title: The association between circulating IGF1, IGFBP3, and calcium: results from NHANES III.
abstract: BACKGROUND
  Despite mounting evidence linking both calcium and IGF1, there is a lack of studies investigating any association between circulating levels of IGF1 and serum calcium.
  
  
  METHODS
  Serum calcium, IGF1, and IGF-binding protein 3 (IGFBP3) were measured for 5368 participants in NHANES III. We calculated multivariable-adjusted geometric means of serum concentrations of IGF1, IGFBP3, and IGF1/IGFBP3 by categories of calcium (lowest 5% (<1.16 mmol/l), mid 90%, and top 5% (≥1.31 mmol/l)). We also performed stratified analyses by sex, age, ethnicity, BMI, serum levels of vitamin D, and bone mineral density (BMD).
  
  
  RESULTS
  Overall, we found that circulating calcium was positively associated with circulating levels of IGF1 and IGFBP3, but not their molar ratio (i.e., geometric mean of IGF1 by increasing calcium categories: 237.63, 246.51, and 264.22 ng/nl; Ptrend: 0.43; Pfirst vs third category: 0.01). In particular, these associations were observed in women, people aged <60, non-Hispanic whites, those with vitamin D levels above the mean, and those with low BMD. In contrast, there was an inverse association with the molar ratio for those with BMI ≥30 kg/m(2).
  
  
  CONCLUSIONS
  We found an overall positive association between circulating levels of IGF1 and IGFBP3 and serum calcium. However, stratification by potential effect-modifiers did not support all suggested hypotheses. Our findings provide more insight into the interplay between calcium and IGF1, which in the future can be investigated in larger observational studies allowing for additional stratifications based on a combination of the different effect-modifiers investigated here.
authors: Cancer Epidemiology GroupDivision of Cancer Studies, King's College London, London, UKDivision of Chronic Disease EpidemiologyEpidemiology, Biostatistics and Prevention Institute (EBPI), University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland.
authors: Mieke
authors: M
authors: Van Hemelrijck
authors: Cancer Epidemiology GroupDivision of Cancer Studies, King's College London, London, UKDivision of Chronic Disease EpidemiologyEpidemiology, Biostatistics and Prevention Institute (EBPI), University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland.
authors: Thurkaa
authors: T
authors: Shanmugalingam
authors: Cancer Epidemiology GroupDivision of Cancer Studies, King's College London, London, UKDivision of Chronic Disease EpidemiologyEpidemiology, Biostatistics and Prevention Institute (EBPI), University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland.
authors: Cecilia
authors: C
authors: Bosco
authors: Cancer Epidemiology GroupDivision of Cancer Studies, King's College London, London, UKDivision of Chronic Disease EpidemiologyEpidemiology, Biostatistics and Prevention Institute (EBPI), University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland.
authors: Wahyu
authors: W
authors: Wulaningsih
authors: Cancer Epidemiology GroupDivision of Cancer Studies, King's College London, London, UKDivision of Chronic Disease EpidemiologyEpidemiology, Biostatistics and Prevention Institute (EBPI), University of Zurich, Hirschengraben 84, 8001 Zurich, Switzerland sabine.rohrmann@ifspm.uzh.ch.
authors: Sabine
authors: S
authors: Rohrmann
keywords: IGF-1; IGFBP3; calcium; cross-sectional