Clinical significance and pathogenesis of osteoporosis

Intraskeletal variability in bone mass

For methodological or other reasons, a variety of skeletal elements are analyzed and subsequently used as a basis for describing general bone loss and mass. However, bone loss and mass may not be uniform within and among skeletal elements of the same individual because of biomechanical factors. We test the hypothesis that a homogeneity in bone mass exists among skeletal elements of the same individual. Measures indicative of bone mass were calculated from the midshafts of six skeletal elements from the same individuals (N = 41). The extent of intraskeletal variability in bone mass (relative cortical area) was then examined for the entire sample, according to age, sex, and pathological status. The results of the analysis showed that all measures reflect a heterogeneity in bone mass (P </= 0.001). Specifically, differences were observed between the bones of the upper limb and those of the lower limb. Both sexes showed intraskeletal variability in bone mass, but the difference between the sexes is not significant (P = 0.509). When the sample is subdivided according to age, all groups show intraskeletal variability in bone mass, but the difference did not differ significantly among the groups (P = 0.217). However, significant differences in intraskeletal variability are observed between individuals below and above the age of 50. Pathological individuals show intraskeletal variability in bone mass, but the difference between the pathological and non-pathological groups is not significant (P = 0.095). These results indicate that the bone mass of any particular skeletal element is intricately tethered to its specific mechanical loading environment.

Hormone replacement therapy and urinary prostaglandins in postmenopausal women

The objective of the study was to observe the effects of hormone replacement therapy upon urinary prostaglandin E2 and prostaglandin F2 alpha levels in postmenopausal patients. A total number of 55 women were enrolled in this study and 15 premenopausal (PreM) healthy subjects constitute the control group. A total of 40 patients at least 12 months after their natural menopause were divided into two groups: 15 of them was not medicated hormone replacement therapy (which composed NRHRT group) while 25 of the rest, received conjugated estrogen (Premarin) 0.625 mg/day orally plus medroxyprogesterone acetate (Farlutal) 10 mg/day orally built up the RHRT group. PGE2 and PGF2 alpha levels were measured with PGE2 [125I] and PGF2 alpha [3H] RIA kits. Statistical significance was analyzed by Student's t-test for impaired data. NRHRT and RHRT patients had had increased urinary PGE2 levels when compared with PreM (P < 0.001). HRT caused a significant decrease in PGE2 levels in menopausal women (P < 0.001). Urinary PGF2 alpha values of NRHRT and RHRT were significantly lower (P < 0.001) in comparison with PreM group. There was no difference in PGF2 alpha values between two postmenopausal groups. HRT given to postmenopausal patients might have a positive impact on prostaglandins and therefore on bone turnover in a series of various mechanisms.

Calcium and osteoporosis

Calcium is an essential nutrient that is involved in most metabolic processes and the phosphate salts of which provide mechanical rigidity to the bones and teeth, where 99% of the body's calcium resides. The calcium in the skeleton has the additional role of acting as a reserve supply of calcium to meet the body's metabolic needs in states of calcium deficiency. Calcium deficiency is easily induced because of the obligatory losses of calcium via the bowel, kidneys, and skin. In growing animals, it may impair growth, delay consolidation of the skeleton, and in certain circumstances give rise to rickets but the latter is more often due to deficiency of vitamin D. In adult animals, calcium deficiency causes mobilization of bone and leads sooner or later to osteoporosis, i.e., a reduction in the "amount of bone in the bone" or apparent bone density. The effects of calcium deficiency and oophorectomy (ovariectomy) are additive. In humans, osteoporosis is a common feature of aging. Loss of bone starts in women at the time of the menopause and in men at about age 55 and leads to an increase in fracture rates in both sexes. Individual fracture risk is inversely related to bone density, which in turn is determined by the density achieved at maturity (peak bone density) and the subsequent rate of bone loss. At issue is whether either or both of these variables is related to calcium intake. The calcium requirement of adults may be defined as the mean calcium intake needed to preserve calcium balance, i.e., to meet the significant obligatory losses of calcium through the gastrointestinal tract, kidneys, and skin. The calcium allowance is the higher intake recommended for a population to allow for individual variation in the requirement. The mean requirement defined in this way, calculated from balance studies, is about 20 mmol (800 mg) a day on Western diets, implying an allowance of 25 mmol (1000 mg) or more. Corresponding requirements and allowances have been calculated for pregnancy and lactation and for children and adolescents, taking into account the additional needs of the fetus, of milk production, and of growth. There is a rise in obligatory calcium excretion at menopause, which increases the theoretical calcium requirement in postmenopausal women to about 25 mmol (1000 mg) and implies an allowance of perhaps 30 mmol (1200 mg) or even more if calcium absorption declines at the same time. At issue here, however, is whether menopausal changes in calcium metabolism are the cause or the result of postmenopausal bone loss. The first interpretation relies on evidence of a positive action of estrogen on the gastrointestinal absorption and renal tubular reabsorption of calcium; the latter interpretation relies on evidence of a direct inhibitory effect of estrogen on bone resorption. The calcium model for postmenopausal bone loss tends to be supported by the effect of calcium therapy. An analysis of the 20 major calcium trials in postmenopausal women reported in the last 20 years yielded a mean rate of bone loss of 1.00% per annum (p.a.) in the controls and 0.014% p.a. (NS) in the treated subjects (P < 0.001). However, trials in which calcium and estrogen have been directly compared have shown that the latter is generally more effective than calcium in that it produces a small, but often significant bone gain. This superiority of estrogen over calcium could be due to the former's dual action on calcium absorption and excretion or to a direct action of estrogen on bone itself. In older women, the importance of calcium intake is overshadowed by the strong association between vitamin D insufficiency and hip fracture. Whether this insufficiency arises primarily from lack of exposure to sunlight or to a progressive failure to activate the vitamin D precursor in the skin or both is uncertain but it is compounded by a general decline in dietary vitamin D intake with age. The biological effect is probably an impairment of calcium absorption and c

Craniomandibular disorders and skeletal mineral status

Values for bone mineral density of the femoral neck and lumbar spine were determined by dual-energy x-ray absorptiometry for 355 postmenopausal women 48 to 56 years of age. The bone mineral density in three regions of the mandible was measured by quantitative computed tomography for 77 of the 355 women. Existing symptoms of craniomandibular dysfunction were recorded in both an anamnestic inquiry and a clinical examination. The purpose of this study was to determine whether the bone mineral density of the skeleton and mandible is associated with symptoms of craniomandibular dysfunctions. The results suggest that the habits and conditions that provoke development of general bone loss in the skeleton may disturb the functional harmony of the masticatory system and, thus, increase the possibility for craniomandibular disorders (CMD).

Resistance of the maxillary ridge to occlusal trauma

Histories and clinical evaluations were obtained from 230 postmenopausal women aged 48 to 56 years to determine whether the alveolar height in the edentulous anterior region of the maxillae is adversely affected by the presence of mandibular incisors. Many of these women lost their teeth in early adulthood. When all subjects were included, the height of the ridge in the anterior region of the maxillae was not significantly altered by presence of mandibular incisors. When the ridge height was compared among those who had been edentate in the maxillae for less than 30 years, the difference between dentate and edentate subjects was significant. This study indicates that the alveolar ridges in the anterior region of the maxillae where teeth were extracted early in life during the rapid phase of bone metabolism are less disposed to bite trauma caused by the presence of the mandibular incisors than are individuals who lost their teeth in middle or old age.

Change in bone mass immediately before menopause

A group of 75 healthy women nearing menopause were entered into a longitudinal study of bone mass and bone cell function. All were at least 46 years, were still menstruating, and had premenopausal levels of follicle stimulating hormone (FSH) and estradiol (E2). Bone density measurements of the spine (dual-photon absorptiometry, DPA) and total-body (DPA) and forearm (single-photon absorptiometry, SPA) were made at 6 month intervals along with measurements of FSH and E2 over an average of 2.04 +/- 0.45 years. The annual rate of change in bone mass was determined for each individual by regressing the bone mass measurement at each site at the time of observation. The slopes were pooled, and the percentage annual change was calculated as the mean slope divided by the initial mean bone mass value. The mean rates of change in bone mass were calculated with and without weighting by length of observation. No meaningful differences in the results were seen in the weighted values compared to the unweighted values, and none of the sites showed a slope significantly different from zero. Demonstrated reproducibility and sample size provided sufficient power to detect annual weighted rates of change of 0.81% for spine BMC, 0.69% for spine BMD, 1.31% for forearm BMC, 1.55% for forearm BMC/BW, and 1.09% for total body bone mineral. We conclude that if changes in bone mineral are occurring in women at this age, they are substantially less than 1%/year for spine and not much more for the forearm or total skeleton.

Bone density, mineral content, and cortical index in patients with thalassemia major and the correlation to their bone fractures, blood transfusions, and treatment with desferrioxamine

In an attempt to explain the increased frequency of pathological fractures found in thalassemia major patients, we examined noninvasively several properties of bones in 17 patients. We found a significant decrease in the bone mineral content (BMC) and the bone density (BD) of both trabecular (34% and 4% diminution, respectively) and cortical bone (24% and 3% diminution, respectively), as compared with normal controls. We also found that metacarpal cortical indices (CI) were significantly lower in thalassemic patients as compared with normal controls (36% diminution). As expected, upper limb fractures were more frequent in those patients with greater bone diminution. Furthermore, the degree of bone diminution was greater in patients receiving fewer blood transfusions and shorter courses of desferrioxamine. Bone densitometry should probably be included in the comprehensive evaluation of thalassemia patients in order to help guide overall treatment.

The ovariectomized rat model of postmenopausal bone loss

An animal model of postmenopausal bone loss can be defined as a living animal in which spontaneous or induced bone loss due to ovarian hormone deficiency can be studied, and in which the characteristics of the bone loss and its sequalae resemble those found in postmenopausal women in one or more respects. Although in comparison to humans, the skeletal mass of rats remains stable for a protracted period during their lifespan, rats can be ovariectomized to make them sex-hormone deficient, and to stimulate the accelerated loss of bone that occurs in women following menopause. Ovariectomy induced bone loss in the rat and postmenopausal bone loss share many similar characteristics. These include: increased rate of bone turnover with resorption exceeding formation; and initial rapid phase of bone loss followed by a much slower phase; greater loss of cancellous than cortical bone; decreased intestinal absorption of calcium; some protection against bone loss by obesity; and similar skeletal response to therapy with estrogen, tamoxifen, bisphosphonates, parathyroid hormone, calcitonin and exercise. These wide-ranging similarities are strong evidence that the ovariectomized rat bone loss model is suitable for studying problems that are relevant to postmenopausal bone loss.

Influence of sex and age in the risk of urolithiasis--a biochemical evaluation in Indian subjects

Urinary lithogenic promoters and inhibitors were estimated in normal Indian men and women of young and old ages to understand the sex difference in the risk of stone disease. Young men displayed increased phosphate excretion and a higher mean calcium (both lithogenic promoters) and lower excretion of citrate (lithogenic inhibitor) compared to women of the same age indicating that young men are more at risk for calculous disease than women. In the older postmenopausal women, there was increased excretion of calcium and magnesium and a lower mean citrate than in the younger women suggesting that oestrogenic activity during reproductive years appears to offer protection against calculogenesis. This study indicates that sex differences exist in the excretion of lithogenic promoters and inhibitors which partly explain the difference in the incidence of urolithiasis between men and women.

Vertebral cortical bone mass measurement by a new quantitative computer tomography method: correlations with vertebral trabecular bone measurements

Previous studies comparing axial and appendicular skeleton have shown that trabecular bone loss is greater than cortical bone loss. However, whether the same difference exists between the trabecular and the cortical compartments of the vertebral body remains to be determined. In this study, we used quantitative computer tomography (QCT) to simultaneously measure the cortical rim of the vertebral body as well as trabecular bone. In 99 Caucasian women (mean age 53.8 +/- 13.0 years, range 26-79 years) we found a significant correlation between cortical mineral content (BMCC) and both single (SE) and dual energy (DE) trabecular mineral content (BMCT) (r = 0.62, P less than 0.0001 for both regressions). The cross-sectional rates of bone loss per year were 1.32%, 1.16%, and 0.59% for SE-BMCT, DE-BMCT, and BMCC, respectively. BMCC decreased at a rate that was 45-51% that of SE-BMCT and DE-BMCT, respectively. Our results indicate that (1) QCT may provide a useful means to selectively measure cortical density in vertebral bodies; (2) the decrease of cortical density over time in the spine appears to have been underestimated previously by extrapolation from appendicular bone measurements; (3) because measurements of the entire vertebral body (exclusive of the posterior elements) may provide information that is more representative of spine changes with age, a measurement that includes both areas might be more useful than one measuring only the trabecular region.

Does a single local absorptiometric bone measurement indicate the overall skeletal status? Implications for osteoporosis and osteoarthritis of the hip

Regional bone mineral content (BMC) and density (BMD) (head, arms, chest, spine, pelvis, legs) of a total body dual photon 153Gd absorptiometry (DPA) scan were measured in 20 healthy postmenopausal women, 27 postmenopausal women with hip fracture, and 17 postmenopausal women with osteoarthritis of the hip. In addition, local BMC and BMD were measured in the proximal and distal regions of the distal forearm (BMCprox, BMDprox, BMCdist, BMDdist) by single photon absorptiometry (SPA); and in the lumbar spine (BMCL2-L4 and BMDL2-L4) by 153Gd DPA. The overall impression was a reduction of bone mass in hip fracture patients compared with healthy controls and an increase in the bone mass of osteoarthritic patients. These results were valid using both regional values of the total body scan, and local forearm and lumbar spine measurements, and statistically significant using one-way analysis of variance. There were, however, also significant within-group between-region differences (one-way analysis of variance), showing that the bone mass of the pelvis and legs in hip fracture patients was more reduced than in the remaining skeleton; in osteoarthritic patients it was not increased but rather unchanged or slightly reduced. The differences between the level of the three local measurements (BMDprox BMDdist BMDL2-L4), on the one hand, and the level of the six regional BMD values, on the other hand, were investigated by the two-way analysis of variance: local measurements = rows; regional values = columns. This analysis showed that none of the three local measurements was statistically better than the other two in predicting the overall level of skeletal bone mass as judged by the six regional values. We conclude that serious osteoporotic bone loss has a generalized nature, however, with a tendency towards lower values in the regions affected by fracture (viz: low bone mass in the legs of femoral neck fracture patients). Osteoarthritis may be associated with a high bone mass in most areas, but low values in the affected regions. Local lumbar spine measurement of bone mass by DPA is not superior to local forearm measurement of bone mass by SPA in predicting the nature of overall osteoporotic or osteoarthritic bone change.

Hamann-Todd Collection aging studies: osteoporosis fracture syndrome

The study presents a retrospective analysis of distal radius, proximal femur, vertebral, and sacral fractures that occurred in 938 Hamann-Todd Collection skeletons. Individuals included in the investigation were retrieved from dissecting room cadavers in Cleveland, Ohio, between the years 1910 and 1940. Demographic analysis showed that the mean ages at death for blacks and whites included in the study were 41.9 and 53.8 years, respectively. Evaluations of fracture repair status were made for all fractures that were identified. Observations that document side of involvement and unilateral/bilateral distribution were made for distal radius and hip fractures. It was found that the age-, sex-, and race-related fracture patterns which characterize the early 20th century Hamann-Todd sample strongly correspond in distribution and magnitude to those seen in modern American and European urban industrial communities. The distal radius, hip, vertebral, and sacral fractures which were identified in individuals over 60 years of age appear to be a primary result of skeletal fragility due to age progressive bone loss. However, it is suggested that the early onset and high frequency of distal radius fractures seen in climacteric Caucasian women may be more directly due to accidental falls initiated by a greater frequency, intensity, and duration of vasomotor disturbances which are known to accompanay estrogen withdrawal in perimenopausal white females.

Excretion of pyridinium cross-links of collagen in ovariectomized rats as urinary markers for increased bone resorption

Groups of 19-day-old rats were ovariectomized or were given sham operations. Measurements in urine of the pyridinium cross-links of collagen, pyridinoline and deoxypyridinoline, 7 weeks after surgery showed significantly higher amounts of cross-links relative to creatinine in the ovariectomized groups compared with the controls. Analyses before and after acid hydrolysis of the urine revealed that the increased excretion was only as free cross-link with no change in the concentrations of the bound forms. The loss of trabecular bone in the ovariectomized group was confirmed by immunocytochemical staining with antibodies to type I collagen. There were no differences between the ovariectomized and control groups in the concentrations of cross-links in the tibial bone or the articular cartilage. Measurements of free pyridinoline and deoxypyridinoline in urine therefore appear to provide a good index of the increased bone resorption induced by estrogen deficiency.

Discriminative ability of total body bone-mineral measured by dual photon absorptiometry

We investigated the discriminative ability of total body bone-mineral expressed as the total body bone-density (TBBD) measured by dual photon absorptiometry (DPA) in 79 healthy premenopausal women, 27 healthy postmenopausal women, and 120 female osteoporotic fracture patients presenting with either Colles' fracture, vertebral fracture or femoral neck-fracture. TBBD was compared to the bone-mineral density of the lumbar spine (BMDspine) also measured by DPA, and to the bone-mineral content of the forearms (BMCforearm) measured by single photon absorptiometry (SPA). TBBD, BMDspine and BMCforearm showed that all the fracture patient groups had significantly reduced bone-mass. Using receiver operating characteristic (ROC) analysis, we found that TBBD had a tendency towards better discriminative ability than BMDspine or BMCforearm with regard to the discrimination between healthy premenopausal women and the three types of osteoporotic fractures (not significant in spinal fracture patients). BMCforearm had an intermediate position, whereas BMDspine had the smallest discriminative ability. TBBD also discriminated better between healthy postmenopausal women and hip-fracture patients than BMDspine or BMCforearm, whereas there was no significant difference between the three methods regarding the discrimination between the healthy postmenopausal women and the Colles' and spinal fracture patients. We conclude that the TBBD measurement by DPA has a discriminative potential which is better than the local spine or forearm measurements.

Isotope computed tomography using cone-beam geometry: a comparison of two reconstruction algorithms

A CT scanner has been constructed specifically to determine the three-dimensional distribution of bone mineral in the medullary cavities of the radius, ulna and femur. A source of x-rays (153Gd) and a multiwire proportional counter (MWPC) are mounted at opposite ends of a diameter of an annular mounting. The limb is placed on the axis of rotation of the annulus and a series of two-dimensional transmission projections are obtained at equal angular spacings over 360 degrees. The distribution of bone mineral is reconstructed from the projections either by the method of maximum entropy (ME) or by convolution and back projection (CBP). These two methods have been evaluated by reconstructing a single slice of a phantom, representing the forearm, from projections simulated by computer. With a clinically acceptable exposure time, the mean medullary densities of the ulna and radius were determined with systematic errors of less than 3.5% (ME) and 11% (CBP), although for the latter method of reconstruction the systematic error was reduced to less than 2% by increasing the number of views. The mean medullary densities of the ulna and radius were determined with precisions better than 2.5% (ME) and 3.5% (CBP).

Simple test of intestinal calcium absorption measured by stable strontium

A clinical test of intestinal calcium absorption has been developed using non-radioactive stable strontium as a calcium tracer. In nine elderly subjects there was a close correlation between the fractional absorption of strontium and radioactive calcium (45Ca) during a five hour period after the simultaneous oral administration of the two tracers. Comparable precision was achieved with each tracer in six subjects in whom the test was repeated after two weeks. The effect of food on strontium absorption was examined in a further 33 normal subjects (age 21-60 years), and the administration of the strontium with a standard breakfast was shown to reduce the variance at individual time points. A simplified test in which serum strontium concentration was measured four hours after the oral dose given with a standard breakfast was adopted as the routine procedure. The normal range (mean (2 SD], established over 97 tests in 53 patients, was 7.0-18.0% of the dose in the extracellular fluid. A further 30 patients with possible disorders of calcium absorption (10 with primary hyperparathyroidism and 20 with coeliac disease) were studied by this standard test. In both groups of patients the mean four hour strontium values were significantly different from normal. This standard strontium absorption test allows assessment of calcium absorption with sufficient sensitivity and precision to have a wide application in clinical practice.

Osteoporosis, falls, and age in fracture of the proximal femur

The relative importance of osteoporosis and risk of falling in causing hip fracture is not known. Femoral neck bone mass was measured in 708 elderly people, all of whom had fallen and injured a hip. Below 75 years of age there was a steep increase in relative risk of fracture with reduced bone mass, measured by Singh grade. Above that age the increase in risk was small, and neuromuscular responses which protect the skeleton against trauma may be more important than bone mass.

Marked decline in trabecular bone mineral content in healthy men with age: lack of association with sex steroid levels

To define the association of age-related changes in bone mineral content to gonadal function in normal men, we measured radial (largely cortical) and vertebral (largely trabecular) bone mineral content (BMC), testosterone (total and free), estrone and estradiol-17B levels in 62 healthy subjects, ages 30 to 92. Radial BMC fell 2 to 3.4% per decade but vertebral trabecular BMC declined more rapidly at 12% per decade. Of the sex steroids measured the only statistically significant change occurred in free testosterone levels which decreased with age (r = -.57, P less than .0001). Free testosterone levels correlated significantly with trabecular vertebral BMC (r = .458, P less than .0002) but not with bone mineral measures at the predominantly cortical radial sites. However, by multiple regression analysis free testosterone did not add to the effect of age on vertebral BMC. There were no associations of total testosterone, estrone, or estradiol levels to bone mineral content at any of the three sites measured in these healthy men. Age-related declines in male gonadal function do not appear to be of primary importance in male age-related bone loss.

Suppression of ovarian activity by Zoladex depot (ICI 118630), a long-acting luteinizing hormone releasing hormone agonist analogue

A long-acting LHRH agonist, Zoladex depot 3.6 mg, was administered as a monthly s.c. injection to seven premenopausal volunteers for a maximum of 6 months, starting in the luteal phase of the cycle. Transient stimulation of gonadotrophin release was observed 24 h after the initial depot, followed by sustained suppression of plasma LH, while FSH levels returned to the normal range. Plasma oestradiol concentrations fell to early follicular phase values within 14 d. Twice-weekly monitoring of urinary oestrone-3-glucuronide and pregnanediol demonstrated inhibition of ovulation and almost complete suppression of ovarian follicular activity throughout therapy. All the subjects became amenorrhoeic. Mean plasma testosterone concentrations were also significantly reduced while androstenedione remained within the pretreatment range. SHBG concentrations were not significantly reduced. After cessation of therapy, postovulatory menstruation occurred within 80 d of administration of the last depot.

Postmenopausal osteoporosis

Osteoporosis is a major public health problem, particularly for the postmenopausal woman. With the withdrawal of estrogen at menopause, bone resorption begins to exceed formation in remodeling cycles and bone mass is inexorably lost. Clearly, preventing postmenopausal osteoporosis is the aim of management. Individuals with risk factors for developing this condition should have noninvasive bone density determination and should be considered for preventive regimens. Therapeutic options for prevention include calcium, estrogen, and exercise. Once osteoporosis is established, therapeutic options may include those listed previously as well as fluoride and other modalities currently under investigation.

Age-related changes in bone mass in the senescence-accelerated mouse (SAM). SAM-R/3 and SAM-P/6 as new murine models for senile osteoporosis

Age-related changes of the femoral bone mass in several strains of the senescence-accelerated mouse (SAM) were investigated. Microdensitometrically, all strains exhibited essentially the same patterns of age changes, that is, bone mass corrected by the diameter of the shaft reached the peak value when the mice were 4 or 5 months of age and then fell linearly with age up to over 20 months of age. Two strains, SAM-R/3 and SAM-P/6, which originated from the same ancestry on pedigree, had a significantly lower peak bone mass than other strains (SAM-R/1, SAM-R/2, SAM-P/1, and SAM-P/2). On the other hand, the strains with a low peak bone mass had the same rate of decrease as other strains. Mineral and collagen contents per dry weight of bone showed little difference among the strains. Histologic studies of tibia, femur, and lumbar spine revealed that the osteopenia was not due to osteomalacia but, rather, to osteoporosis. The elderly mice in these two strains were prone to fracture, thus should be important models for study of senile osteoporosis seen clinically.

Are scintigrams of the spine useful in vertebral osteoporosis?

To determine whether technetium diphosphonate scintigraphy could be used to date vertebral crush fractures, serial scintigrams and radiographs were obtained on two groups of 27 osteoporotic patients. Although radiologically crushed vertebrae were significantly associated with areas of increased isotope uptake on the scintigrams (p less than 0.001), this did not depend on the age of the crush fracture. Some radiologically uncrushed vertebrae, particularly in the lumbar spine, also showed increased isotope uptake.

Oestrogens and bone metabolism: a hypothesis

The explanations so far proposed for the effects of oestrogens on bone metabolism in post-menopausal women have been based on the changes seen in calciotrophic hormones. However, we demonstrated in a previous study [6] that there is a decrease in the concentration of somatomedin (an insulin-like growth factor) and an increase in that of growth hormone (GH) in oestrogen-treated post-menopausal women. On the basis of those findings and the relevant data published in the literature, we advance a hypothesis to the effect that the bone-metabolism changes that occur in post-menopausal women following oestrogen replacement therapy come about via changes in serum somatomedin and growth hormone concentrations.

Bone density in women with spinal and hip fractures

Bone density in the lumbar spine and distal radius of 98 postmenopausal women was measured by quantitative computed tomography and in the distal radius by gamma ray attenuation. Nineteen had spinal fragility fractures, 30 had recent hip fractures while 49 were healthy control subjects. The trabecular bone density in spines of the control subjects showed a linear correlation with age corresponding to an annual decrease of 1 per cent and total decrease of 44 per cent between 46 and 86 years of age. Both patient groups had bone density reduction at the spine and peripheral measuring sites as compared with controls. In the distal radius, the reduction in bone density was of the same magnitude in both patients groups but in the spine, the reduction in patients with spinal fracture was more extensive than that in patients with hip fracture. Trabecular bone density in the distal radius and spine correlated in control and hip fracture patients, but not in spinal fracture patients. The results support the opinion that two forms of osteoporosis exist. One is characterised by excessive trabecular bone loss in the axial skeleton leading to spinal fractures; the second is due to equal extents of axial and peripheral osteopenia, found in connection with hip fractures.

Endometrial carcinogenesis and its relation to oestrogens

The epidemiological evidence suggesting an association between the administration of exogenous oestrogens and an increased risk of developing endometrial adenocarcinoma is critically reviewed and it is concluded that the case for oestrogens being a cause of endometrial cancer is proven. The benefits flowing from preventing postmenopausal osteoporosis by oestrogen replacement therapy are assessed and contrasted with the danger to life posed by endometrial adenocarcinoma: it is pointed out that the type of neoplasm developing in patients taking oestrogens is well differentiated, nonaggressive and easily cured, the survival rate being very high. The addition of progestational agents to the therapeutic regime may prevent the development of endometrial carcinoma but could introduce a risk of cardiovascular disease.

The influence of age on the morphology of trochanteric fracture

A series of 127 trochanteric femoral fractures was analyzed with respect to fracture type, age, and bone quality (osteoporosis). There was a continuous decrease in bone quantity (measured as femoral score) with age and a direct relation between bone quality and the severity of the pattern of the trochanteric fracture. The skeletal ageing process starts earlier in women. However, after the age of 85 years the process is more rapid in men. Consequently, the risk of sustaining a trochanteric fracture is greater in men than in women above this age. The increasing age of the population and the longer survival of the oldest people results in more unstable and more comminuted fractures, which have increased by a factor of nearly 3 during the past three decades.

Bone formation and resorption as the determinants of trabecular bone volume in normal and osteoporotic men

Trabecular bone volume, forming surface and percent surface resorption have been determined in iliac crest samples obtained post mortem from 43 young men and 49 elderly men and in biopsies obtained from 22 males with spinal osteoporosis. The mean bone volume was significantly lower in the old than in the young controls and significantly lower again in the osteoporotic cases. Forming surfaces were significantly lower in the old than the young controls but were not different as between old controls and cases of osteoporosis. Percent surface resorption was the same in young and old controls but significantly increased in the osteoporotics. Multiple regression analysis showed that trabecular bone volume was a significant positive function of forming surface and a significant inverse function of fractional surface resorption. Age-related (simple) osteoporosis in men appears to be due to reduced bone formation whereas pathological (accelerated) osteoporosis is due to increased bone resorption.

Evaluation of the role of calcitonin deficiency in ovariectomy-induced osteopenia

Studies were carried out in rats to examine the role of calcitonin deficiency in the pathogenesis of ovariectomy-induced osteopenia. The parathyroid glands of 80 female Wistar rats were autotransplanted to their thigh muscle and the animals divided into 4 groups. Group 1 rats were sham ovariectomized, and thyroidectomized to make them calcitonin deficient; Group 2 rats were thyroidectomized, and ovariectomized to make them deficient in ovarian hormones as well; Group 3 rats were sham thyroidectomized and sham ovariectomized, and Group 4 rats were sham thyroidectomized and ovariectomized. A fifth group of rats were unoperated upon and served as controls. Thyroidectomized animals were maintained on thyroxine replacement and 11 months after ovariectomy all the animals were bled, killed and their femurs dissected out. In both the thyroid intact and thyroidectomized animals, ovariectomy decreased femur density significantly (P less than 0.01). Similarly, ovariectomy resulted in a decrease in femur calcium (P less than 0.01) in both groups of animals, and in a significant decrease in serum calcitonin (P less than 0.05) in the thyroid intact animals. We conclude from these findings that ovarian hormone deficiency can cause bone loss independently of lowering circulating calcitonin levels.

Osteoporosis: an update on pathogenesis and treatment

Both hormonal and nonhormonal factors appear to contribute to bone loss in osteoporosis. Decreased estrogen production, not enough calcium and too much protein, phosphorus and caffeine in the diet all have a probable effect. Aims of treatment include giving symptomatic relief, rehabilitation, arresting further bone loss, increasing the useful bone mass and restoring damaged skeletal architecture where possible. Current treatment includes ensuring that the patient avoids excess protein and caffeine and has adequate calcium in her diet. Estrogen therapy is still subject to debate, but does seem to prevent bone loss if initiated within three to five years of menopause. Much research is currently being done on sodium fluoride, the only agent that appears actually able to produce new bone.

Changes in bone mineral content of the axial skeleton in relation to aging and the menopause. Results from a longitudinal population study of women in Gothenburg, Sweden

Patterns of bone loss in the axial skeleton have been studied in a sample of Swedish women participating in a longitudinal population study which was started in 1968. In 1976, the mineral content of the lumbar spine (predominantly trabecular bone) was measured in vivo in 130 women by dual photon absorptiometry. Premenopausal or recently postmenopausal women were compared with women of identical age who had been postmenopausal for a long time. The first group was found to have significantly higher values of bone mineral content. Five years later, in 1981, the same women were re-examined with identical techniques. A slight decrease in bone mineral content with age was found in postmenopausal women. The findings were mostly in agreement with those of the first cross-sectional study, with bigger differences in bone mineral content between women of different menstrual status than between women of different age. In addition, the lower values in women with early menopause compared to those with late menopause remained in spite of increasing age.

Changes in bone mineral density of the proximal femur and spine with aging. Differences between the postmenopausal and senile osteoporosis syndromes

We measured bone mineral density (BMD) of the proximal femur, lumbar spine, or both by dual photon absorptiometry in 205 normal volunteers (123 women and 82 men; age range 20 to 92 yr) and in 31 patients with hip fractures (26 women and 5 men; mean age, 78 yr). For normal women, the regression of BMD on age was negative and linear at each site; overall decrease during life was 58% in the femoral neck, 53% in the intertrochanteric region of the femur, and 42% in the lumbar spine. For normal men, the age regression was linear also; the rate of decrease in BMD was two-thirds of that in women for femoral neck and intertrochanteric femur but was only one-fourth of that in women for lumbar spine. This difference may explain why the female/male ratio is 2:1 for hip fractures but 8:1 for vertebral fractures. The standard deviation (Z-score) from the sex-specific age-adjusted normal mean in 26 women with hip fracture averaged -0.31 (P < 0.05) for the femoral neck, -0.53 (P < 0.01) for the intertrochanteric femur, and +0.24 (NS) for the lumbar spine; results were similar for 5 men with hip fractures. By contrast, for 27 additional women, ages 51-65 yr, with only nontraumatic vertebral fractures, the Z-score was -1.92 (P < 0.001) for the lumbar spine. Thus, contrary to the view that osteoporosis is a single age-related entity, our data suggest the existence of two distinct syndromes. One form, "postmenopausal osteoporosis," is characterized by excessive and disproportionate trabecular bone loss, involves a small subset of women in the early postmenopausal period, and is associated mainly with vertebral fractures. The other form, "senile osteoporosis," is characterized by proportionate loss of both cortical and trabecular bone, involves essentially the entire population of aging women and, to a lesser extent, aging men, and is associated with hip fractures or vertebral fractures or both.

Role of parathyroid hormone and 1,25-dihydroxyvitamin D3 in the development of osteopenia in oophorectomized rats

The effect of ovarian insufficiency on calcium metabolism has been thought to involve an increased bone resorptive effect of parathyroid hormone and possible impaired synthesis of 1,25-dihydroxyvitamin D3. In the present study a rat model allowing for controlled serum levels of parathyroid hormone and 1,25-dihydroxyvitamin D3 was used. Oophorectomy in this species is associated with increased serum levels of 1,25-dihydroxyvitamin D3 and decreased bone mass. Although thyroparathyroidectomy increased bone mass, an increased sensitivity of bone to parathyroid hormone in oophorectomized rats was not observed. Thus the development of the osteopenia did not seem to be related to increased parathyroid hormone sensitivity or to reduced levels of 1,25-dihydroxyvitamin D3. Exogenous 1,25-dihydroxyvitamin D3 increased bone mass in oophorectomized as well as intact rats. Intestinal calcium transport was increased by moderate doses of 1,25-dihydroxyvitamin D3. Intestinal calcium transport was also reduced by thyroparathyroidectomy and increased by the administration of parathyroid extract. A tendency for increased accumulation of 1,25-dihydroxyvitamin D3 in blood in oophorectomized rats has been noted. It is suggested that the tendency to hypercalcemia in ovarian-insufficient females given 1-hydroxylated vitamin D compounds may be related to a diminished metabolism of 1,25-dihydroxyvitamin D3.

Bone formation and resorption as the determinants of trabecular bone volume in postmenopausal osteoporosis

Histomorphometry has been applied to trabecular bone samples obtained post-mortem from young and old women without known bone disease and to bone biopsy specimens from patients with postmenopausal osteoporosis. Bone volume was significantly lower in the old than young controls and significantly lower again in the osteoporotics. The loss of bone with age associated with a rise in surface resorption but no change in forming surface, and the further loss in osteoporotics was associated with a further rise in resorption and a small non-significant fall in forming surfaces. It is suggested that trabecular bone volume is determined by the relation between total forming surface on the one hand and percent surface resorption on the other, and this relationship is expressed in mathematical terms. Age-related bone loss (simple osteoporosis) in women is accounted for by increased resorption, and accelerated osteoporosis is mainly due to a further increase in resorption.

Lack of metabolic bone disease in patients with fracture of the femoral neck

To examine the widely held belief that osteoporosis and osteomalacia are pathogenetic factors in femoral neck fracture, we compared such patients with vertebral fracture patients and controls. Cortical bone was measured in hand X-rays and cancellous bone in iliac crest biopsies, which were also used to assess osteoid, tetracycline and resorbing surface. The vertebral fracture patients were found to have a reduction of 53% and 41% in cancellous and cortical bone respectively compared to the controls, while in the much older femoral fracture patients the reductions were 19% and 16%. Three femoral fracture patients had mild osteomalacia from identifiable causes; a further one had fluorosis of bone and one had metastatic carcinoma; with the exception of these the osteoid covered surface of bone was less than in vertebral fracture patients and controls. We conclude that pathologic osteoporosis and osteomalacia are not major factors in the pathogenesis of femoral neck fractures, though the normal age related reduction in bone mass may contribute. There may be another age related factor weakening the femoral neck. It was also noted that when assessed by a sensitive histochemical technique for osteoclast identification, bone resorption was not increased in either of the fracture groups.

Quantitative bone assessments: applications and expectations

Although, with the newer and more sophisticated radiologic methods the precision of bone mass measurement has been greatly improved, it is still impossible to predict the imminence of osteoporotic fractures, for two main reasons. First, current radiologic methods measure bone mass accurately only in appendiceal bone (largely cortical and regularly shaped) and not in axial bone (largely trabecular and irregularly shaped). However, most clinically significant fractures occur in the axial skeleton and involve trabecular bone, which is more prone than cortical bone to resorptive losses. Second, because of large differences in body habitus, the normal range of bone densities varies widely in any cohort of the same sex and race. Thus, although bone density measurements cannot be used to predict osteoporotic fractures, they have an important application in monitoring changes in skeletal mass for therapeutic and prophylactic purposes.