title: Bone mass is recovered from lactation to postweaning in adolescent mothers with low calcium intakes.
abstract: BACKGROUND
  Adolescent mothers may be at increased risk of irreversible bone loss during pregnancy and lactation, particularly when calcium intake is low.
  
  
  OBJECTIVE
  Longitudinal changes in bone mass from lactation to postweaning were evaluated in 10 adolescent mothers aged 15-18 y who habitually consumed <500 mg Ca/d.
  
  
  METHODS
  Total-body bone mineral content (TBBMC), total-body bone mineral density (TBBMD), and lumbar spine bone mineral density (LSBMD) were measured at lactation (6-24 wk postpartum) and after weaning (12-30 mo postpartum). Serum hormones (intact parathyroid hormone, estradiol, and prolactin), serum calcium, and markers of bone turnover [urinary N-telopeptide cross-linking region of type I collagen (NTx) and plasma activity of bone alkaline phosphatase] were measured at lactation.
  
  
  RESULTS
  TBBMC, total calcium content, TBBMD, and LSBMD increased from lactation to postweaning (P < 0.01). TBBMD and LSBMD were, respectively, 3.6% and 9.7% lower than predicted at lactation and 0.3% and 4.8% lower than predicted in the postweaning period. The increase in age-matched TBBMD adequacy was correlated with the time after resumption of menses (r = 0.86, P < 0.01). Calcium accretion from lactation to postweaning correlated negatively with estradiol (r = -0.86) and prolactin (r = -0.69) and positively with intact parathyroid hormone (r = 0.72) and NTx (r = 0.84) measured at lactation (P < 0.05).
  
  
  CONCLUSIONS
  It appears that adolescent mothers with habitually low calcium intakes recover from lactation-associated bone loss after weaning. The rate of bone accretion, however, may not be sufficient to attain peak bone mass at maturity. Hormones regulating bone turnover during lactation may influence bone recovery in adolescent mothers.
authors.affiliation: Laboratório de Bioquímica Nutricional e de Alimentos, Instituto de Química, Universidade Federal do Rio de Janeiro, Brazil.
authors.forename: Flávia F
authors.initials: FF
authors.lastname: Bezerra
authors.forename: Laura Mc
authors.initials: LM
authors.lastname: Mendonça
authors.forename: Erika C
authors.initials: EC
authors.lastname: Lobato
authors.forename: Kimberly O
authors.initials: KO
authors.lastname: O'Brien
authors.forename: Carmen M
authors.initials: CM
authors.lastname: Donangelo
mesh_terms: D000293:Adolescent; D015519:Bone Density; D001938:Brazil; D002118:Calcium / Q000097:blood / Q000172:deficiency / Q000378:metabolism*; D005260:Female; D006801:Humans; D007774:Lactation / Q000378:metabolism*; D011247:Pregnancy; D014886:Weaning
chemical_list: D002118:Calcium