4 in the 33% radius.

Case 2: A 64-year-old woman with a history of urolithiasis was admitted with mild hypercalcemia (11.0 mg/dl) and elevated PTH levels. She had taken 20 mg of bazedoxifene and 0.25 μg of alfacalcidol since her diagnosis of osteoporosis at the age of 60. Serum calcium and intact PTH levels after cessation of alfacalcidol were 10.3 mg/dl and 161 pg/ml, respectively. Echography and ^99mTc-MIBI scintigraphy revealed a 20 mm-sized parathyroid gland below the right lower pole of the thyroid. DXA scans indicated reduced BMDs with T-scores of -4.1 in the lumbar spine and -4.9 in the 33% radius. She was diagnosed with PHPT and underwent parathyroidectomy, followed by a 12-month romosozumab therapy. The romosozumab treatment increased T-scores to -2.8 in the lumbar spine and -4.9 in the 33% radius.

Discussion: We present two cases of PHPT with osteoporosis, which demonstrated improved BMDs by romosozumab therapy after parathyroidectomy, especially in the lumbar spine. The absence of prior bisphosphonate treatment may enhance the effect of romosozumab on BMDs. Our cases suggest romosozumab as a potential postoperative therapy for PHPT-induced osteoporosis.