Mf. Sowers et al., ELEVATED PARATHYROID HORMONE-RELATED PEPTIDE ASSOCIATED WITH LACTATION AND BONE-DENSITY LOSS, JAMA, the journal of the American Medical Association, 276(7), 1996, pp. 549-554
Objective.-To investigate the hypothesis that parathyroid hormone-rela
ted peptide (PTHrP) may be involved with bone loss and recovery as a m
eans of providing adequate calcium and phosphate to infants. Design.-A
n 18-month prospective cohort study. Setting.-General community settin
g with recruitment occurring at birthing education classes. Participan
ts.-Volunteer sample of 115 postpartum healthy women aged 20 to 40 yea
rs, and 0 or 1 parity prior to parturition with no intent to breast-fe
ed or intent to breast-feed at least 6 months. Main Outcome Measures.-
Parathyroid hormone-related peptide, prolactin, estradiol, 1,25-dihydr
oxyvitamin D, 25-hydroxyvitamin D, femoral bone mineral density, and b
one turnover markers were measured in 115 postpartum women at 2 weeks,
2 months, 4 months, 6 months, 12 months, and 18 months postpartum. Lu
mbar bone mineral density was measured at 2 weeks, 6 months, 12 months
, and 18 months postpartum. Results.-Elevated PTHrP values were signif
icantly associated (P<.001) with breast-feeding status, elevated prola
ctin levels, and lower serum estradiol levels, conditions occurring du
ring 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 f
or prolactin levels, breast-feeding status, return of menstruation, es
tradiol levels, PTH levels, 1,25-dihydroxyvitamin D levels, dietary ca
lcium intake, physical activity, and body size. Conclusion.-These data
clearly support the hypothesis that PTHrP is an alternative mechanism
associated with bone loss and recovery during and subsequent to lacta
tion.