title: Acute response to oral calcium loading in pregnant and lactating women with a low calcium intake: a pilot study.
abstract: This pilot study in women from The Gambia with low habitual calcium intakes showed differences in calciotropic hormones between pregnant, lactating and non-pregnant, non-lactating women similar to those in Western women. The response to oral calcium loading indicates a high degree of calcium conservation independent of reproductive status.
  
  
  BACKGROUND
  In pregnancy and early lactation, parathyroid hormone (PTH) concentrations may be suppressed. Uncertainty exists about how calcium metabolism is regulated, particularly when calcium intake is low.
  
  
  METHODS
  We investigated fasting markers of calcium metabolism and the acute calcemic and calciuric responses after an oral calcium load in 30 pregnant, lactating or non-pregnant, non-lactating (NPNL) Gambian women with low habitual calcium intakes. Women received 1 g elemental calcium (CaCO3) at 0 min. Blood was collected at -30 and 180 min. Urine was collected from -60 to 0, 0-120 and 120-240 min. Samples were analysed (blood: ionized calcium (iCa); plasma (p): total calcium (tCa), phosphate (P), creatinine (Cr), PTH, 1,25-dihydroxyvitamin D (1,25(OH)2D), osteocalcin (OC), β C-terminal cross-linked telopeptide of type 1 collagen (βCTX), cyclic adenosine monophosphate (cAMP); urine (u): Ca, P, Cr, cAMP).
  
  
  RESULTS
  Pre-loading, groups did not differ significantly in iCa, pP, uCa/Cr and uP/Cr. pOC concentrations were significantly lower and NcAMP and p1,25(OH)2D higher in pregnant women; pPTH and pβCTX in lactating women were higher than in NPNL women. Post-loading, iCa, ptCa and uCa/Cr concentrations increased; pPTH, NcAMP, βCTX and uP/Cr decreased in all groups, but the magnitude of change did not differ significantly between groups.
  
  
  CONCLUSIONS
  Differences between pregnant, lactating and NPNL Gambian women in pPTH, NcAMP and p1,25(OH)2D and bone markers were similar to Western women. However, the response to calcium loading indicates that there may be no differences in renal and intestinal calcium economy associated with reproductive status, potentially due to a high degree of calcium conservation associated with low intakes.
authors: MRC Human Nutrition Research, Elsie Widdowson Laboratory, Fulbourn Road, Cambridge, CB1 9NL, UK. inez.schoenmakers@mrc-hnr.cam.ac.uk
authors: I
authors: I
authors: Schoenmakers
authors: L M A
authors: LM
authors: Jarjou
authors: G R
authors: GR
authors: Goldberg
authors: K
authors: K
authors: Tsoi
authors: D
authors: D
authors: Harnpanich
authors: A
authors: A
authors: Prentice
mesh_terms: D000284:Administration, Oral; D000328:Adult; D015415:Biomarkers / Q000097:blood; D001800:Blood Specimen Collection / Q000379:methods; D002118:Calcium / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D002136:Calcium, Dietary / Q000008:administration & dosage; D000242:Cyclic AMP / Q000097:blood; D005260:Female; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007774:Lactation / Q000097:blood* / Q000502:physiology; D010281:Parathyroid Hormone / Q000097:blood; D010710:Phosphates / Q000097:blood; D010865:Pilot Projects; D011247:Pregnancy / Q000097:blood* / Q000502:physiology
chemical_list: D015415:Biomarkers; D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D010710:Phosphates; D000242:Cyclic AMP; D002118:Calcium