title: Low 24-hour urine calcium levels in patients with sporadic primary hyperparathyroidism: is further evaluation warranted prior to parathyroidectomy?
abstract: BACKGROUND
  Low 24-hour urine calcium (uCa) levels in patients with primary hyperparathyroidism (pHPT) raise concern for familial hypocalciuric hypercalcemia. This study evaluated patients with a low 24-hour uCa level for potential differences that may guide the extent of preoperative evaluation needed.
  
  
  METHODS
  A retrospective review was conducted of 1,139 sporadic pHPT patients who underwent parathyroidectomy between December 1999 and May 2011.
  
  
  RESULTS
  Of the 54 (5%) patients with greater than or equal to one low 24-hour uCa (<100 mg), 28 (52%) patients had only one low level, 9 (17%) had multiple low levels, and 17 (31%) had a repeat 24-hour uCa greater than 100. In the latter group, 4 of the 9 (53%) patients were on a thiazide and had normalization after cessation. Among the groups, differences existed only in serum creatinine (P = .0011) and glomerular filtration rate (P = .0007).
  
  
  CONCLUSIONS
  This study suggests that sporadic pHPT patients with low 24-hour uCa levels may not require further evaluation with genetic testing for familial hypocalciuric hypercalcemia, especially if previous eucalcemia is documented.
authors.affiliation: Department of Surgery, Division of Surgical Oncology, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI 53226, USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: O'Connell
authors.affiliation: Department of Surgery, Division of Surgical Oncology, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI 53226, USA.
authors.forename: Tina W
authors.initials: TW
authors.lastname: Yen
authors.affiliation: Department of Medicine, Division of Clinical Endocrinology, Metabolism, and Nutrition, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI 53226, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Shaker
authors.affiliation: Department of Surgery, Division of Surgical Oncology, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI 53226, USA.
authors.forename: Stuart D
authors.initials: SD
authors.lastname: Wilson
authors.affiliation: Department of Surgery, Division of Surgical Oncology, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI 53226, USA.
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Evans
authors.affiliation: Department of Surgery, Division of Surgical Oncology, Medical College of Wisconsin, 9200 W. Wisconsin Avenue, Milwaukee, WI 53226, USA. Electronic address: tswang@mcw.edu.
authors.forename: Tracy S
authors.initials: TS
authors.lastname: Wang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002118:Calcium / Q000652:urine*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D049950:Hyperparathyroidism, Primary / Q000601:surgery* / Q000652:urine*; D008297:Male; D008875:Middle Aged; D016105:Parathyroidectomy; D011300:Preoperative Care; D012189:Retrospective Studies; D013997:Time Factors
chemical_list: D002118:Calcium
keywords: 24-Hour urine calcium; Familial hypocalciuric hypercalcemia; Primary hyperparathyroidism