High physiological prolactin induced by pituitary transplantation decreases BMD and BMC in the femoral metaphysis, but not in the diaphysis of adult female rats

High physiological prolactin (PRL) stimulated intestinal calcium absorption and renal calcium uptake in mammals. Previous histomorphometric study revealed a significant increase in bone turnover in the trabecular part of the PRL-exposed long (cortical) bone; however, whole-bone densitometric analysis was unable to demonstrate such effect. We therefore studied differential changes in bone mineral density (BMD) and contents (BMC) of the femoral diaphysis and metaphysis in adult female rats exposed to high PRL induced by anterior pituitary (AP) transplantation. The estrogen-dependent effects of PRL on the femur were also investigated. We found that chronic exposure to PRL had no effect on BMD or BMC of the femoral diaphysis, which represented the cortical part of the long bone. It is interesting that 7 weeks after an AP transplantation, BMD and BMC of the femoral metaphysis were significantly decreased by 8% and 14%, respectively. Ovariectomy (Ovx) for 2, 5, and 7 weeks also decreased BMD and BMC in the femoral metaphysis, but not in the diaphysis. However, the AP transplantation plus Ovx (AP+Ovx) produced no additive effects. Nevertheless, 2.5 microg/kg 17beta-estradiol (E2) supplementation abolished the osteopenic effects of both Ovx and AP+Ovx on the femur. As for the L5-6 vertebrae, BMD and BMC were not affected by PRL exposure, but were significantly decreased by Ovx and AP+Ovx, and such decreases were completely prevented by E2 supplementation. It could be concluded that high physiological PRL induced a significant osteopenia in the trabecular part, i.e., the metaphysis, of the femora of adult female rats in an estrogen-dependent manner. Since PRL had no detectable effect on the vertebrae, the effects of PRL on bone appeared to be site-specific.     

Increased bone mineral density in the femora of GDF8 knockout mice

GDF8 (myostatin), a member of the transforming growth factor (TGF)-beta superfamily of secreted growth and differentiation factors, is a negative regulator of skeletal muscle growth. GDF8 knockout mice have approximately twice the skeletal muscle mass of normal mice. The effects of increased muscle mass on bone modeling were investigated by examining bone mineral content (BMC) and bone mineral density (BMD) in the femora of female GDF8 knockout mice. Dual-energy X-ray absorptiometry (DEXA) densitometry was used to measure whole-femur BMC and BMD, and pQCT densitometry was used to calculate BMC and BMD from cross-sections taken at two different locations: the midshaft and the distal metaphysis. The DEXA results show that the knockout mice have significantly greater femoral BMD than normal mice. The peripheral quantitative computed tomography (pQCT) data indicate that the GDF8 knockout mice have approximately 10% greater cortical BMC (P =.01) at the midshaft and over 20% greater cortical BMC at the metaphysis (P <.001). Likewise, knockouts show approximately 10% greater cortical thickness (P <.001) and significantly greater cortical BMD (P <.001) at both locations. These results suggest that inhibitors of GDF8 function may be useful pharmacological agents for increasing both muscle mass and BMD.     

Changing patterns of daily rhythmicity across reproductive states in diurnal female Nile grass rats (Arvicanthis niloticus)

A suite of changes in circadian rhythms have been described in nocturnal rodents as females go through pregnancy and lactation, but there is no information on such patterns in diurnal species. As the challenges faced by these two groups of animals are somewhat different, we characterized changes in activity and core body temperature (T_b) in female diurnal Nile grass rats (Arvicanthis niloticus) as they went through a series of reproductive states: virgin, pregnant, pregnant and lactating, lactating only, and post-weaning. The phase of neither rhythm varied, but the amplitude did. Females increased their overall levels of daily activity from early to late pregnancy, regardless of whether they were also lactating. The pattern of activity was less rhythmic during early than mid-lactation, in both non-pregnant and pregnant females, as a consequence of a decrease in daytime relative to nighttime activity. The T_b rhythm amplitude dropped from mid-pregnancy through mid-lactation, and there were rises in T_b troughs during the mid-light and mid-dark phases of the day, though pregnancy and lactation affected T_b at these times in somewhat different ways. This study demonstrates that rhythms in diurnal grass rats change during pregnancy and lactation in different ways than those of nocturnal species that have been studied to date and that the effects of pregnancy and lactation are not additive in any simple way.     

不同剂量糖皮质激素对大鼠骨密度和生物力学性能的影响

目的通过双能X射线骨密度仪(dual energy X-ray absorptiometry,DXA)、骨生物力学测试及骨组织计量学等方法研究不同剂量糖皮质激素摄入对正常3月龄大鼠骨骼的影响。方法 31只SPF级3月龄SD雌性大鼠,随机分为正常对照组、地塞米松(Dex)1、2.5、5 mg/kg组,每周尾静脉注射给药2次,共8周,对照组给予生理盐水对照。给药结束后,离体股骨和第3腰椎通过DXA进行骨矿含量(bone mineral content,BMC)、骨矿密度(bone mineral density,BMD)测定,全股骨和第5腰椎分别进行三点弯曲和压缩力学实验,并通过骨组织病理切片观察胫骨近端骨小梁的显微结构并定量分析。结果与正常组相比,所有激素组大鼠体重均明显降低,腰椎BMC、BMD及最大压缩载荷均未明显下降,全股骨BMC均有所降低,但只有Dex 1 mg组全股骨和股骨远端、近端BMD降低;Dex 1 mg组三点弯曲实验断裂载荷、最大载荷和弹性载荷都明显降低,而Dex 2.5 mg、Dex 5 mg组只有弹性载荷仍低于正常对照组。激素组骨小梁有空间密度分布不均现象,骨代谢处于低转换。结论应用糖皮质激素8周对3月龄大鼠骨骼的不利影响股骨较腰椎明显,股骨骨量丢失,力学性能下降,两者均无剂量依赖性。更高剂量Dex并没有增加骨量丢失和力学性能改变。力学性能特别是弹性载荷下降以及骨小梁密度分布不均,提示糖皮质激素更多的是引起骨质量下降。临床上应用糖皮质激素时,应使用多种方法评价其对骨骼的副作用。     

Treadmill running starting 3 months after orchidectomy restores femoral bone mass in rats

The present study was designed to provide data on the effects on femoral bone of endurance training starting only 3 months after orchidectomy in rats. A total of 70 Wistar male rats were used at 8 weeks of age. On day 0 of the experiment, 10 rats were killed by cervical dislocation to be used as first controls. Among the 60 other animals, half was surgically castrated (CX) or sham operated (SH). On day 90, 10 CX and 10 SH were killed and used as intermediary controls (ICX and ISH). Among the other 20 CX and 20 SH, 10 within each group (CXE, SHE) were selected for treadmill running (60% maximal oxygen uptake, 1?h?·?day^?1, 5?days?·?week^?1 for 12 weeks). The 20 other rats were used as sedentary controls (CXR, SHR) and killed (as runners) on day 180. On day 90 femoral bone density (BMD) and mineral content (BMC) were lower in ICX than in ISH. On day 180 total femoral BMD was lower in CXR than in CXE. Simultaneously metaphyseal femoral BMD was lower in CXR than in CXE, SHR or SHE. Furthermore, at that time, no significant difference concerning BMD and BMC was observed between SHR and CXE. This would indicate that treadmill running starting only 3 months after orchidectomy is able to restore BMD and BMC to control values, mainly by inhibiting bone resorption (as shown by decreased urinary deoxypyridinoline excretion in CXE) without decreasing osteoblastic activity (evaluated by plasma osteocalcin concentration).     

Comparison of volumetric bone mineral density in the tibial region of interest for ACL reconstruction

Adequate tibial bone mineral density (BMD) is essential to soft tissue graft fixation during anterior cruciate ligament (ACL) reconstruction. The purpose of this study was to compare volumetric bone plug density measurements at the tibial region of interest for ACL reconstruction using a standardized immersion technique and Archimedes’ principle. Cancellous bone cores were harvested from the proximal, middle, and distal metaphyseal regions of the lateral tibia and from the standard tibial tunnel location used for ACL reconstruction of 18 cadaveric specimens. Proximal tibial cores displayed 32.6% greater BMD than middle tibial cores and 31.8% greater BMD than distal tibial cores, but did not differ from the BMD of the tibial tunnel cores. Correlational analysis confirmed that the cancellous BMD in the tibial tunnel related to the cancellous BMD of the proximal and distal lateral tibial metaphysis. In conjunction with its adjacent cortical bone, the cancellous BMD of the region used for standard tibial tunnel placement provides an effective foundation for ACL graft fixation. In tibia with poor BMD, bicortical fixation that incorporates cortical bone from the distal tibial tunnel region is recommended.     

低应力环境对大鼠股骨的骨密度和几何形态学的影响

切断6周大鼠的坐骨神经,使其右后肢处于低应力环境中。测量股骨不同部位的骨密度和几何形态学参数。结果发现,低应力环境下大鼠股骨的直径、皮质骨面积和骨矿密度的增加明显受抑制。但不同部位的骨密度对低应力环境的敏感性不同,表现为早期富于松质骨的股骨干骺端骨密度增加幅度的受抑,接着是富于皮质骨的骨干部的骨密度增长幅度的降低。几何形态学结果提示,早期干骺端骨密度增长幅度的降低是由于骨吸收增强,而皮质骨的骨量和尺寸的增长受抑制是骨膜骨形成持续减少的结果。     

Periprosthetic bone mineral density changes after unicondylar knee arthroplasty

BackgroundUnicompartmental knee arthroplasty (UKA) has received renewed interest in the last decade. UKA involves minor injury to soft tissues, limited removal of bone and delicate preservation of knee anatomy and geometry. In theory, UKA provides an opportunity to restore post-surgical knee kinematics to near normal.HypothesisUKA leaves patellofemoral joint free to meet high mechanical forces with no stress-shielding and therefore might preserve bone mineral density (BMD).Patients and methodsWe studied 21 patients with osteoarthritis(OA), who had received medial compartment UKA at Kuopio University Hospital between October 1997 and September 2000. BMD was measured by dual-energy X-ray absorptiometry (DEXA), at baseline (within a week after surgery) and at intervals until 7 years.ResultsDEXA results were reproducible. The highest rate of periprosthetic bone loss occurred during the first 3 months after UKA. The average loss in BMD was 4.4% (p = 0.039) in the femoral diaphysis and it ranged from 11.2% (p < 0.001) to 11.9% (p = 0.002) in the distal femoral metaphysis; however, BMD changes in these regions, from 2 years to 7 years, were nonsignificant. At the 1-year follow-up, the BMD of the medial tibial metaphysis had increased by 8.9% (p = 0.02), whereas those in the lateral tibial metaphysial (–2.4%) and diaphysial regions (–2.0%) did not change significantly.InterpretationsUKA did not preserve periprosthetic BMD in the distal femoral metaphysis, whereas BMD changes in the tibial metaphysis were minor, consistent with a mechanical balance between the medial and lateral tibial compartments.Level of Evidence 2bProspective case control study.     

Liver L-carnitine biosynthesis in non-pregnant, pregnant and lactating rabbits

The present study reports liver carnitine biosynthesis and concentrations in non-pregnant (dry), pregnant and lactating rabbits (n = 17). To determine carnitine biosynthesis in liver tissues; we purified gamma-butyrobetaine hydroxylase, a key enzyme in carnitine biosynthesis, and measured its activity. An isocratic high-performance liquid chromatography (HPLC) method was used to determine L-carnitine levels in liver samples. When compared with dry period, during pregnancy, free and acid-soluble total carnitine concentrations did not change significantly (p>0.05). In contrast to free and acid-soluble total carnitine, short chain acylcarnitine concentration increased significantly in the second period of pregnancy, compared with non-pregnant rabbits. Highest concentrations of free, short-chain acyl- and acid-soluble total carnitine were measured at the 4th day of lactation (487 +/- 29; 392 +/- 26 and 879 +/- 38 nmol/g wet weight respectively). gamma-Butyrobetaine hydroxylase activity increased with the duration of pregnancy and in late pregnancy it increased significantly compared to previous periods. Highest activity was measured in early lactation period (361 +/- 28 pmol carnitine/min/mg protein). We concluded that, biosynthesis of carnitine in liver increases gradually in late pregnancy and early lactation in rabbit, and this may be regulated by hormonal changes during these periods.     

妊娠、分娩以及泌乳期大鼠下丘脑中食欲素及其受体表达的变化

目的 观察大鼠下丘脑中食欲素(Orexin)及其受体(OX1R、OX2R)在妊娠、分娩以及泌乳期表达的变化,以探讨Orexin与生殖功能之间的关系.方法 通过竞争性逆转录多聚酶链式反应(Competitive RT-PCR)和免疫组织化学方法测定大鼠下丘脑中Orexin前体(Prepro-OX)、Orexin-A、OX1R和OX2R在妊娠、分娩以及泌乳期的表达.结果 Orexin-A和OX1R阳性神经元主要分别存在于大鼠下丘脑外侧区(LHA)以及妊娠和泌乳期大鼠的下丘脑室旁核 (PVN)和视上核(SON).泌乳第1d的Prepro-Orexin mRNA和OX1R的表达水平明显高于妊娠后期和泌乳期.OX2R的表达在生殖各时期之间没有明显改变.结论 Orexin可能参与大鼠泌乳早期的生殖功能调节,下丘脑的PVN及SON可能是其重要的作用部位.     

Comparison of bone mineral content and bone mineral density between dominant and nondominant limbs in children 8–16 years of age

The bone mineral content (BMC), bone mineral density (BMD), and bone free lean tissue (BFLT) of dominant limbs were compared to nondominant values in girls and boys 8–16 years of age (girls, n = 124; boys, n = 110). Results showed that BMC, BMD, and BFLT of the dominant arm was significantly greater than of the nondominant arm (P < .01). The differences were found for both boys and girls and across all age groups except for 8 to 9-year-old boys for BMC. There were no differences in BMC or BMD in the legs, but the dominant leg had significantly greater BFLT than the nondominant leg (P < .01). The greater BMC and BMD values of the dominant arm are likely a result of greater mechanical loading (resulting from normal daily activities) of the dominant arm; this speculation is supported by the greater muscularity in the dominant arm. In the legs it is likely that weight bearing and not bias muscular activity is more important in determining bone mineral status. © 1993 Wiley-Liss, Inc.     

Potentially increased sensitivity of pregnant and lactating female rats to immunotoxic agents

Characteristic susceptibility to environmental and pharmaceutical exposure may occur during periods in life of marked histophysiological changes of the immune system. Perinatal development is such a period; pregnancy followed by lactation is potentially another one. Here, we explored the influence of pregnancy and lactation on the model immunotoxic compound di-n-octyltin dichloride (DOTC) in rats using clinical and histopathological parameters. Female rats were exposed to 0, 3, 10, or 30 mg DOTC/kg feed during pregnancy and up to 20 (at weaning) or 56 days after delivery. Age-matched nonmated females were exposed during the same time periods. DOTC at the level of 10 and 30 mg/kg decreased thymus weight and affected thymus morphology in the lactating rats. In addition, DOTC decreased the numbers of neutrophils in the lactating rats. These effects were no longer apparent at day 56 despite continuous exposure to DOTC. This explorative study indicates that the innate and adaptive immune system may be especially sensitive to immunotoxicants during pregnancy and lactation.     

Evidence for a major gene for bone mineral density/content in human pedigrees identified via probands with extreme bone mineral density

Bone mineral content (BMC) and/or bone mineral density (BMD, i.e. BMC scaled by bone size) are major determinants for osteoporosis, which is a serious health problem. The major determinant of variation in BMD/BMC is genetic. The few studies now available are inconsistent in the identification and/or even in the existence of major gene(s) for BMD/BMC. In 51 human pedigrees with 941 individuals (526 measured for phenotypes) identified via probands with extreme BMD values, we performed complex segregation analyses to test the existence of a genetic locus with a major effect on BMD/BMC variation. We analyzed BMD and BMC at the spine, hip and wrist jointly by employing, as the study phenotype, factor scores (FS) of the principle component that explains ∼75% of the total BMD/BMC variation at the three sites. The results indicate that a major gene exists with a codominant effect that is responsible for ∼16% of the FS variation when adjusted for significant effects of sex, body weight and age. A significant genotype-×-sex-×-age interaction was found, which may explain ∼14% of the FS variation after adjusting for body weight. Testing of various models did not provide support for shared familial environmental effects but suggested the existence of residual polygenic effects, which may explain ∼50% of the FS variation when adjusting for sex, body weight and age. This study indicates a promising aspect of studies to identify a major gene for BMD/BMC variation in our pedigrees identified via extreme probands.     

An investigation of ethnic differences in bone mineral, hip axis length, calcium metabolism and bone turnover between West African and Caucasian adults living in the United Kingdom.

The aim of the study was to investigate factors relating to calcium and bone metabolism which might explain the low incidence of osteoporotic fracture among Africans. Adult bone mineral status, hip axis length and biochemical indices were investigated in 20 Caucasians (10 male, 10 female) and 19 Gambians (12 male, 7 female) living in the UK. Bone mineral content (BMC), bone mineral density (BMD) and BMC adjusted for bone area, body weight and height (size-adjusted BMC) were measured for the whole-body, lumbar spine, femoral neck, trochanter, radius shaft and radius wrist using dual-energy X-ray absorptiometry. There were no significant differences in whole body or regional BMC; values tended to be lower in the Gambians. Gambian men had higher size-adjusted BMC at the femoral neck (Gambian-British = 21%, 95% CI = 6 to 36%, p < 0.01), associated with a smaller bone area (Gambian-British = -11%, 95% CI = -20 to -2%, p = 0.02). BMD was affected similarly. No other significant differences in BMD or size-adjusted BMC were observed. Gambians had shorter hip axis length (Gambian British, after accounting for sex, = -5%, 95% CI = -9 to -1%, p = 0.02). There were no significant differences in bone turnover (osteocalcin, bone isoenzyme of alkaline phosphatase, urinary deoxypyridinoline) or calciotropic hormone levels (parathyroid hormone, 1,25-dihydroxyvitamin D, calcitonin). Gambian men had lower 25-hydroxyvitamin D concentrations (Gambian = 26.3 SD 12.0 nmol/L, British = 55.5 SD 13.9 nmol/L, p < 0.0001), a difference not seen among the women. Gambian men and women excreted significantly less phosphate and potassium than British subjects by 30-60%; urinary calcium and sodium excretion were similar in the two groups. This study revealed few ethnic differences that could account for the disparity in osteoporotic fracture rates between Africans and Caucasians, with the possible exception of anatomical differences in the hip.     

磁场对去卵巢大鼠骨密度、骨强度和骨代谢的影响

本文研究了旋转恒定磁场对去卵巢大鼠骨密度，骨强度和骨代谢的影响。结果表明磁场处理30分钟且加钙组的骨密度，能量吸收，弹性能量吸收，最大载荷，最大桡度和弹性桡度等指标均显著高于去卵巢组，分别增加3.5%,15.4%,12.4%,7.6%,5.8%,11.9%t 5.2%。其碱性磷酸酶，血磷，血钙等指标也比去卵巢组分别高71％，108％，156％。实验还检测了暴磁1个月及停止暴磁后1到2个月，大鼠骨密度和骨矿含量的变化，结果表明磁场处理存在着窗口效应和滞后效应。     

A 12-month treatment with tenofovir does not impair bone mineral accrual in HIV-infected children

BACKGROUND: Short-term use of tenofovir (TDF) has been associated with bone mineral loss in adults and children. OBJECTIVE: To assess whether the substitution of stavudine with TDF would result in decreased bone mineral content (BMC) and bone mineral density (BMD) accrual in HIV-infected children. METHODS: The lumbar spine and whole-body BMC and BMD were measured by dual-energy x-ray absorptiometry in 16 HIV-infected children (age range: 6.4-17.9 years) on stable highly active antiretroviral therapy. Bone measurements were obtained 12 months before the switch, at baseline, and 12 months after switching to TDF. Expected changes in bone measurements were calculated from cross-sectional data obtained from 166 healthy children. RESULTS: The BMC and BMD increments observed before switching therapy did not differ from expected increments. Similarly, the changes detected during treatment with TDF did not differ significantly from those calculated in healthy controls. CONCLUSIONS: Substitution to a TDF-containing antiretroviral regimen does not seem to impair bone mineral accrual in children showing a good immunologic response to antiretroviral treatment.     

The effects of hyaluronan on bone resorption and bone mineral density in a rat model of estrogen deficiency-induced osteopenia

Hyaluronan, or hyaluronic acid (HA), is an essential component of extracellular matrices. HA of appropriate molecular weight and concentration can induce osteoblast differentiation and bone formation in vitro. The aim of our study was to evaluate the effects of HA of different molecular weights on ovariectomy (OVX)-induced bone loss in rats. Adult female Sprague Dawley rats were subjected to bilateral OVX or sham surgical procedure (sham). OVX rats were treated with: HA of molecular weight of 0.75 MDa at a dose of 1 mg/kg/day and with HA of molecular weight of 1.62 MDa at a dose of both 0.5 mg/kg/day and 1 mg/kg/day. HA was applied orally once a day during the 8-week period after ovariectomy. Body weight, urinary pyridinoline (Pyr), deoxypyridinoline (DPyr) corrected for urinary creatinine, serum nitrite/nitrate concentrations and whole body and femoral bone mineral density (BMD) were measured. HA treatment had no effect on the body weight gain in OVX rats. Excretion of urinary Pyr and Dpyr significantly increased in OVX rats compared to sham controls. The higher molecular weight HA (1.62 MDa) significantly reduced urinary Pyr and DPyr concentrations measured on day 28 after ovariectomy (p < 0.001). Serum concentrations of nitric oxide metabolites, nitrite/nitrate significantly decreased in OVX rats in comparison with sham controls (p < 0.001). HA of both 0.75 MDa and 1.62 MDa molecular weights significantly enhanced serum nitrite/nitrate concentrations in OVX rats. There was a clear reduction of whole body and femoral BMD in untreated OVX rats. The higher molecular weight HA decreased both whole body and femoral BMD loss. Our results show that orally applied HA of high molecular weight (1.62 MDa) inhibits bone resorption and provides a protective effect on bone density in ovariectomized rats.     

去卵巢大鼠骨密度变化与骨髓组织血管生成的关系

目的： 探讨去卵巢大鼠骨密度变化与骨髓组织血管生成的关系。方法：30只SD雌性大鼠随机分为去卵巢组（OVX）和假手术组（sham）,分别在4周、8周和12周处死。取左侧股骨测量骨密度(BMD)。右侧远端股骨干骺端松质骨甲醛固定,EDTA-Na2脱钙。常规脱水、石蜡包埋、切片。行苏木素－伊红染色用于观察骨髓组织病理改变,用CD34标记血管内皮细胞观察微血管密度(MVD),采取大鼠腹主动脉血进行血管内皮生长因子(VEGF)测定。结果： 大鼠去卵巢8周后BMD明显低于假手术组, 提示骨质疏松模型建立,此时,骨髓造血组织容量减少,脂肪组织容量增高,与假手术组比较均有显著差异（P<0.01）,骨髓组织MVD与假手术组比略有减少。12周后,上述改变更为明显。同时,骨小梁容量减少,骨髓组织MVD明显减少（P<0.05）,且显示MVD与BMD、造血组织容量和骨小梁容量呈正相关,与脂肪组织容量呈负相关。但血浆VEGF含量测定OVX组与sham组间无明显差异,与骨髓组织各形态指标亦无相关性。结论：去卵巢大鼠在骨量丢失和造血组织容量减少的同时伴有骨髓组织MVD减少, 为骨质疏松症采用促微血管增生治疗提供了实验依据。     

Increased bone mineral density is associated with breastfeeding history in premenopausal Spanish women

Introduction

During lactation abundant calcium is lost from the mother as a result of the amount of breast milk produced. Lactation leads to transient fragility, with some women experiencing even fragility fractures, but nearly all of these women subsequently undergo a large increase in bone mineral density (BMD), confirming that the BMD must have declined during lactation but it increases after weaning. We have retrospectively examined the relationship between the duration of breastfeeding and bone properties in Spanish premenopausal healthy women, to identify the site-specific changes in BMD.

Material and methods

Four hundred and thirty-three premenopausal healthy women, 295 with a mean of 7.82 ±6.68 months of exclusive breastfeeding and 138 control women, were studied. We examined total, trabecular and cortical volumetric BMD (mg/mm³) at the distal radius using peripheral quantitative computed tomography. Areal BMD (g/cm²) was measured using dual energy X-ray absorptiometry at the femoral neck, lumbar spine, trochanter and Ward''s triangle. Phalangeal bone ultrasound was measured by amplitude-dependent speed of sound.

Results

Areal BMD analysis at L2–L4 revealed significant intergroup differences (p < 0.05). There were significant intergroup differences in the volumetric BMD in both total and cortical bone (p < 0.05). The observed BMD of breast-feeders was higher than the BMD in non-breast-feeding women. Additionally, the lactation subgroup analysis revealed significant differences in the areal BMD at trochanter and L2–L4 (p < 0.05) and in the cortical volumetric BMD (p < 0.05).

Conclusions

This study adds to the growing evidence that breastfeeding has no deleterious effects and may confer an additional advantage for BMD in premenopausal women.