Calcimimetic therapy modified the radiological, surgical, and histopathological features of a parathyroid adenoma.

Calcimimetics are increasingly used to control hypercalcemia before parathyroidectomy. Although treatment-induced degenerative changes have been reported in parathyroid adenomas, their effects on preoperative imaging and surgical planning remain unclear. A 70-year-old woman with primary hyperparathyroidism was administered preoperative evocalcet (2 mg/day). After ∼2 months, serum calcium levels decreased to the hypocalcemic range, prompting drug discontinuation before surgery referral. Upon presentation, corrected serum calcium normalized to 9.1 mg/dL (SI: 2.28 mmol/L; reference range, 8.8-10.1 mg/dL [SI: 2.20-2.53 mmol/L]), whereas intact parathyroid hormone remained mildly elevated at 65.7 pg/mL (SI: 7.0 pmol/L; reference range, 10-65 pg/mL [SI: 1.1-6.9 pmol/L]). Ultrasonography revealed a right superior parathyroid lesion, with markedly decreased Doppler flow. Four-dimensional computed tomography revealed weak enhancement throughout the contrast-enhanced phase. Parathyroidectomy revealed marked fibrosis and dense adhesions around the recurrent laryngeal nerve, making dissection technically demanding, although the nerve was preserved. Histopathological examination confirmed parathyroid adenoma with extensive fibrosis, cystic degeneration, necrosis, and macrophage infiltration. Therefore, calcimimetic therapy may modify the radiological and histopathological characteristics of parathyroid adenomas and intraoperative findings relevant to surgical planning. Recognition of these treatment-induced changes may improve the interpretation of preoperative images, help surgeons anticipate dense adhesions, and facilitate meticulous surgical dissection.