The impact of mammalian reproduction on cancellous bone architecture (original) (raw)

Pregnancy and lactation, a challenge for the skeleton

Endocrine Connections, 2020

In this review we discuss skeletal adaptations to the demanding situation of pregnancy and lactation. Calcium demands are increased during pregnancy and lactation, and this is effectuated by a complex series of hormonal changes. The changes in bone structure at the tissue and whole bone level observed during pregnancy and lactation appear to largely recover over time. The magnitude of the changes observed during lactation may relate to the volume and duration of breastfeeding and return to regular menses. Studies examining long-term consequences of pregnancy and lactation suggest that there are small, site-specific benefits to bone density and that bone geometry may also be affected. Pregnancy- and lactation-induced osteoporosis (PLO) is a rare disease for which the pathophysiological mechanism is as yet incompletely known; here, we discuss and speculate on the possible roles of genetics, oxytocin, sympathetic tone and bone marrow fat. Finally, we discuss fracture healing during pre...

Pregnancy and Lactation Confer Reversible Bone Loss in Humans

Osteoporosis International, 2001

The influence of pregnancy on bone mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry (DXA) in 73 women (mean age 29 years, range 20-44 years) postpartum. Fifty-five age-matched women served as controls. The influence of lactation was evaluated in 65 of the delivered women who were followed with repeated measurements, a mean of 4.5 + 0.1 and 11.5 + 0.1 months after the delivery. The influence of multiple pregnancies was evaluated in 39 premenopausal women (mean age 38 years, range 31-54 years) with a minimum of four pregnancies (range 4-7). Fifty-eight age-matched healthy premenopausal women with a maximum of two pregnancies (range 0-2) served as controls. Data are presented as mean + SEM. BMD data are adjusted for differences in total fat mass and total lean mass. Lumbar spine BMD was 7.6 + 0.1% and total body BMD 3.9 + 0.1% lower in women postpartum compared with controls (both p<0.001). BMD did not decrease significantly in non-breastfeeding mothers. Mothers breastfeeding for 1-6 months decreased femoral neck BMD by 2.0 + 1.0% during the first 5 months postpartum (p<0.001). No further BMD loss was seen between 5 and 12 months postpartum. Femoral neck BMD 12 months after delivery was 1.3 + 0.8% lower than after delivery in mothers breastfeeding for 1-6 months (p = 0.05). Mothers breastfeeding for more than 6 months decreased Ward's triangle BMD by 8.5 + 1.0% and lumbar spine BMD by 4.1 + 0.8% during the first 5 months postpartum (both p<0.05). No further BMD loss was seen between 5 and 12 months postpartum. Femoral neck BMD 12 months after delivery was 4.0 + 1.1% lower and Ward's triangle BMD 5.3 + 1.9% lower than after delivery in mothers breastfeeding for more than 6 months (both p<0.05). BMD loss was higher during the first 5 months following delivery in the lactating women compared with the nonlactating women (p< 0.05 comparing lumbar spine BMD loss in lactating mothers versus non-lactating mothers). However, in women with a minimum of four pregnancies the BMD was no lower than in age-matched women with fewer pregnancies. Total duration of lactation was not correlated with the present BMD. In summary, pregnancy seem to confer a low BMD with additional BMD loss during 5 months of lactation. Even if complete restoration in BMD was not reached within 5 months of weaning, women with four pregnancies or more had a BMD no lower than women with two pregnancies or fewer. We conclude that neither an extended lactation period nor multiple pregnancies could be used as a risk factor when predicting women at risk for future osteoporosis.

Changes in Bone Mineral Density During Pregnancy and Postpartum: Prospective Data on Five Women

Osteoporosis International, 1999

Areal bone mineral density (BMD, g/cm 2 ) of five healthy women (aged 26-30 years) was measured at the lumbar spine, right femoral neck and dominant distal radius with dual-energy X-ray absorptiometry before pregnancy, immediately after delivery, 1 month after the resumption of menses and 1 year thereafter. Because of the small number of subjects, only individual changes in BMD that were greater than 2H2 times the short-term in vivo precision were considered as significant changes. To obtain a further perspective, the reproduction-related BMD changes were compared with twice the standard deviation (SD) of the BMD changes in healthy premenopausal women (about ± 5%), and with the SD of the BMD in a cross-sectional sample of young healthy women. The duration of postpartum amenorrhea (PPA) and of lactation in our subjects ranged from about 2 months to 1 year and from 5 months to almost 2 years, respectively. No clear association between PPA and lactation could be seen. The magnitudes of reproductionrelated BMD changes in general seemed not to differ substantially from about ± 5% variability in BMD changes in healthy nonpregnant and nonlactating women. There was, however, some tendency toward systematic bone loss at the lumbar spine (about -3%) during pregnancy and at the femoral neck during PPA (about -5% as compared with prepregnancy data). Some individuals can yet show large, systematic bone losses comparable to 1 SD in magnitude. The site-specific reproduction-induced bone loss and consequent recovery are apparently multifactorial phenomena that may be related not only to duration and magnitude of lactation and/or duration of postpartum amenorrhea, but also to prevailing biomechanical and dietary factors, and other yet unknown individually modulated factors.

The Effects of Pregnancy and Lactation on Bone Mineral Density

Osteoporosis International, 2001

We performed a prospective study of bone mineral density (BMD) in 38 women during their first full-term pregnancy until 12 months postpartum. BMD measurements at lumbar spine [L2-L4 (LS)] and forearm [distal 33% (RD) and ultradistal (RUD) region of the radius] were made within 3 months before conception, after delivery, and at 6 and 12 months postpartum. In mid-pregnancy the DXA examination was carried out only at the forearm. Patients were grouped according to duration of lactation as group I, II or III (0-1, 1-6, 6-12 months respectively). During pregnancy there was a significant difference between baseline and delivery (p< 0.001) in the LS, RUD and RD BMD values. In group I there was no statistically significant difference in LS BMD between visits following pregnancy. The RUD BMD loss was recovered by 6 months postpartum (PP6). Group II showed continuous bone loss from delivery until PP6 at LS and RUD. In group III the LS BMD loss continued throughout the lactation period. The RUD BMD dropped (4.9%) until PP6 then increased by 3.0% as measured at 12 months postpartum (PP12). There was no significant change in RD BMD in any of three groups during lactation. At LS bone loss between delivery and PP12 correlated well with the duration of lactation (r = 70.727; p<0.001). We suggest that calcium needed for fetal skeletal growth during pregnancy was gained from maternal trabecular and cortical sites and that calcium needed for infant growth during lactation was drawn mainly from the maternal trabecular skeleton in our patients. The effect of pregnancy and lactation on the maternal bone mass was spontaneously compensated after weaning.

Lactation Delays Postpartum Bone Mineral Accretion and Temporarily Alters Its Regional Distribution in Women 1,2,3

2000

The objective of this work was to compare long-term changes in bone mineral in lactating (L) and nonlactating (NL) women for 2 y postpartum. The 40 L women (mean duration of breastfeeding 345 Ϯ 177 d) and 36 NL women were enrolled during late pregnancy. Subjects were healthy and nonsmoking with a mean age of 28.8 Ϯ 4.1 y. Bone mineral content (BMC) was measured at 0.5, 3, 6, 12, 18 and 24 mo by dual-energy X-ray absorptiometry set for total body scan with regional analysis. BMC adjusted for bone area, weight and height (adj-BMC) decreased in L women at the lumbar spine (Ϫ3.1%, P Ͻ 0.001) and pelvis (Ϫ0.9%, P ϭ 0.03) by 3 mo, and at the total body (Ϫ0.9%, P ϭ 0.05) by 6 mo. Losses were recovered following onset of menses. Adj-BMC at the lumbar spine, pelvis, thoracic spine and total body increased over baseline by 24 mo in L women. In NL women, adj-BMC increased over baseline within 3 mo and continued to increase thereafter. Net total-body gains were greater in the 27 NL women who completed the final measurement than in their 26 L counterparts (ϩ2.3% vs. ϩ0.6%, P ϭ 0.001). Net regional gains differed at the head, legs, and ribs, but not at the lumber spine, pelvis or thoracic spine. Duration of breastfeeding, parity, onset of menses and maternal age affected bone changes in L women. These results indicate that lactation delays bone mineral accretion and temporarily alters its regional distribution in postpartum women. J. Nutr. 130: 777-783, 2000.

Lactation delays postpartum bone mineral accretion and temporarily alters its regional distribution in women

The Journal of nutrition, 2000

Perinatal bone turnover in term pregnancies: The influence of intrauterine growth restriction

Bone, 2008

Intrauterine growth restriction (IUGR) has been associated with low bone mass in infancy and increased risk for osteoporosis development in adult life. We aimed to investigate the effect of IUGR on bone metabolism in mother/infant pairs, by determining circulating biochemical markers of bone turnover in IUGR and appropriate for gestational age (AGA) pregnancies. Circulating markers of bone formation [bone specific alkaline phosphatase (BALP), total alkaline phosphatase (ALP), osteocalcin (OC)] and bone resorption [cross-linked N-telopeptide of type I collagen (NTx)], as well as intact parathormone (PTH), calcium and phosphorus levels were measured in 40 mothers and their 20 IUGR and 20 AGA singleton full-term fetuses and neonates on postnatal days 1 (N1) and 4 (N4). No significant differences in BALP, ALP, OC, NTx, PTH, calcium or phosphorus levels were observed between the AGA and the IUGR groups. In both groups, maternal BALP levels were lower compared to fetal, N1 and N4 levels ( p ≤ 0.005 in all cases). In the AGA group, maternal NTx and OC levels were lower compared to fetal, N1 and N4 levels ( p b 0.001 in all cases), and fetal NTx levels were lower compared to N1 and N4 ones ( p b 0.001 and p = 0.002, respectively). In the IUGR group, maternal OC levels were lower compared to fetal, N1 and N4 ones ( p b 0.001 in each case) and fetal OC levels were elevated compared to N1 and N4 ones ( p b 0.001 and p = 0.003, respectively). N4 NTx levels were elevated compared to maternal, fetal and N1 levels ( p = 0.009, p b 0.001 and p = 0.002, respectively) and fetal NTx levels were lower compared to N1 and N4 ones ( p = 0.001 and p b 0.001, respectively). Finally, positive correlations were found between maternal NTx and BALP (r = 0.332, p = 0.037), as well as ALP (r = 0.329, p = 0.038) levels, and between maternal, fetal, N1, N4 BALP and respective ALP levels (r = 0.432, p = 0.005, r = 0.534, p = 0.001, r = 0.778, p b 0.001, r = 0.694, p b 0.001, respectively). In conclusion, maternal, fetal and neonatal bone turnover in IUGR cases may not differ from respective bone metabolism in AGA controls. In addition, fetal and neonatal bone remodeling is markedly enhanced and independent of maternal bone turnover in late pregnancy.

Bone microstructure during and after lactation

Bone, 2011

significantly below and prolactin levels decreased gradually according to breastfeeding status. IGF-levels showed a peak in the third trimester, significantly above the levels in the control group, but were below control levels in early pregnancy and following delivery. Calcitonin decreased in pregnancy and increased following delivery to the level of the controls independently of breastfeeding status (p < 0.001). PTH levels were below controls until late postpartum (p< 0.001). Compared to the controls, bone resorption as measured by urinary NTx excretion increased from early pregnancy (p< 0.001), whereas the formative markers plasma osteocalcin and bone-specific alkaline phosphatase were decreased initially, and first increased in late pregnancy to levels of the controls. The rise in bone formation correlated significantly with the peak in IGF-I. Postpartum, bone turnover changed in accordance with breastfeeding status, with increased levels in women who were breastfeeding. In conclusion: bone resorption is increased form early pregnancy until end of breastfeeding, indicating that the increased intestinal calcium absorption due to high 125(OH) 2 D levels can't by itself compensate for the increased calcium needs for fetal development. In pregnant women a delayed coupling between resorption and formation seems to exist. The increase in bone formation may be initiated by a peak in IGF-I levels. This article is part of a Special Issue entitled ECTS 2011. Disclosure of interest: None Declared.

Lactation is associated with greater maternal bone size and bone strength later in life

Osteoporosis International, 2012

The association between lactation and bone size and strength was studied in 145 women 16 to 20 years after their last parturition. Longer cumulative duration of lactation was associated with larger bone size and strength later in life. Introduction Pregnancy and lactation have no permanent negative effect on maternal bone mineral density but may positively affect bone structure in the long term. We hypothesized that long lactation promotes periosteal bone apposition and hence increasing maternal bone strength. Methods Body composition, bone area, bone mineral content, and areal bone mineral density of whole body and left proximal femur were assessed using DXA, and cross-sectional area and volumetric bone mineral density of the left tibia shaft were measured by pQCT in 145 women (mean age 48 years, range 36-60 years) 16 to 20 years after their last parturition. Hip (HSI) and tibia strength indexes (TBSI) were calculated. Medical history and lifestyle factors including breastfeeding patterns and durations were collected via a self-administered questionnaire. Weight change during each pregnancy was collected from personal maternity tracking records. Results Sixteen to 20 years after the last parturition, women who had breastfed in total more than 33 months in their life, regardless of the number of children, had greater bone strength estimates of the hip (HSI=1.92 vs. 1.61) and the tibia (TBSI= 5,507 vs. 4,705) owing to their greater bone size than mothers who had breastfed less than 12 months (p<0.05 for all). The differences in bone strength estimates were independent of body height and weight, menopause status, use of hormone replacement therapy, and present leisure time physical activity level. Conclusion Breastfeeding is beneficial to maternal bone strength in the long run.

The impact of mammalian reproduction on cancellous bone architecture (original) (raw)

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