Serum Bioavailable Vitamin D Concentrations and Bone Mineral Density in Women After Obesity Surgery.
Low bone mass after obesity surgery may arise as a consequence of chronic malabsorption of calcium and vitamin D. However, we have not found any role of serum 25-hydroxyvitamin D or of polymorphisms in the vitamin D receptor gene in previous studies.



To investigate the circulating bioavailable 25-hydroxyvitamin D in women after bariatric procedures and its association with bone mass.



The study consisted of 91 women on follow-up for 7 ± 2 years after bariatric surgery. We measured bone mineral density (BMD), serum parathormone (PTH), 25-hydroxyvitamin D, and vitamin D binding protein (VDBP). All patients were genotyped for two variants in the coding region of VDBP (rs4588 and rs7041). Bioavailable 25-hydroxyvitamin D was calculated in double homozygotes.



We found a negative correlation between bioavailable 25-hydroxyvitamin D and PTH (r = -0.373, P = 0.018), but not with BMD at lumbar spine (r = -0.065, P = 0.682) or hip (r = -0.029, P = 0.857). When adjusting by age, similar results were found for PTH (r = -0.441, P = 0.005), BMD at lumbar spine (r = -0.026, P = 0.874) and hip (r = -0.096, P = 0.561). After multivariate linear regression, forcing bioavailable 25-hydroxyvitamin D into the model resulted in a weak significant association with BMD at the lumbar spine (β = - 0.247, P = 0.025).



Serum bioavailable 25-hydroxyvitamin D concentrations are not associated with bone mass loss after bariatric surgery in women. The negative association with serum PTH levels suggests that vitamin D supplementation partly improves secondary hyperparathyroidism, yet other mechanisms may contribute to low bone mass after bariatric surgery.
Department of Endocrinology and Nutrition, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain. joseignacio.botella@salud.madrid.org.|Centro de Investigación Biomédica en Red-Fisiopatología de la Obesidad y Nutrición (CIBERobn) & Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), 28034, Madrid, Spain. joseignacio.botella@salud.madrid.org.
Jose I
JI
Botella-Carretero
Department of Endocrinology and Nutrition, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.
Christian
C
Lafuente
Department of Endocrinology and Nutrition, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.|Centro de Investigación Biomédica en Red-Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) & Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), 28034, Madrid, Spain.
Rafael
R
Montes-Nieto
Department of Endocrinology and Nutrition, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.|Centro de Investigación Biomédica en Red-Fisiopatología de la Obesidad y Nutrición (CIBERobn) & Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), 28034, Madrid, Spain.|Department of Endocrinology and Nutrition, Hospital Infanta Sofía, Madrid, Spain.
Jose
J
Balsa
Department of Endocrinology and Nutrition, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.
Belen
B
Vega-Piñero
Department of General and Digestive Surgery, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.
Francisca
F
Garcia-Moreno
Department of General and Digestive Surgery, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.
Roberto
R
Peromingo
Department of General and Digestive Surgery, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.
Julio
J
Galindo
Centro de Investigación Biomédica en Red-Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) & Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), 28034, Madrid, Spain.|Department of Molecular Genetics, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.
Jose L
JL
San-Millan
Department of Endocrinology and Nutrition, Hospital Universitario Ramón y Cajal, 28034, Madrid, Spain.|Centro de Investigación Biomédica en Red-Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM) & Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), 28034, Madrid, Spain.
Hector
H
Escobar-Morreale
D000328:Adult; D015904:Biliopancreatic Diversion / Q000534:rehabilitation; D015519:Bone Density / Q000235:genetics; D001851:Bone Diseases, Metabolic / Q000097:blood / Q000235:genetics; D005260:Female; D005500:Follow-Up Studies; D015390:Gastric Bypass / Q000534:rehabilitation; D020022:Genetic Predisposition to Disease; D006801:Humans; D008159:Lumbar Vertebrae; D008875:Middle Aged; D009767:Obesity, Morbid / Q000097:blood* / Q000235:genetics / Q000601:surgery*; D020641:Polymorphism, Single Nucleotide; D011183:Postoperative Complications / Q000097:blood; D014807:Vitamin D / Q000097:blood* / Q000235:genetics / Q000493:pharmacokinetics; D014809:Vitamin D-Binding Protein / Q000097:blood* / Q000235:genetics
D014809:Vitamin D-Binding Protein; D014807:Vitamin D
Bioavailable vitamin D; Bone mineral density; Obesity surgery; Secondary hyperparathyroidism