Bone physiology during pregnancy and lactation in young macaques

The various meanings and uses of bone "remodeling" in biological anthropology: A review

OBJECTIVES

In modern bone biology, the term "remodeling" generally refers to internal bone turnover that creates secondary osteons. However, it is also widely used by skeletal biologists, including biological anthropologists as a catch-all term to refer to different skeletal changes. In this review, we investigated how "remodeling" is used across topics on skeletal biology in biological anthropology to demonstrate potential problems with such pervasive use of a generalized term.

METHODS

Using PubMed and Google Scholar, we selected and reviewed 205 articles that use the term remodeling to describe skeletal processes and have anthropological implications. Nine edited volumes were also reviewed as examples of collaborative work by different experts to demonstrate the diverse and extensive use of the term remodeling.

RESULTS

Four general meanings of bone "remodeling" were identified, namely, internal turnover, functional adaptation, fracture repair, and growth remodeling. Additionally, remodeling is also used to refer to a broad array of pathological skeletal changes.

DISCUSSION

Although we initially identified four general meanings of bone remodeling, they are not mutually exclusive and often occur in combination. The term "remodeling" has become an extensively used catch-all term to refer to different processes and outcomes of skeletal changes, which inevitably lead to misunderstanding and a loss of information. Such ambiguity and confusion are potentially problematic as the field of biological anthropology becomes increasingly multidisciplinary. Therefore, we advocate for precise, context-specific definitions and explanations of bone remodeling as it continues to be used across disciplines within and beyond biological anthropology.

Elemental composition of primary lamellar bone differs between parous and nulliparous rhesus macaque females

Extracting life history information from mineralized hard tissues of extant and extinct species is an ongoing challenge in evolutionary and conservation studies. Primary lamellar bone is a mineralized tissue with multidien periodicity that begins deposition prenatally and continues until adulthood albeit with concurrent resorption, thus maintaining a record spanning several years of an individual's life. Here, we use field-emission scanning electron microscopy and energy-dispersive X-ray analysis to measure the relative concentrations of calcium, phosphorous, oxygen, magnesium and sodium in the femora of seven rhesus macaque with known medical and life-history information. We find that the concentration of these elements distinguishes parous from nulliparous females; that in females calcium and phosphorus are lower in bone formed during reproductive events; and that significant differences in relative magnesium concentration correlate with breastfeeding in infants.

The effects of parity and litter size on bone metabolic activity in pregnant and lactating sows

During gestation and lactation, female mammals often mobilize endogenous nutrient reserves to meet the resource demands of offspring production. These mobilized stores include calcium, phosphorous and other minerals that are resorbed from maternal bone to facilitate rapid mineralization of offspring bones. The extent to which bone mineral is resorbed is governed by the total amount of mineral taken in from the diet, but also by the competing demands of offspring and the minimum level of bone density that a female must sustain to support self-maintenance. The maximum amount of bone that a female may mobilize is undoubtedly dependent a variety of maternal traits, including age and reproductive experience (i.e., parity). We evaluated changes in serum concentrations of biomarkers of metabolic activity (total deoxypyridinoline [tDPD] and osteocalcin [OC]) of maternal bone and its relationship to reproductive output and parity throughout pregnancy and lactation in Yorkshire sows. Litter size did not affect bone metabolism; however, serum concentrations of both tDPD and OC were significantly higher in sows with little or no reproductive experience when compared to sows that had produced at least 3 litters prior to the current reproductive bout. This suggests a shift in ability or physiological strategy to meet offspring mineral demands that is acquired or associated with reproductive experience.

Could use of Selective Serotonin Reuptake Inhibitors During Lactation Cause Persistent Effects on Maternal Bone?

The lactating mammary gland elegantly coordinates maternal homeostasis to provide calcium for milk. During lactation, the monoamine serotonin regulates the synthesis and release of various mammary gland-derived factors, such as parathyroid hormone-related protein (PTHrP), to stimulate bone resorption. Recent evidence suggests that bone mineral lost during prolonged lactation is not fully recovered following weaning, possibly putting women at increased risk of fracture or osteoporosis. Selective Serotonin Reuptake Inhibitor (SSRI) antidepressants have also been associated with reduced bone mineral density and increased fracture risk. Therefore, SSRI exposure while breastfeeding may exacerbate lactational bone loss, compromising long-term bone health. Through an examination of serotonin and calcium homeostasis during lactation, lactational bone turnover and post-weaning recovery of bone mineral, and the effect of peripartum depression and SSRI on the mammary gland and bone, this review will discuss the hypothesis that peripartum SSRI exposure causes persistent reductions in bone mineral density through mammary-derived PTHrP signaling with bone.

Mechanical and metabolic interactions in cortical bone development

OBJECTIVES

Anthropological studies of cortical bone often aim to reconstruct either habitual activities or health of past populations. During development, mechanical loading and metabolism simultaneously shape cortical bone structure; yet, few studies have investigated how these factors interact. Understanding their relative morphological effects is essential for assessing human behavior from skeletal samples, as previous studies have suggested that interaction effects may influence the interpretation from cortical structure of physical activity or metabolic status.

MATERIAL AND METHODS

This study assesses cross-sectional geometric and histomorphometric features in bones under different loading regimes (femur, humerus, rib) and compares these properties among individuals under different degrees of metabolic stress. The study sample consists of immature humans from a late medieval Lithuanian cemetery (Alytus, 14th-18th centuries AD). Analyses are based on the hypothesis that metabolic bone loss is distributed within the skeleton in a way that optimizes mechanical competency.

RESULTS

Results suggest mechanical compensation for metabolic bone loss in the cross-sectional properties of all three bones (especially ribs), suggesting a mechanism for conserving adequate bone strength for different loads across the skeleton. Microscopic bone loss is restricted to stronger bones under high loads, which may mitigate fracture risk in areas of the skeleton that are more resistive to loading, although alternative explanations are examined.

DISCUSSION

Distributions of metabolic bone loss and subsequent structural adjustments appear to preserve strength. Nevertheless, both mechanics and metabolism have a detectable influence on morphology, and potential implications for behavioral interpretations in bioculturally stressed samples due to this interaction are explored. Am J Phys Anthropol 160:317-333, 2016. © 2016 Wiley Periodicals, Inc.

Vitamin D -- the sun hormone. Life in environmental mismatch

While some representatives of the animal kingdom were improving their biological mechanisms and properties for adapting to ever-changing life conditions, the genus Homo was developing backward: human individuals were losing their adaptation to life areas conquered earlier. Losing step-by-step their useful traits including the body hair cover, the primitive genus Homo retained his viability only under very favorable conditions of the equatorial Africa. Protection from UV radiation danger was provided only by pigmentation of skin, hair, and eyes. However, "impoverished" individuals of this genus gained the ability to walk upright. Their hands became free from participation in movement and became fine tools for producing useful instruments, from the stone knife to the computer. The major consequence of upright movement and hand development became the powerful development of the brain. A modern human, Homo sapiens, appeared capable of conquering very diverse new habitats. The human's expansion on the Earth occurred somewhat limited by his dependence on vitamin D. His expansion into new areas with lower Sun activity was partially associated with the loss of skin pigmentation. But there is an open question, whether under these new conditions he is satisfactorily provided with vitamin D. This paper discusses the following problems: how can we ensure a sufficient intake of vitamin D, how much does an individual require for his existence and optimal life, what will be consequences of vitamin D deficiency, and what are the prospects for better provision with vitamin D?

The effect of locomotion on the mobilization of minerals from the maternal skeleton

Bone is a dynamic tissue from which minerals are deposited or withdrawn according to the body’s demand. During late pregnancy and lactation, female mammals mobilize mineral from bone to support the ossification of offspring skeleton(s). Conversely, in response to mechanical loading, minerals are deposited in bone enabling it to develop a stronger architecture. Despite their central importance to reproductive performance and skeletal integrity, the interactions between these potentially opposing forces remains poorly understood. It is possible that inter-individual differences in the loading imposed by different forms of locomotion may alter the amount of mineral mobilized during reproduction. Here, the impact of vertical versus horizontal locomotion on bone mobilization was examined during reproduction in the laboratory mouse. The vertical, or climbing, group had access to a 60-cm tower, increasing strain on their appendicular skeleton. The horizontal, or tunnel, group had access to a 100-cm tunnel, which encouraged movements within the horizontal plane. Form of locomotion did not impact the amount of bone females mobilized during reproduction or the amount of mineral females deposited in the litter, but maternal bone architecture differed between groups. The climbing group displayed more trabeculae than the tunnel group, whereas the tunnel group displayed greater cortical bone mineral density mid-shaft. Interestingly, pups born to mothers in the climbing group had a higher concentration of total body calcium at 16 days than pups of mothers in the tunnel group. As maternal total body calcium composition and the amount of calcium invested in the full litter were not different between groups, the difference in the relative calcium content of pups between groups is not suspected to reflect difference in mineral allocation. Future research should consider the impact of maternal activity on the efficiency of offspring skeletal ossification via hormones and other bioactive factors transferred in utero and in milk.

Reductions in heel bone quality across gestation are attenuated in pregnant adolescents with higher prepregnancy weight and greater increases in PTH across gestation

Few studies have examined the effect of maternal calcium intake and vitamin D status on bone health across gestation in pregnant adolescents. This study aimed to characterize maternal bone quality and determinants of bone-quality change across gestation in pregnant adolescents. Healthy pregnant adolescents (n = 156; aged 13 to 18 years) with singleton pregnancies and at 12 to 30 weeks gestation at enrollment were recruited from two urban maternity clinics in Baltimore, MD, and Rochester, NY, for this prospective longitudinal study. Maternal serum was collected at midgestation and at delivery for assessment of bone biomarkers and calcitropic hormones. Maternal bone quality (assessed by heel ultrasound) and sonographic fetal biometry were measured up to three times across pregnancy. Racially diverse teens (64.7% African American, 35.3% white) were followed from 21.0 (interquartile range [IQR] 17.3, 27.0) weeks of gestation until delivery at 40.0 (IQR 39.0, 40.7) weeks. Significant decreases in calcaneal speed of sound (SOS), broadband ultrasound attenuation (BUA), and quantitative ultrasound index (QUI) (-9.2 ± 16.1 m/s, -3.2 (-8.0, 2.1) dB/MHz and -5.3 ± 8.8, respectively) were evident across pregnancy. Multivariate analysis controlling for baseline measures and measurement intervals was used to identify independent predictors of normalized (per week) calcaneal bone loss. Weekly decreases in bone quality were not significantly associated with maternal calcium intake or 25(OH)D concentration. Greater weekly reductions in calcaneal bone quality were evident in teens with lower prepregnancy weight (BUA, p = 0.006 and QUI, p = 0.012) and among those with lower weekly increase in PTH (SOS, p = 0.046). Overall, significant decreases in calcaneal bone quality occurred across pregnancy in adolescents, but the magnitude of this loss was attenuated in those with greater prepregnancy weight and weekly increases in PTH. Further studies are needed to understand the role of elevated PTH and greater prepregnancy weight in preserving adolescent bone during pregnancy.

Daughter dearest: Sex-biased calcium in mother's milk among rhesus macaques

Mother's milk provides building blocks necessary for infant development and growth postnatally. Minerals in milk are particularly important for infant skeletal development and may reflect maternal characteristics that are associated with the capacity to synthesize milk and sex-specific developmental priorities of the infant. Using a large sample of mother-infant dyads assigned to the outdoor breeding colony at the California National Primate Research Center (N=104), we investigated the relationship of milk calcium (Ca) and phosphorus (P) concentrations and the ratio of Ca/P to maternal and infant characteristics and to other milk variables. Ca and P are largely associated with casein micelles, and as expected, both Ca and P were positively correlated with protein concentrations in milk. Neither Ca nor P concentrations were associated with maternal parity. Mothers rearing daughters tended to produce higher mean Ca concentration in milk, and consequently a higher Ca/P ratio, than did mothers rearing sons, even though protein concentration was not elevated. These results suggest that the Ca/P ratio in rhesus milk may have been under separate selective pressure from protein content to facilitate the accelerated rate of skeletal calcification that has been observed in female Macaca mulatta infants.

Calcium availability influences litter size and sex ratio in white-footed mice (Peromyscus leucopus)

The production of offspring typically requires investment of resources derived from both the environment and maternal somatic reserves. As such, the availability of either of these types of resources has the potential to limit the degree to which resources are allocated to reproduction. Theory and empirical studies have argued that mothers modify reproductive performance relative to exogenous resource availability and maternal condition by adjusting size, number or sex of offspring produced. These relationships have classically been defined relative to availability of energy sources; however, in vertebrates, calcium also plays a critical role in offspring production, as a considerable amount of calcium is required to support the development of offspring skeleton(s). We tested whether the availability of calcium influences reproductive output by providing female white-footed mice with a low-calcium or standard diet from reproductive maturity to senescence. We then compared maternal skeletal condition and reproductive output, based on offspring mass, offspring number and litter sex ratio, between dietary treatments. Mothers on the low-calcium diet exhibited diminished skeletal condition at senescence and produced smaller and strongly female-biased litters. We show that skeletal condition and calcium intake can influence sex ratio and reproductive output following general theoretical models of resource partitioning during reproduction.

Dietary calcium and phosphate restriction in guinea-pigs during pregnancy: fetal mineralization induces maternal hypocalcaemia despite increased 1α,25-dihydroxycholecalciferol concentrations

Guinea-pig fetuses at term are mineralized to a degree comparable with human fetuses, which makes the guinea-pig an attractive animal model to study maternal–fetal interactions with regard to Ca and phosphate (P) homeostasis. We studied non-pregnant and pregnant (day 57) vitamin D-replete guinea-pigs, fed either a normal guinea-pig chow with 9·6 g Ca/kg and 4·9 g P/kg or a study diet with 2 g Ca/kg and 1 g P/kg (low-Ca–P diet) for 7–8 weeks. Both pregnancy and the low-Ca–P diet decreased plasma concentrations of 25-hydroxycholecalciferol (25(OH)D3), but increased total and free 1α,25-dihydroxycholecalciferol (1,25(OH)2D3), strongly suggesting an additive stimulation of 1α-hydroxylase activity. Maternal and fetal 25(OH)D3and 1,25(OH)2D3levels were highly correlated (r0·82 and 0·92 respectively, P<0·001). Dual-energy absorption X-ray absorptiometry (DXA) showed that both pregnancy and the low-Ca–P diet decreased bone mineral density (BMD) of the maternal femur, particularly at the distal metaphysis. Despite higher 1,25(OH)2D3concentrations and lower BMD, pregnant animals on the low-Ca–P diet were hypocalcaemic; blood Ca2+levels were inversely correlated with the number of fetuses in this group (r-0·93, P<0·001). Fetal growth as well as mineralization (assessed by whole-body and femoral DXA, bone histomorphometry and plasma–bone osteocalcin measurements) were unaltered in the low-Ca–P group. In conclusion, fetal mineralization proceeds normally but induces maternal hypocalcaemia in guinea-pigs with dietary restriction of Ca and P.

Bone mass changes in vivo during the entire reproductive cycle in rats feeding different dietary calcium and calcium/phosphorus ratio content

The purpose of this study was to quantify in vivo the impact of different dietary Ca contents on the maternal total skeleton and skeletal sub-areas in adult rats during pregnancy and lactation, using DXA. Twenty-four female Wistar rats (approximately 5 months old) were mated and divided into three groups (n = 8) and fed one of the following diets, varying only in Ca content (LCD: 0.14%, NCD: 0.6% or HCD: 1.2%). Pups were adjusted to 8-9 per dam. Maternal ionic calcium and in vivo bone mineral density (BMD) were measured at the beginning, after delivery and after weaning. Regardless of the diet, ionized calcium decreased from onset to weaning ( P < 0.05). At weaning, bone mass decreased 7.3% in NCD, 15% in LCD and 10.5% in HCD from initial values. Total skeleton, whole and proximal tibia and spine BMDs only decreased at delivery in the LCD group ( P < 0.05) but, irrespective of the diet, at weaning, they were lower compared to delivery and initial values ( P < 0.05). LCD group presented the lowest BMD in the proximal tibia and spine regions ( P < 0.05). At birth, pups did not present differences, however, at weaning, LCD pups reached the lowest body weight ( P < 0.05), NCD presented the highest body Ca content ( P < 0.05) and there were no differences between LCD and HCD. This in vivo study showed that regardless of the dietary calcium content, the maternal skeleton is slightly affected by pregnancy but severely affected by lactation. However, the degree of such response appears to depend not only on dietary Ca content but also on dietary Ca/P molar ratio.

Effect of Duration of Alcohol Consumption on Calcium and Bone Metabolism During Pregnancy in the Rat

BACKGROUND

Little is known about the consequences of drinking during pregnancy for the long-term health of the mother. Alcohol (ethanol) has been shown to disrupt calcium (Ca) homeostasis and is known to have deleterious effects on bone. During pregnancy, bone turnover is increased to maintain Ca homeostasis; therefore, pregnancy may be a time of life when maternal bone is particularly susceptible to the effects of ethanol. This study investigated the effect of duration of ethanol consumption on Ca homeostasis and bone during pregnancy in the rat.

METHODS

Rats were fed ethanol (36% ethanol-derived calories) in liquid diets for 3 (21 days gestation only) or 6 (3 weeks before and throughout 21 days gestation) weeks. Maternal blood was analyzed for Ca (total and ionized Ca [iCa]), the Ca-regulating hormones (parathyroid hormone [PTH], 1,25(OH)2D, calcitonin), and osteocalcin (a marker for bone formation). Bone was analyzed for ash (mineral) content.

RESULTS

Dams consuming ethanol (E dams) had decreased blood Ca levels (total and iCa) at both 3 and 6 weeks, but iCa was lower in E dams after 6 compared with 3 weeks. Importantly, ethanol seemed to interfere with the normal compensatory response to these decreased Ca levels. In contrast to pair-fed controls, serum PTH levels actually were decreased, 1,25(OH)2D levels failed to increase, and calcitonin levels were increased in ethanol-consuming dams, regardless of duration. Moreover, ethanol decreased bone formation, as indicated by serum osteocalcin levels, after both 3 and 6 weeks consumption, and after 6 weeks, the ash content of bone also was decreased. In addition, a relationship was found between the blood alcohol concentration (BAC) and some measures of Ca and bone metabolism. Serum 1,25(OH)2D and osteocalcin levels varied inversely, whereas serum calcitonin varied directly with BAC, suggesting that time of sampling after drinking may be an important variable for interpreting ethanol's effects on Ca and bone metabolism. In all rats, serum osteocalcin levels varied directly with PTH and 1,25(OH)2D levels.

CONCLUSIONS

Ethanol consumption during pregnancy impaired Ca homeostasis in the dam, regardless of duration of consumption, and resulted in decreased bone formation and ash content of bone. Significant relationships among the Ca-regulating hormones, BAC, and osteocalcin support the hypothesis that ethanol's effects on the Ca-regulating hormones may mediate some of its effects on bone.

Effect of parity on bone mineral density in female rhesus macaques from Cayo Santiago

This cross-sectional study investigates the relationship between parity, bone mineral density, and spontaneous osteopenia/osteoporosis in a large skeletal population of female rhesus macaques (Macaca mulatta) from the free-ranging colony of Cayo Santiago, Puerto Rico. The sample consists of 119 mature female monkeys aged 4.0-22.2 years at time of death. The data consist of measurements of bone mineral content (BMC) and bone mineral density (BMD), obtained from dual-energy X-ray absorptiometry (DEXA) of the last lumbar vertebra. After controlling for age, there is a significant increase in BMD of the spine with increasing parity (P = 0.0006), up to a parity of 7 offspring. Thus, high parity initially has a positive effect on BMD in female rhesus monkeys, but this positive effect disappears with parities that are greater than 7 offspring. After controlling for parity, however, age has a negative (P = 0.015) effect on BMD, beginning several years after the attainment of peak BMD (age 9.5 years). Thus, it appears that parity initially mitigates the effects of aging, but the positive effect of parity on BMD is eventually overwhelmed by the aging process. Mean BMC and BMD values are higher in parous females compared to nulliparous females in the same age range. Similarly, females with low parity have significantly lower mean BMD values than do age-matched high-parity controls, and the frequency of osteopenia and osteoporosis is greater in low-parity females. Forty-three percent (43%) of the osteopenic/osteoporotic females in the sample are members of the low-parity group, even though it composes only 13% (16/119) of the entire sample. This study demonstrates that the free-ranging female rhesus monkeys from Cayo Santiago are a good nonhuman primate model for the study of bone mineral density, parity, osteopenia, and osteoporosis.

Release of lead from bone in pregnancy and lactation

Concentrations and isotope ratios of lead in blood, urine, 24-h duplicate diets, and hand wipes were measured for 12 women from the second trimester of pregnancy until at least 8 months after delivery. Six bottle fed and six breast fed their infants. One bottle feeder fell pregnant for a second time, as did a breast feeder, and each was followed semicontinuously for totals of 44 and 54 months, respectively. Bone resorption rather than dietary absorption controls changes in blood lead, but in pregnancy the resorption of trabecular and cortical bone are decoupled. In early pregnancy, only trabecular bone (presumably of low lead content) is resorbed, causing blood leads to fall more than expected from hemodilution alone. In late pregnancy, the sites of resorption move to cortical bone of higher lead content and blood leads rise. In bottle feeders, the cortical bone contribution ceases immediately after delivery, but any tendency for blood leads to fall may be compensated by the effect of hemoconcentration produced by the postpartum loss of plasma volume. In lactation, the whole skeleton undergoes resorption and the blood leads of nursing mothers continue to rise, reaching a maximum 6-8 months after delivery. Blood leads fall from pregnancy to pregnancy, implying that the greatest risk of lead toxicity lies with first pregnancies.

Neonatal bone mass: influence of parental birthweight, maternal smoking, body composition, and activity during pregnancy

Evidence is accumulating that intrauterine growth and development may influence an individual's risk of osteoporosis in later adult life. To examine maternal and paternal influences on intrauterine skeletal growth, we used dual-energy X-ray absorptiometry to measure the neonatal bone mineral content (BMC) and bone mineral density (BMD) of 145 infants born at term. Independently of the infant's duration of gestation at birth, the birthweights of both parents and the height of the father were positively correlated with neonatal whole body BMC. Women who smoked during pregnancy had infants with a lower whole body BMC and BMD; overall, there was a 7.1-g (11%) average difference between whole body BMC of infants whose mothers did and did not smoke during pregnancy (p = 0.005). Women with thinner triceps skinfold thicknesses (reflecting lower fat stores) and those who reported a faster walking pace and more frequent vigorous activity in late pregnancy also tended to have infants with a lower BMC and BMD (p values for BMC; 0.02, 0.03, and 0.05, respectively). Maternal thinness and faster walking pace but not maternal smoking or parental birthweight also were associated with lower bone mineral apparent density (BMAD). The influences on skeletal growth and mineralization were independent of placental weight, a marker of the placental capacity to deliver nutrients to the fetus. These observations point to a combination of genetic and intrauterine environmental influences on prenatal skeletal development and suggest that environmental modulation, even at this early stage of life, may reduce the risk of osteoporosis in adulthood.

Evidence for common controls over inheritance of bone quantity and body size from segregation analysis in a pedigreed colony of nonhuman primates (Macaca nemestrina)

The genetic determinants of bone mineral quantity and body size and their postulated interaction are just beginning to be elucidated. The heritability of bone quantity and its relationship to components of body size were therefore investigated using segregation analysis applied to a large pedigreed nonhuman primate (Macaca nemestrina) breeding colony. The colony consisted of 216 females and 16 males with uniform dietary histories, environmental conditions, and rearing of offspring apart from the mother to minimize familial aggregation. Bone quantity (bone mineral content and spinal areal density) was measured by dual-energy X-ray absorptiometry (DXA). Size included measures of body mass, length, breadth, and a composite index. Body mass was determined from both body weight and lean body mass by DXA. Length was assessed by measuring trunk and thigh lengths, and breadth by measuring chest circumference and bitrochanteric width. A composite index of size was also calculated from a linear function of trunk and thigh lengths, chest circumference and bitrochanteric width, and lean body mass. Traits of bone quantity and size were highly correlated (r = 0.56-0.96, p < 0.001). Significant (p < or = 0.03) univariate heritabilities were found for spine bone mineral density (SPBMD; h(2) = 0.66) and whole body bone mineral content (WBBMC; h(2) = 0.40) and size measures of length (trunk h(2) = 0.71, thigh h(2) = 0.65), breadth (bitrochanteric width h(2) = 0.31), lean body mass (LEAN; h(2) = 0.37), and the composite index of size (SIZE-PC, h(2) = 0.49) adjusted for demographic variables. The data were also subjected to an analysis of bivariate genetic correlations and factor analysis, both of which suggested a robust interaction between body size and bone quantity. Bivariate genetic correlations between body size and the bone quantities WBBMC, SBMD, and spine bone mineral content (SPBMC) were high (e.g., using LEAN as a measure of size, r = 0.57, 0.41, and 0.57, respectively). Factor analysis showed that 80% of the phenotypic and 72% of the genetic variances of all traits were accounted for by a single factor, suggesting common genetic controls operative over bone quantity and size.

Three-dimensional analysis of nonhuman primate trabecular architecture using micro-computed tomography

Until recently, detailed analyses of the architecture of nonhuman primate cancellous bone have not been possible due to a combination of methodological constraints, including poor resolution imaging or destructive protocols. The development of micro-computed tomography (microCT) and morphometric methods associated with this imaging modality offers anthropologists a new means to study the comparative architecture of cancellous bone. Specifically, microCT will allow anthropologists to investigate the relationship between locomotor behavior and trabecular structure. We conducted a preliminary study on the trabecular patterns in the proximal humerus and femur of Hylobates lar, Ateles paniscus, Macaca mulatta, and Papio anubis to investigate the quantitative differences in their trabecular architecture and evaluate the potential of microCT in anthropological inquiry. MicroCT allows the researcher to evaluate variables beyond simple two-dimensional orientations and radiographic densities. For example, this methodology facilitates the study of trabecular thickness and bone volume fraction using three-dimensional data. Results suggest that density-related parameters do not reliably differentiate suspensory-climbing species from quadrupedal species. However, preliminary results indicate that measurements of the degree of anisotropy, a measure of trabecular orientation uniformity, do distinguish suspensory-climbing taxa from more quadrupedal species. The microCT method is an advance over conventional radiography and medical CT because it can accurately resolve micron-sized struts that make up cancellous bone, and from these images a wide array of parameters that have been demonstrated to be related to cancellous bone mechanical properties can be measured. Methodological problems pertinent to any comparative microCT study of primate trabecular architecture are discussed.

Interplay of pregnancy, lactation, and hyperthyroidism leading to severe osteoporosis in a young woman

OBJECTIVE

To describe the case of a young woman who had severe osteoporosis due to the compounding effects of pregnancy, lactation, and hyperthyroidism and who had a presumed metastatic lesion in the lumbar spine.

METHODS

We present the clinical, pathologic, radiologic, and laboratory findings and describe the clinical course of our patient.

RESULTS

A 31-year-old Arabic woman was referred to the M. D. Anderson Cancer Center because of a lytic lesion in her lumbar spine, presumed to be metastatic deposits. She had a history of two consecutive pregnancies and intermittently treated hyperthyroidism. Our initial evaluation revealed that the patient had clinical and biochemical thyrotoxicosis, and we treated her with thionamides, corticosteroids, and radioiodine ablation. Radiologic studies disclosed a complex renal cyst that had increased uptake on a bone scan, which was highly suggestive of a primary malignant lesion. Ultimately, however, it proved benign on pathologic analysis after a left nephrectomy. Bone mineral density measurements identified severe osteoporosis (T-scores: lumbar spine, -3.3; right hip, -2.2; and left hip, -2.0), which had led to vertebral collapse and was misinterpreted as malignant metastatic disease. The bone mineral densities improved (+5 to +11% at the various sites) within 4 months after definitive treatment and cure of the hyperthyroidism.

CONCLUSION

The effect of pregnancies and prolonged lactation, in the milieu of other risk factors for bone depletion such as hyperthyroidism, may cause severe osteoporosis in a young patient. The resulting osteoporosis may manifest as a lesion suggestive of malignant metastatic involvement.