Citations

Abstract Bone mass is purportedly reduced by an endogenous or exogenous excess of thyroid hormone or, perhaps, by calcitonin deficiency. Patients who have undergone thyroidectomy could be subject to all of these effects, yet their practical implications in terms of fracture risk are poorly defined. Interpretation is further hampered by the focus on women, where results may be influenced by involutional osteoporosis. Consequently, we assessed the potential for fractures among the 136 Rochester, Minnesota men who underwent thyroidectomy between 1935 and 1979, relative to a group of age-matched control men from the community. With 2194 person-years of follow-up in each group, survival free of any fracture of vertebra, proximal humerus, distal forearm, pelvis, or proximal femur was similar in the two groups (p = 0.23), and the relative risk of any of these fractures for thyroidectomized patients versus their controls was increased only 1.5-fold (95% CI, 0.7–3.2). The difference was entirely accounted for by a statistically significant excess of proximal femur fractures in the men with thyroidectomy. Risk factors for fractures among men with thyroidectomy included greater age at surgery, greater extent of surgery, and the presence of risk factors for secondary osteoporosis. Thus, thyroidectomy, performed mainly for adenoma or goiter, seems to have little overall influence on the risk of age-related fractures in men. However, the association with hip fractures requires further evaluation.

Abstract To assess the influence of bone turnover on bone density and fracture risk, we measured serum levels of osteocalcin (OC), bone alkaline phosphatase (BAP), and carboxy-terminal propeptide of type I procollagen (PICP), as well as 24-h urine levels of cross-linked N-telopeptides of type I collagen (NTx) and the free pyridinium cross-links, pyridinoline (Pyd) and deoxypyridinoline (Dpd), among 351 subjects recruited from an age-stratified random sample of Rochester, Minnesota women. PICP, NTx, and Dpd were negatively associated with age among the 138 premenopausal women. All of the biochemical markers were positively associated with age among the 213 postmenopausal women, and the prevalence of elevated turnover (>1 standard deviation [SD] above the premenopausal mean) varied from 9% (PICP) to 42% (Pyd). After adjusting for age, most of the markers were negatively correlated with bone mineral density (BMD) of the hip, spine, or forearm as measured by dual-energy X-ray absorptiometry, and women with osteoporosis were more likely to have high bone turnover. A history of osteoporotic fractures of the hip, spine, or distal forearm was associated with reduced hip BMD and with elevated Pyd. After adjusting for lower BMD and increased bone resorption, reduced bone formation as assessed by OC was also associated with prior osteoporotic fractures. These data indicate that a substantial subset of elderly women has elevated bone turnover, which appears to adversely influence BMD and fracture risk. Combined biochemical and BMD screening may provide better prediction of future fracture risk than BMD alone.

Abstract Osteoporotic fractures are a significant public health problem, resulting in substantial morbidity and mortality. Previous estimates of the economic burden of osteoporosis, however, have not fully accounted for the costs associated with treatment of nonhip fractures, minority populations, or men. Accordingly, the 1995 total direct medical expenditures for the treatment of osteoporotic fractures were estimated for all persons aged 45 years or older in the United States by age group, sex, race, type of fracture, and site of service (inpatient hospital, nursing home, and outpatient). Osteoporosis attribution probabilities were used to estimate the proportion of health service utilization and expenditures for fractures that resulted from osteoporosis. Health care expenditures attributable to osteoporotic fractures in 1995 were estimated at $13.8 billion, of which $10.3 billion (75.1%) was for the treatment of white women, $2.5 billion (18.4%) for white men, $0.7 billion (5.3%) for nonwhite women, and $0.2 billion (1.3%) for nonwhite men. Although the majority of U.S. health care expenditures for the treatment of osteoporotic fractures were for white women, one-fourth of the total was borne by other population subgroups. By site-of-service, $8.6 billion (62.4%) was spent for inpatient care, $3.9 billion (28.2%) for nursing home care, and $1.3 billion (9.4%) for outpatient services. Importantly, fractures at skeletal sites other than the hip accounted for 36.9% of the total attributed health care expenditures nationally. The contribution of nonhip fractures to the substantial morbidity and expenditures associated with osteoporosis has been underestimated by previous researchers.

Abstract To assess the cost-effectiveness of interventions to prevent osteoporosis, it is necessary to estimate total health care expenditures for the treatment of osteoporotic fractures. Resources utilized for the treatment of many diseases can be estimated from secondary databases using relevant diagnosis codes, but such codes do not indicate which fractures are osteoporotic in nature. Therefore, a panel of experts was convened to make judgments about the probabilities that fractures of different types might be related to osteoporosis according to patient age, gender, and race. A three-round Delphi process was applied to estimate the proportion of fractures related to osteoporosis (i.e., the osteoporosis attribution probabilities) in 72 categories comprised of four specific fracture types (hip, spine, forearm, all other sites combined) stratified by three age groups (45–64 years, 65–84 years, 85 years and older), three racial groups (white, black, all others), and both genders (female, male). It was estimated that at least 90% of all hip and spine fractures among elderly white women should be attributed to osteoporosis. Much smaller proportions of the other fractures were attributed to osteoporosis. Regardless of fracture type, attribution probabilities were less for men than women and generally less for non-whites than whites. These probabilities will be used to estimate the total direct medical costs associated with osteoporosis-related fractures in the United States.

Abstract To meet expectations for the participation of minority populations in research, we committed to enroll 140 minority subjects in addition to a random sample of Olmsted County, Minnesota residents (90% white) for a study of risk factors for age-related bone loss and fractures. We successfully enrolled 597 additional minority subjects but encountered specific problems with respect to identification of potential subjects, recruitment, obtaining informed consent, transportation to the study site, and collecting study data. These problems were resolved by observing the tenets of outreach to a diverse study population, namely (1) understand the target population; (2) establish explicit recruitment goals; (3) agree on research plans between study staff and minority communities; (4) continuously evaluate the recruitment process; and (5) maintain lines of communication. Success depended especially on the recruitment of cultural advisors from the different ethnic groups. These special efforts increased the recruitment cost substantially; the total expense of $122,000 for recruiting 550 Asian, Hispanic, and Somali subjects was almost 5-fold higher than the $26,000 required to recruit 699 mostly white study subjects from the population who were contacted by mail. Although it is not impossible to recruit minority subjects, investigators (and grant reviewers) should recognize that significant resources are required to gain access to ethnic communities for research. These results should contribute to more realistic budgets for recruiting minority subjects into clinical research studies.

Abstract Oncogenic osteomalacia (OOM) is associated with primitive mesenchymal tumors that secrete phosphaturic factors resulting in low serum concentrations of phosphate and calcitriol, phosphaturia, and defective bone mineralization. To identify overexpressed genes in these tumors, we compared gene expression profiles of tumors resected from patients with OOM and histologically similar control tumors using serial analysis of gene expression (SAGE). Three hundred and sixty-four genes were expressed at least twofold greater in OOM tumors compared with control tumors. A subset of 67 highly expressed genes underwent validation with an extended set of OOM and control tumors using array analysis or reverse-transcription polymerase chain reaction (RT-PCR). Ten of these validated genes were consistently overexpressed in all OOM tumors relative to control tumors. Strikingly, genes with roles in bone matrix formation, mineral ion transport, and bone mineralization were highly expressed in the OOM tumors.

Abstract The role of the IGFs and IGFBPs on age-related changes in BMD in adult men and women is not well understood. Studying an age-stratified community based sample of 344 men and 276 women, we found higher IGFBP-2 levels to be associated with lower BMD. IGFBP-2, which increases with age in both men and women, was the strongest, most consistent predictor of BMD among the IGF/IGFBPs studied. Introduction: Insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) are important regulators of tissue growth and metabolism, but their association with BMD in adult men and women is controversial. Materials and Methods: In an age-stratified, random sample of the community population, we examined the role of serum levels of IGF-I, IGF-II, and IGFBP-1, −2, and −3 on BMD of the proximal femur (total hip), lateral spine, midshaft, and ultradistal radius as measured by DXA. We explored the association before and after adjustment for potential confounders, including age, bioavailable estradiol and testosterone, sex hormone binding globulin (SHBG), and measures of total fat and skeletal muscle mass. Results: We studied 344 men (age, 23-90 years) and 276 women (age, 21-93 years; 166 postmenopausal) not on hormone replacement or oral contraceptives. In both men and women, IGF-I and IGFBP-3 levels fell with advancing age, whereas IGFBP-2 levels tended to rise with age. There was an inverse association of IGFBP-2 with BMD at most skeletal sites in men and both premenopausal and postmenopausal women, whereas lower IGF-I and IGFBP-3 were associated with lower BMD in men and postmenopausal women only. Lower IGF-II was associated with lower BMD in men only. There were no associations between IGFBP-1 and BMD in either sex. After adjustment for age, in most cases, we found no further associations between IGF-I, IGF-II, or IGFBP-3 and BMD. In contrast, after age adjustment, higher IGFBP-2 remained a predictor of lower BMD in men and postmenopausal women at all sites except for the lateral spine (for men: r = −0.21, −0.20, and −0.19, all p < 0.001; and for postmenopausal women: r = −0.34, −0.24, and −0.25, all p < 0.01, for the total hip, midshaft, and ultradistal radius, respectively). IGFBP-2 remained an independent negative predictor of BMD in men, postmenopausal women, and all women combined after additional adjustment for bioavailable sex steroids, but not at all sites after adjustment for SHBG and muscle mass. In premenopausal women, IGFBP-2 had similar associations as seen in postmenopausal women, but they were weaker and not statistically robust. Conclusions: Among the IGF/IGFBPs in our study, IGFBP-2 was a key negative predictor of BMD among men and women, particularly postmenopausal women. Our findings suggest a potential role of the IGF/IGFBP system in regulating bone loss in aging men and women and identify a previously under-recognized, potentially deleterious role for IGFBP-2, a known inhibitor of IGF action that increases with age in both sexes. Whether the action of the IGF/IGFBP system on bone metabolism is mediated partly through its effects on muscle mass or SHBG deserves further study.

Abstract While severe primary hyperparathyroidism (HPT) is clearly associated with osteitis fibrosa cystica, it remains uncertain whether mild, asymptomatic primary HPT adversely affects the skeleton. Thus, we assessed the incidence of age-related fractures in a large, population-based inception cohort of 407 cases of primary HPT (93 men and 314 women) recognized during the 28-year period, 1965–1992. Fracture risk was assessed by comparing new fractures at each site to the number expected from gender- and age-specific fracture incidence rates for the general population (standardized incidence ratios, SIRs). These community patients with primary HPT mostly had mild disease (mean ± SD serum calcium, 10.9 ± 0.6 mg/dl). Altogether, 471 fractures occurred during 5766 person-years of follow-up. Overall fracture risk was significantly increased in these patients (SIR 1.3, 95% confidence interval [CI] 1.1–1.5). Primary HPT was associated with an increased risk of vertebral (SIR 3.2, 95% CI 2.5–4.0), distal forearm (SIR 2.2, 95% CI 1.6–2.9), rib (SIR 2.7, 95% CI 2.1–3.5), and pelvic fractures (SIR 2.1, 95% CI 1.1–3.5). The risk of proximal femur fractures was only marginally increased (SIR 1.4, 95% CI 1.0–2.0). By univariate analysis, increasing age and female gender were significant predictors of fracture risk, although higher serum calcium levels were also associated with increased fracture risk, and parathyroid surgery may have had a protective effect. By multivariate analysis, however, only age (relative hazard [RH] per 10-year increase, 1.6, 95% CI 1.4–1.9) and female gender (RH 2.3, 95% CI 1.2–4.1) remained significant independent predictors of fracture risk. Thus, primary HPT among unselected patients in the community is associated with a significant increase in the risk of vertebral, Colles', rib, and pelvic fractures. These data have important implications for the current trend to recommend nonsurgical management for patients with mild primary HPT.

Abstract In a population-based cross-sectional study, we examined effects of sex and age on bone microstructure at the wrist using high-resolution 3-D pQCT. Compared with women, men had thicker trabeculae in young adulthood and had less microstructural damage with aging. These findings may contribute to the virtual immunity of men to age-related increases in wrist fractures. Introduction: Although changes in bone microstructure contribute to fracture risk independently of BMD, it has not heretofore been possible to assess this noninvasively in population-based studies. Materials and Methods: We used high-resolution 3-D pQCT imaging (voxel size, 89 μm) to define, in a random sample of women (n = 324) and men (n = 278) 21–97 years of age, sex and age effects on bone microstructure at the wrist. Results: Relative to young women (age, 20–29 years), young men had greater trabecular bone volume/tissue volume (BV/TV; by 26%, p = 0.001) and trabecular thickness (TbTh; by 28%, p < 0.001) but similar values for trabecular number (TbN) and trabecular separation (TbSp). Between ages 20 and 90 years, cross-sectional decreases in BV/TV were similar in women (−27%) and in men (−26%), but whereas women had significant decreases in TbN (−13%) and increases in TbSp (+24%), these parameters had little net change over life in men (+7% and −2% for TbN and TbSp, respectively; p < 0.001 versus women). However, TbTh decreased to a greater extent in men (−24%) than in women (−18%; p = 0.010 versus men). Conclusions: Whereas decreases with age in trabecular BV/TV are similar in men and women, the structural basis for the decrease in trabecular volume is quite different between the sexes. Thus, over life, women undergo loss of trabeculae with an increase in TbSp, whereas men begin young adult life with thicker trabeculae and primarily sustain trabecular thinning with no net change in TbN or TbSp. Because decreases in TbN have been shown to have a much greater impact on bone strength compared with decreases in TbTh, these findings may help explain the lower life-long risk of fractures in men, and specifically, their virtual immunity to age-related increases in distal forearm fractures.