Differences in single gland and multigland disease are seen in low biochemical profile primary hyperparathyroidism James Y. Lim, MD, a Max C. Herman, BS, a Lev Bubis, MD, a Irene Epelboym, MD, a John D. Allendorf, MD, b John A. Chabot, MD, a James A. Lee, MD, a and Jennifer H. Kuo, MD, a New York and Mineola, NY Background. Primary hyperparathyroidism is characterized by increased levels of serum calcium and parathyroid hormone. Recently, 2 additional mild biochemical profiles have emerged, normocalcemic and normohormonal primary hyperparathyroidism. We reviewed our surgical experience of mild biochemical profile patients and compared them with classic primary hyperparathyroidism patients. Methods. This is a single institution, retrospective cohort review of all patients who underwent parathyroidectomy for primary hyperparathyroidism from 2006–2012. Preoperative and intraoperative variables were analyzed. Univariable analysis was performed with analysis of variance and the v 2 test. A logistic regression was performed to identify significantly independent predictor variables for multigland disease. Results. A total of 573 patients underwent parathyroidectomy for primary hyperparathyroidism (classic, n = 405; normohormonal, n = 96; normocalcemic, n = 72). Normocalcemic primary hyperparathy- roidism was associated with multigland disease in 43 (45%, P < .001) patients as compared with the normohormonal (7, 10%) and classic (36, 9%) groups. On logistic regression, significant predictors for multigland disease were the normocalcemic subtype and positive family history. Twelve month biochemical normalization rates after operative treatment were >98% in all 3 groups. Conclusion. Our series shows that normocalcemic primary hyperparathyroidism is associated with a high incidence of multigland disease. Normohormonal disease is similar to classic disease patients with >90% presenting with single adenomas. Excellent rates of biochemical normalization can be obtained by operative treatment in all 3 groups. (Surgery 2016;j:j-j.) From the Division of GI/Endocrine Surgery, a Columbia University, New York, NY; and the Division of Surgical Oncology, b Winthrop Hospital, Mineola, NY PRIMARY HYPERPARATHYROIDISM is one of the most com- mon endocrine disorders with an estimated preva- lence of up to 0.9% in the United States. 1 A recent large population study found that >90% of chronic hypercalcemia is attributable to primary hyperparathyroidism. 2 The presentation of the dis- ease has also changed greatly over the years with the majority of patients now presenting with asymptomatic disease and subtle increases in routine laboratory examinations. 3 In its classic form, primary hyperparathyroidism is characterized by high serum calcium and high parathyroid hormone levels. The classic form has been associated typically with a single adenoma. Multiple studies have shown that multigland dis- ease is associated with lesser levels of serum calcium or milder disease. 3-5 More recently, 2 addi- tional subtypes with mild biochemical profiles have been described: normocalcemic and normohor- monal primary hyperparathyroidism. Normocalcemic primary hyperparathyroidism was described as early as 1969 and has been addressed only recently in the guidelines for diagnosis and management of asymptomatic pri- mary hyperparathyroidism. 6,7 Normohormonal primary hyperparathyroidism was first described in case reports in 1991 but is still not addressed Presented at the American Association of Endocrine Surgeons 2016 Annual Meeting, April 10–12, Baltimore, MD. Accepted for publication August 16, 2016. Reprint requests: Jennifer H. Kuo, MD, Division of GI/Endo- crine Surgery, Columbia University, New York, NY 10032. E-mail: Jhk2029@cumc.columbia.edu. 0039-6060/$ - see front matter Ó 2016 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.surg.2016.08.054 SURGERY 1 ARTICLE IN PRESS