Surgically proven normocalcemic primary hyperparathyroidism: speculation of the possible role of estrogen in the etiology of this disease in premenopausal women.

We herein report a rare case of surgically proven normocalcemic primary hyperparathyroidism (NCHPT). A premenopausal 51-year-old woman was referred to our clinic because parathyroid adenoma was detected on neck ultrasonography (US). The patient's serum calcium concentration was 9.3 mg/dL and the intact parathyroid hormone (PTH) level was 128.8 pg/mL. The findings of almost all other examinations were also compatible with a diagnosis of NCHPT. Then, parathyroidectomy was performed. The serum calcium and PTH concentrations reduced significantly but remained within the normal ranges. A histological examination demonstrated parathyroid adenoma. A review of this case and the associated literature suggests that estrogen plays a significant role in the etiology of NCHPT in premenopausal women.