Elevated parathyroid hormone-related peptide associated with lactation and bone density loss.
OBJECTIVE
To investigate the hypothesis that parathyroid hormone-related peptide (PRHrP) may be involved with bone loss and recovery as a means of providing adequate calcium and phosphate to infants.


METHODS
An 18-month prospective cohort study.


METHODS
General community setting with recruitment occurring at birthing education classes.


METHODS
Volunteer sample of 115 postpartum healthy women aged 20 to 40 years, and 0 or 1 parity prior to parturition with no intent to breast-feed or intent to breast-feed at least 6 months.


METHODS
Parathyroid hormone-related peptide, prolactin, estradiol, 1,25-dihydroxyvitamin D, 24-hydroxyvitamin D, femoral bone mineral density, and bone turnover markers were measured in 115 postpartum women at 2 weeks, 2 months, 4 months, 6 months, 12 months, and 18 months postpartum. Lumbar bone mineral density was measured at 2 weeks, 6 months, 12 months, and 18 months postpartum.


RESULTS
Elevated PTHrP values were significantly associated (P<.001) with breast-feeding status, elevated prolactin levels, and lower serum estradiol levels, conditions occurring during lactation. Furthermore, elevated PTHrP levels were negatively and significantly associated (P<.01) over time with bone mineral density change at both the spine and the femoral neck, even after accounting for prolactin levels, breast-feeding status, return of menstruation, estradiol levels, PTH levels, 1,25-dihydroxyvitamin D levels, dietary calcium intake, physical activity, and body size.


CONCLUSIONS
These data clearly support the hypothesis that PTHrP is an alternative mechanism associated with bone loss and recovery during and subsequent to lactation.
Sowers
M F
MF
Department of Epidemiology, University of Michigan, Ann Arbor, USA.
Hollis
B W
BW
Shapiro
B
B
Randolph
J
J
Janney
C A
CA
Zhang
D
D
Schork
A
A
Crutchfield
M
M
Stanczyk
F
F
Russell-Aulet
M
M
D015502:Absorptiometry, Photon; D015519:Bone Density / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D001942:Breast Feeding; D015331:Cohort Studies; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D015592:Immunoradiometric Assay; D007774:Lactation / Q000097:blood / Q000502:physiology*; D010281:Parathyroid Hormone / Q000097:blood / Q000502:physiology*; D044162:Parathyroid Hormone-Related Protein; D049590:Postpartum Period / Q000502:physiology; D011388:Prolactin / Q000097:blood; D011446:Prospective Studies; D011506:Proteins / Q000032:analysis / Q000502:physiology*; D012044:Regression Analysis; D012680:Sensitivity and Specificity
C470121:PTHLH protein, human; D010281:Parathyroid Hormone; D044162:Parathyroid Hormone-Related Protein; D011506:Proteins; D004958:Estradiol; D011388:Prolactin