title: Role of vitamin D levels and vitamin D supplementation on bone mineral density in Klinefelter syndrome.
abstract: This manuscript describes the role of low vitamin D in bone metabolism of Klinefelter subjects. Low vitamin D is frequent in this condition and seems to be more important than testosterone in inducing low bone mineral density (BMD) and osteoporosis. Supplementation with vitamin D restores BMD after 2 years of treatment, whereas testosterone alone seems to be ineffective.
  
  
  BACKGROUND
  Decreased bone mineral density (BMD) in Klinefelter syndrome (KS) is frequent, and it has been traditionally related to low testosterone (T) levels. However, low BMD can be observed also in patients with normal T levels and T replacement therapy does not necessarily increase bone mass in these patients. Nothing is known about vitamin D levels and supplementation in KS. In this study, we determine vitamin D status and bone mass in KS subjects and compare the efficacy of T therapy and vitamin D supplementation on BMD.
  
  
  METHODS
  A total of 127 non-mosaic KS patients and 60 age-matched male controls were evaluated with reproductive hormones, 25-hydroxyvitamin D, PTH, and bone densitometry by dual-energy X-ray absorptiometry (DEXA). Patients with hypogonadism and/or 25-hydroxyvitamin D deficiency were treated with T-gel 2% and/or calcifediol and re-evaluated after 24 months of treatment.
  
  
  RESULTS
  25-hydroxyvitamin D levels were significantly lower in KS patients with respect to controls, and they had significantly lower lumbar and femoral BMD. The percentage of osteopenia/osteoporosis in subjects with 25-hydroxyvitamin D deficiency was higher with respect to subjects with normal 25-hydroxyvitamin D and was not related to the presence/absence of low T levels. Subjects treated with calcifediol or T + calcifediol had a significant increase in lumbar BMD after treatment. No difference was found in T-treated group.
  
  
  CONCLUSIONS
  These data highlight that low 25-hydroxyvitamin D levels seem to have a more critical role than low T levels in inducing low BMD in KS subjects. Furthermore, vitamin D supplementation seems to be more effective than T replacement therapy alone in increasing BMD.
authors.affiliation: Department of Medicine and Centre for Human Reproduction Pathology, University of Padova, Via Giustiniani 2, 35100, Padova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Ferlin
authors.forename: R
authors.initials: R
authors.lastname: Selice
authors.forename: A
authors.initials: A
authors.lastname: Di Mambro
authors.forename: M
authors.initials: M
authors.lastname: Ghezzi
authors.forename: A
authors.initials: A
authors.lastname: Di Nisio
authors.forename: N
authors.initials: N
authors.lastname: Caretta
authors.forename: C
authors.initials: C
authors.lastname: Foresta
mesh_terms: D000328:Adult; D000886:Anthropometry / Q000379:methods; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000187:drug effects* / Q000502:physiology; D002112:Calcifediol / Q000494:pharmacology / Q000627:therapeutic use*; D019587:Dietary Supplements; D005272:Femur Neck / Q000503:physiopathology; D020249:Hormone Replacement Therapy / Q000379:methods; D006801:Humans; D007713:Klinefelter Syndrome / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000097:blood / Q000188:drug therapy / Q000209:etiology* / Q000503:physiopathology; D012189:Retrospective Studies; D013739:Testosterone / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D014807:Vitamin D; D013739:Testosterone; C104450:25-hydroxyvitamin D; D002112:Calcifediol