title: Long-term hypovitaminosis D and secondary hyperparathyroidism outcomes of the Roux-en-Y gastric bypass: a systematic review.
abstract: Pre-operative Vitamin D deficiency is markedly prevalent in prospective bariatric surgery patients. While bariatric surgery leads to significant weight loss, it can exacerbate or prolong Vitamin D deficiency. We systematically reviewed the literature to assess whether secondary hyperparathyroidism is maintained in the medium to long term in patients following the Roux-en-Y gastric bypass.
  
  
  
  A comprehensive literature search was conducted through Medline, Embase, Scopus, Web of Science, Dare, Cochrane library and HTA database. The search terms used were bariatric surgery, gastric bypass and hyperparathyroidism.
  
  
  
  Fourteen studies were included (n = 2688 subjects). Parathyroid hormone levels rose gradually from a mean pre-operative level of 5.69 ± 1.2 pmol/L to 6.36 ± 0.77 pmol/L, 7.59 ± 0.73 pmol/L and 8.29 ± 1.41 pmol/L at 2 years, between 2 and 5 years, and beyond 5 years, respectively. Vitamin D levels slowly fell to a mean of 20.50 ± 4.37 ng/mL and 20.76 ± 3.80 ng/mL between follow-up intervals 2-5 years and beyond 5, respectively.
  
  
  
  It appears that hyperparathyroidism persists at 5-year follow-up after gastric bypass, despite most patients being supplemented with calcium and Vitamin D.
authors.affiliation: Department of Surgery, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: N J
authors.identifier: 0000-0002-9273-1008
authors.initials: NJ
authors.lastname: Switzer
authors.affiliation: Department of Surgery, University of Calgary, Calgary, Alberta, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Marcil
authors.affiliation: Department of Surgery, University of Calgary, Calgary, Alberta, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Prasad
authors.affiliation: Department of Surgery, University of Calgary, Calgary, Alberta, Canada.
authors.forename: E
authors.initials: E
authors.lastname: Debru
authors.affiliation: Department of Surgery, University of Calgary, Calgary, Alberta, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Church
authors.affiliation: Department of Surgery, University of Calgary, Calgary, Alberta, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Mitchell
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, University of Calgary, Calgary, Alberta, Canada.
authors.forename: E O
authors.initials: EO
authors.lastname: Billington
authors.affiliation: Department of Surgery, University of Calgary, Calgary, Alberta, Canada.
authors.forename: R S
authors.initials: RS
authors.lastname: Gill
mesh_terms: D015390:Gastric Bypass / Q000009:adverse effects*; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000097:blood* / Q000453:epidemiology; D065228:Non-Randomized Controlled Trials as Topic; D016032:Randomized Controlled Trials as Topic; D013997:Time Factors; D014808:Vitamin D Deficiency / Q000097:blood* / Q000453:epidemiology
keywords: Gastric bypass; hyperparathyroidism; hypovitaminosis D; long-term outcomes