Sex steroids and bone

The association between depressive and anxiety symptoms and bone mineral density in the general population: the HUNT Study

BACKGROUND

Psychiatric disorders may be risk factors for reduced bone mineral density (BMD). Longitudinal evidence is limited and this is yet to be examined among community-dwelling adults with anxiety. We aimed to investigate the cross-sectional and longitudinal relationships between anxiety and depressive symptoms and BMD.

METHOD

This study examined data from the second Nord-Trondelag Health Study (1995-1997; 1194 men and 7842 women) and a follow-up conducted in 2001 (697 men and 2751 women). Symptomatology was ascertained using the Hospital Anxiety and Depression Scale and BMD was measured at the forearm using single-energy X-ray absorptiometry. Information on medication use and lifestyle was self-reported, and these, together with anthropometric measures were tested in multivariate analyses.

RESULTS

In men, adjusted BMD was 2.6% lower at the ultradistal forearm for those with depressive symptoms and 2.6% lower at the ultradistal and 2.0% lower at the distal forearm for those with anxiety symptoms. In women, adjusted BMD at the distal and ultradistal forearm was lower for heavier women with depressive symptoms but this relationship diminished with decreasing weight. Forearm BMD was similar for women with or without anxiety symptoms. Longitudinally, neither depressive nor anxiety symptoms were associated with bone loss over 4.6 years.

LIMITATIONS

Findings cannot be generalised to other skeletal sites and a longer follow-up period may be necessary to detect differences in bone loss.

CONCLUSIONS

These results indicate that depressive and anxiety symptoms are cross-sectionally associated with reduced BMD. These findings provide further evidence to support monitoring BMD in individuals diagnosed with psychiatric illness.

Direct transcriptional targets of sex steroid hormones in bone

The sex steroid hormones, androgens and estrogens, via their respective nuclear receptors, regulate bone mineral density in humans and mice. Very little is known about the direct targets of the androgen and estrogen receptors in bone cells. First, models of hormone and receptor deficiency in mouse and human bone are discussed. This review then focuses on the direct targets of the receptors in osteoblasts and osteoclasts. A direct target of a NR is defined here as a gene that is regulated by NR binding to the DNA (either through DNA binding or association with a DNA binding protein) at an enhancer or promoter of that gene. The experimental evidence that illustrates androgen and estrogen gene regulation in osteoblasts and osteoclasts will be summarized and compared with the phenotype of the hormones in vivo.

Bone metabolism and quality-of-life of postmenopausal women with invasive breast cancer receiving neoadjuvant hormonal therapy: sub-analyses from celecoxib anti-aromatase neoadjuvant (CAAN) trial

OBJECTIVE

Anti-aromatase therapy is important in the treatment of breast cancer in postmenopausal women but they have effects on the bone mineral density (BMD) and osteoporosis. Cyclooxygenase-2 (COX-2) inhibitors have been shown to be effective in chemoprevention in animal and clinical studies. A proof of principle study was performed to investigate the efficacy of combing anti-aromatase therapy (exemestane) and COX-2 inhibitors neoadjuvantly. The changes in the BMD, bone turnover proteins and quality-of-life (QoL) were analyzed and presented here.

METHOD

82 postmenopausal patients with histologically confirmed invasive hormone-sensitive breast cancers were included for the neoadjuvant therapy (NHT). 30 patients received exemestane (EXE) 25 mg daily and celecoxib (CXB) 400 mg twice daily (group A), 24 patients received EXE 25 mg daily (group B) and 28 patients received letrozole (LET) 2.5 mg daily (group C). The same assigned treatment was intended to continue for 2 years to study the changes in the bone metabolism. BMD of 48 patients were analyzed; 23 belongs to group A, 10 to group B and 15 to group C. The serum bone turnover proteins bone-specific alkaline phosphatase (BAP) and carboxyterminal crosslinked telopeptide of type I collagen (ICTP), were measured with commercially available test kits before treatment, 3 months and 15 months after treatment. Functional Assessment of Cancer Therapy core questionnaire (FACT-G) with its additional breast cancer subscale were performed at baseline, 4, 8, and 12 weeks after NHT.

RESULT

Difference between groups (p=0.007) for BMD at femur was significant. The changes of BMD in group B patients were significantly greater than patients in group A (p=0.011, CI=0.063-0.437), and group C (p=0.003, CI=0.146-0.620). The mean BAP increased from baseline in group B patients but decreased from baseline in group C patients at 3 months and 15 months. No statistical significance was found in the FACT-G scores and FACT-B scores among different groups at baseline, week 4, week 8 and week 12 after NHT. The Breast Cancer Subscale scores in group A patients were significantly higher than that of group C patients (p=0.021). After 4 weeks of NHT, negative changes of FACT-B and FACT-G scores were found in group B and C patients, but there were positive changes in group A patients. Significant differences of FACT-B score (p=0.008) and FACT-G score (p=0.019) were observed at that time point. Article from the Special issue on Targeted Inhibitors.

LC, a novel estrone-rhein hybrid compound, concurrently stimulates osteoprotegerin and inhibits receptor activator of NF-κB ligand (RANKL) and interleukin-6 production by human osteoblastic cells

Estrogen analogues are promising drugs for postmenopausal osteoporosis, but because of their possible side effects such as increased risk of cancer, estrogens which exert their estrogenic effects selectively on bone are desired. It has been shown that rhein inhibits osteoclast formation and bone resorption activity and has an antitumor role in several types of cancers. Having found that rhein had high affinity for the bone mineral, we synthesized estrone-rhein hybrid compounds and confirmed that one of these hybrid compounds, LC, exhibited a selective profile in the bone and prevented bone loss but had no effect on endometrium growth in ovariectomized rats. However, the mechanisms underlying its actions on human bone cells have not been well defined. Here we show that LC concurrently stimulates osteoprotegerin (OPG) and inhibits receptor activator of nuclear factor-κB ligand (RANKL) and Interleukin-6 (IL-6) production by human osteoblastic MG-63 cells containing two estrogen receptor (ER) isotypes. Treatment with the ER antagonist ICI 182,780 abrogates the above actions of LC on osteoblast-derived cells. Using small interfering double-stranded RNAs (siRNA) technology, we further demonstrate that the effects of LC on IL-6 production are mediated by both ERα and ERβ but those on OPG and RANKL expression primarily by ERα. Furthermore, we also demonstrate that LC functions at least partially through activation of the classic estrogen response element (ERE) pathway as well as Ras/MEK/ERK and PI3K/Akt signaling. The effect of LC on bone is due to not only its estrogenic activity but also action of its rhein moiety. Also, this compound shows much weaker effect on breast epithelial cell growth than that of estrone. Therefore, using rhein for conjugating compounds is a promising method of effectively targeting estrogens to the bone.

Bone regeneration and stem cells

This invited review covers research areas of central importance for orthopaedic and maxillofacial bone tissue repair, including normal fracture healing and healing problems, biomaterial scaffolds for tissue engineering, mesenchymal and foetal stem cells, effects of sex steroids on mesenchymal stem cells, use of platelet-rich plasma for tissue repair, osteogenesis and its molecular markers. A variety of cells in addition to stem cells, as well as advances in materials science to meet specific requirements for bone and soft tissue regeneration by addition of bioactive molecules, are discussed.

Terapia gênica para osteoporose

A osteoporose é considerada um dos problemas de saúde mais comuns e sérios da população idosa mundial. É uma doença crônica e progressiva, caracterizada pela diminuição da massa óssea e deterioração da microarquitetura do tecido ósseo. A terapia gênica representa uma nova abordagem para o tratamento da osteoporose e tem como princípio devolver a função comprometida pelo metabolismo. Esta revisão visa focar os trabalhos relevantes desenvolvidos nos últimos anos, disponibilizados nas bases de dados médicas, e que utilizaram a terapia gênica para o tratamento da osteoporose em modelos animais, bem como, as perspectivas futuras desta terapia. A maioria dos estudos utiliza os genes BMPs, PTH e OPG na tentativa de restabelecer a massa óssea. Apesar da carência de novas moléculas, todos os genes empregados nos estudos se mostraram eficientes no tratamento da doença. Os benefícios que a terapia gênica proporcionará aos pacientes no futuro devem contribuir substancialmente para o aumento na qualidade de vida dos idosos. Em breve, protocolos clínicos envolvendo humanos irão beneficiar os indivíduos com osteoporose.

Birth weight a negative determinant of whole body bone mineral apparent density in a group of adolescent boys

The aim of this study was to explore the relation between birth weight and bone mass in a group of adolescent boys. This study included 44 adolescent (aged 14-20yr) boys. Anthropometric characteristics (height and weight) were measured and birth weights were obtained from the obstetric records. Body composition was assessed by dual-energy X-ray absorptiometry (DXA). Bone mineral content (BMC) and bone mineral density (BMD) of the whole body (WB) and the lumbar spine (L2-L4) were also assessed by DXA. Calculations of the bone mineral apparent density (BMAD) were completed for the WB and at the lumbar spine (L2-L4). The expressions WB BMC/height and WB BMD/height were calculated to adjust for WB bone size. Birth weight was positively correlated to body weight (r=0.37; p<0.05), body mass index (r=0.38; p<0.01), body fat percentage (r=0.44; p<0.01), and negatively associated with WB BMAD (r=-0.46; p<0.01). In conclusion, this study suggests that birth weight is a positive determinant of body weight, body mass index, and body fat percent but a negative determinant of WB BMAD in adolescent boys.

Tissue-specific knockout of androgen receptor in mice

Androgen acting through the androgen receptor (AR) is known to be essential for male sexual differentiation and development. Using Cre-lox technology, we have generated the floxed AR mice, which have been bred with general or tissue-specific Cre expressing transgenic mice to knock out the AR gene in specific target cells. Our findings indicated that AR is required for sexual development and that loss of AR can have significant effects on many aspects of physiological functions and disease progression, such as immune function, metabolism, and tumorigenesis. Furthermore, our strategy can generate AR knockout (ARKO) in female mice, which allows researchers to study the AR function in the female. In brief, our floxed AR mouse model provides a powerful tool to study in vivo AR functions in selective tissues and cell types and has made possible several research breakthroughs in the field of endocrinology.

Physiological versus standard sex steroid replacement in young women with premature ovarian failure: effects on bone mass acquisition and turnover

BACKGROUND

The aim of this exploratory study was to establish whether we could improve skeletal health with a physiological regimen of SSR in young women with premature ovarian failure (POF).

PATIENTS AND METHODS

In an open-label randomized controlled crossover trial, 34 women with POF were randomized to 4-week cycles of pSSR (transdermal oestradiol, 100 μg daily for week 1, 150 μg for weeks 2-4; vaginal progesterone, 200 mg twice daily for weeks 3-4) or standard hormone replacement treatment (sHRT) (oral ethinyloestradiol 30 μg and 1·5 mg norethisterone daily for weeks 1-3, week 4 'pill-free') for 12 months. Bone mineral density (BMD) was measured by DEXA at study entry and after each 12-month treatment period. Blood samples for hormones and markers of bone formation (bone alkaline phosphatase, BALP and type I collagen N-terminal propeptide, PINP) and bone resorption (CrossLaps) were collected pre-/postwashout and after 3, 6 and 12 months of each treatment.

RESULTS

Eighteen women, mean 27 (range 19-39) years, completed the study. Both regimens caused similar suppression of LH and FSH. Mean baseline lumbar spine BMD z-score was -0·89 (95% CI -1·27 to -0·51) and increased by +0·17 (CI +0·07 to +0·27) in response to pSSR (P = 0·003), compared with +0·07 (CI -0·03 to +0·18) during standard HRT (P = 0·2). During pSSR, the increment in lumbar spine BMD z-score was related positively to oestradiol (r = +0·49, P = 0·04) and inversely to FSH (r = -0·65, P = 0·004). Bone formation markers, BALP and P1NP increased in the pSSR arm (anova P < 0·001) but decreased in the sHRT arm (P < 0·01). Both treatments suppressed the bone resorption marker, CrossLaps (P < 0·001).

CONCLUSION

We conclude that pSSR over 12 months has a beneficial affect on bone mass acquisition on the lumbar spine in women with POF, mediated by increased bone formation and decreased bone resorption.

Methods to quantify sex steroid hormones in bone: applications to the study of androgen ablation and administration

Bone may contain an intraskeletal reservoir of sex steroids that is capable of producing biological effects. The purposes of these experiments were to 1) establish and validate methods to extract and measure intraskeletal sex hormones, 2) compare serum and intraskeletal sex hormone abundance, and 3) determine the impact of testosterone-enanthate administration and orchiectomy on intraskeletal sex hormone concentrations. Tibiae from male F344 rats were crushed, suspended in an aqueous buffer, disrupted mechanically and sonically, extracted with organic solvents, dried, and reconstituted in assay buffer appropriate for measurement of testosterone, dihydrotestosterone, and estradiol by immunoassay. Prior to extraction, bone homogenate was spiked with [³H]testosterone, [³H]dihydrotestosterone, or [³H]estradiol, and >80% of each ³H-labeled sex hormone was recovered. Extracted bone samples were also assayed with and without known amounts of unlabeled sex hormones, and >97% of the expected hormone concentrations were measured. Administration of testosterone-enanthate increased intraskeletal testosterone 11-fold and intraskeletal dihydrotestosterone by 82% without altering intraskeletal estradiol (P < 0.01). Conversely, orchiectomy did not alter intraskeletal testosterone or estradiol but increased intraskeletal dihydrotestosterone by 39% (P < 0.05). In intact rats, intraskeletal testosterone and dihydrotestosterone were directionally higher than in serum, whereas intraskeletal estradiol was directionally lower than serum. Serum androgens were positively correlated with intraskeletal androgens (r = 0.74-0.96, P < 0.001); however, neither serum nor intraskeletal androgens nor serum estradiol were correlated with intraskeletal estradiol. We report the validation of a novel method for measuring intraskeletal sex hormones. Our findings demonstrate that the intraskeletal sex steroid reservoirs are modifiable and only partially influenced by circulating sex hormones.

Steroid hormone metabolizing enzymes in benign and malignant human bone tumors

IMPORTANCE IN THE FIELD: Primary bone tumors are considered as (sex steroid) hormone-dependent tumors. Osteosarcoma, osteoblastoma and bone cysts are preferentially found in males, while giant cell tumors are more common in females. Indeed, bone tumor development and progression are influenced by sex steroid hormones derived from in situ synthesis in bone cells.

AREAS COVERED IN THIS REVIEW

This review describes intracrine mechanisms for local formation of the biologically most active estrogen, 17beta-estradiol (E2), from circulating steroid precursors through the 'aromatase' (aromatization of androgens) and the 'sulfatase' (conversion of inactive estrone-sulfate) pathway.

WHAT THE READER WILL GAIN

The reader gains knowledge on both pathways and the enzymes, which contribute to the in situ availability of active hormones, namely 3beta-hydroxysteroid dehydrogenases, 17beta-hydroxysteroid dehydrogenases, aromatase, steroid sulfatases and sulfotransferases. An overview is given and the expression and function of these enzymes in bone tumors are discussed.

TAKE HOME MESSAGE

Knowledge on pathways for the in situ formation of E2 in bone cells may allow the identification of potential targets for i) novel endocrine therapeutic options in primary bone tumors and ii) future preventive interventions.

Late-life onset hypogonadism: a review

Increased longevity and population aging will increase the number of men with late-onset hypogonadism, a common condition that is often under diagnosed and under treated. The indication of testosterone replacement therapy (TRT) treatment requires the presence of low testosterone level and symptoms and signs of hypogonadism. Although there is a lack of large-scale, long-term studies assessing the benefits and risks of TRT in men with hypogonadism, reports indicate that TRT may produce a wide range of benefits that include improvement in libido and sexual function, bone density, muscle mass, body composition, mood, erythropoiesis, cognition, quality of life, and cardiovascular disease. Perhaps the most controversial area is the issue of risk, especially the possible stimulation of prostate cancer by testosterone, even though there is no evidence to support this risk. Other possible risks include worsening symptoms of benign prostatic hypertrophy, liver toxicity, hyperviscosity, erythrocytosis, worsening untreated sleep apnea, or severe heart failure. Despite this controversy, testosterone supplementation in the United States has increased substantially in the past several years. The physician should discuss with the patient the potential benefits and risks of TRT. This review discusses the benefits and risks of TRT.

Low-dose oral contraceptives in adolescents: how low can you go?

CONTEXT

The use of combined oral contraception (COC) before the accrual of peak bone mass in adolescents is common. Despite the tendency to prescribe lower ethinyl estradiol concentrations so as to reduce thromboembolic complications, concerns have developed as to whether low-dose COC provides sufficient estrogen supplementation for adequate adolescent bone development.

OBJECTIVE

This paper reviews the available literature on bone mineral density (BMD) and low-dose COC in adolescents in an effort to determine whether adult-oriented recommendations for the lowest tolerated estrogen dose should apply to adolescent populations.

DESIGN

A MEDLINE search of all English-language literature (1966 to January 2008) was performed using the terms "adolescent," "oral contraception," and "BMD." Bibliographies were reviewed to extract additional relevant sources. Articles were selected based on pertinence to BMD changes in association with low-dose (20 microg ethinyl estradiol) hormonal contraception with emphasis on adolescent study groups.

RESULTS

A limited number of studies examining 20-microg preparations in adolescents have demonstrated a significantly smaller mean percentage BMD acquisition in COC groups vs untreated controls. Bone mineral density decreases appeared to positively correlate with early gynecological age of first COC use and treatment duration.

CONCLUSIONS

Loss of bone mass as a result of hormonal contraceptive use may have serious long-term implications in the adolescent population, who have yet to achieve peak bone density. Both age at first COC use and cumulative estrogen dose appear to be important factors in determining skeletal development in adolescents. Further studies are warranted to inform specific prescribing practices for this population.

Osteoporosis: social and economic impact

The epidemiology of osteoporosis is reviewed, with a discussion of secular changes in incidence, geographical variation, and economic costs. The morbidity and mortality associated with hip, vertebral, and forearm fractures are outlined. The main pathogenetic factors contributing to age-related bone loss and osteoporosis are reviewed. Finally, there is a discussion of the recent advances in fracture risk prediction and the use of independent clinical risk factors to improve bone mineral density-based prediction.

Retaining Residual Ovarian Tissue following Ovarian Failure Has Limited Influence on Bone Loss in Aged Mice

Previous work showed that retaining residual ovarian tissue protects young mice from accelerated bone loss following ovarian failure. The present study was designed to determine whether this protection is also present in aged animals. Aged (9-12 months) C57BL/6Hsd female mice were divided into: CON (vehicle), VCD (160 mg/kg; 15d), or OVX (ovariectomized). Lumbar BMD was monitored by DXA and μCT used to assess vertebral microarchitecture. BMD was not different between VCD and CON at any time point but was lower (P < .05) than baseline, starting 1 month after ovarian failure in VCD and OVX mice. Following μCT analysis there were no differences between CON and VCD, but OVX mice had lower bone volume fraction, trabecular thickness, and a trend for decreased connectivity density. These findings provide evidence that retention of residual ovarian tissue may protect aged follicle-depleted mice from accelerated bone loss to a lesser extent than that observed in young mice.

The effects of hormonal contraceptives on bone turnover markers and bone health

Sex hormones are important regulators of bone metabolism. As hormonal contraceptives contain either oestrogens or progestins, or a combination thereof, it is conceivable that these widely used agents have an effect on bone metabolism and bone health. The main users of hormonal contraceptives, adolescent girls and young women, are still building bone and accruing bone mass and may therefore be particularly susceptible to the effects of hormonal contraceptives on bone. Despite these concerns, the effects of hormonal contraceptives on bone health are still poorly understood. As biochemical markers of bone turnover have been proven useful tools in the assessment and monitoring of bone metabolism, we reviewed the effects of combined and gestagen-only hormonal contraceptives on bone turnover markers and related effects on bone mineral density and fracture risk in premenopausal women, as documented in the literature until January 2009.

Birth weight is an independent determinant of whole body bone mineral content and bone mineral density in a group of Lebanese adolescent girls

The aim of this study was to explore the relation between birth weight and bone mass in a group of adolescent girls. This study included 40 post-menarchal adolescent (aged 13-20 years) girls. Anthropometric characteristics (height and weight) were measured and birth weights were obtained from the obstetric records. Body composition, bone mineral content (BMC) and bone mineral density (BMD) of the whole body (WB) were assessed by dual-energy X-ray absorptiometry (DXA). Calculations of the ratio BMC/height and of the bone mineral apparent density (BMAD) were completed for the WB. Birth weight was positively correlated to BMC and to the ratio BMC/height even after adjusting for weight and maturation index (years since menarche). Finally, birth weight was correlated to BMD even after adjusting for weight. In conclusion, this study suggests that birth weight is an independent determinant of whole body BMC and BMD in adolescent girls.

Effects of local melatonin application on implant osseointegration

PURPOSE

The aim of this study was to assess the effect of local melatonin administration on bone osseointegration around implants in rabbit tibiae.

MATERIAL AND METHODS

Ten female, 6-month-old New Zealand rabbits were randomly divided into two groups: the experimental group, where five rabbits were treated with local application of melatonin (3 mg) to implant sites when placed into the rabbit tibia, and the control group, those who where without additive materials. Four weeks later, animals were sacrificed; tibiae were dissected from soft tissues and fixed in buffered formaldehyde, and then included in methacrylate. Histological sections were performed to be studied under light microscopy and analyzed morphometrically to evaluate the amount of bone to implant contact (BIC), trabecular area density, and cortical area density. One-way analysis of variance test was used for statistical evaluation. p < .05 was considered to be significant.

RESULTS

Histological evaluation showed more trabecular reaction in the melatonin group. Morphometrical analysis showed a statistically significant increase in trabecular BIC in the melatonin group when compared with the control group (24.61% ± 2.87 vs 13.62% ± 1.44; p < .01). Cortical BIC was decreased in the melatonin group, without statistical significance (71.08 ± 3.63 vs 76.28 ± 2.57; p = 0.31). Trabecular area density was increased significantly in the melatonin group (8.68 ± 1.61 vs 4.02 ± 0.36; p < .05). Cortical area density was decreased significantly in the melatonin group (91.31 ± 1.6 vs 95.7 ± 0.5; p < .05).

CONCLUSION

Within the limitation of this animal study, local melatonin application at the time of implant placement might induce more trabecular bone at implant contact and higher trabecular area density.

Influence of the weight status on bone mineral content and bone mineral density in a group of Lebanese adolescent girls

AIM

The aim of this study was to determine the influence of being overweight on whole-body (WB) bone mineral content (BMC) and bone mineral density (BMD) in a group of Lebanese adolescent girls.

METHODS

This study included 32 overweight (BMI>25 kg/m2) adolescent girls (15.3+/-2.3 years old) and 24 maturation-matched (15.7+/-1.7 years old) controls (BMI<25 kg/m2). Bone mineral area (BMA), BMC, BMD at the WB and body composition (lean mass and fat mass) were assessed by dual-energy X-ray absorptiometry (DXA). Calculation of the ratio BMC/height and bone mineral apparent density (BMAD) were completed for the WB.

RESULTS

Expressed as crude values, BMA, BMC and the ratio BMC/height were higher in overweight adolescent girls compared to controls. After adjusting for body weight, there were no differences in BMC or in the ratio BMC/height between the two groups. However, BMA was lower in overweight girls compared to controls. After adjusting for either lean mass or fat mass, there were no significant differences between the two groups regarding these variables: BMC, BMA, BMD, BMC/height and BMAD.

CONCLUSION

This study suggests that the positive effect of overweight on BMC is due to body weight. In fact, the difference in BMC between the overweight and the control girls disappears after adjusting for body weight. In contrast, overweight girls have lower BMA compared to controls when values are adjusted to body weight.

Androgens and male aging: Current evidence of safety and efficacy

Many signs of aging, such as sexual dysfunction, visceral obesity, impaired bone and muscle strength, bear a close resemblance to features of hypogonadism in younger men. The statistical decline of serum testosterone in aging men is solidly documented. It has been presumed that the above features of aging are related to the concurrent decline of androgens, and that correction of the lower-than-normal circulating levels of testosterone will lead to improvement of symptoms of aging. But in essence, the pivotal question whether the age-related decline of testosterone must be viewed as hypogonadism, in the best case reversed by testosterone treatment, has not been definitively resolved. Studies in elderly men with lower-than-normal testosterone report improvement of features of the metabolic syndrome, bone mineral density, of mood and of sexual functioning. But as yet there is no definitive proof of the beneficial effects of restoring testosterone levels to normal in elderly men on clinical parameters. Few of these studies meet as yet rigorous standards of scientific enquiry: double-blind, placebo-controlled design of the study. The above applies also to the assessment of safety of testosterone administration to elderly men. There is so far no convincing evidence that testosterone is a main factor in the development of prostate cancer in elderly men and guidelines for monitoring the development of prostate disease have been developed. It is of note that there are presently no long-term safety data with regard to the prostate. Polycythemia is another potential complication of testosterone treatment. It is dose dependent and can be managed with dose adjustment.

Gender differences in bone turnover in 2-year-old Thoroughbreds

REASONS FOR PERFORMING STUDY

Injuries to the skeleton are a major cause of morbidity and mortality in racehorses and age, gender and season have all been shown to influence risk of injury.

OBJECTIVES

To use biochemical markers of bone cell activity to establish to whether cellular processes in bone underlie these described effects.

METHODS

Blood samples were collected monthly from 2-year-old horses in race training between November 1998 and September 1999. Mean age at the start of the study was 20 months (range 18-23 months), with no significant difference in average age between colts (n = 84) and fillies (n = 63). Three markers were measured; osteocalcin (OC, bone formation), the carboxyterminal cross-linked telopeptide of type I collagen (ICTP, bone resorption) and the carboxyterminal propeptide of type I collagen (PICP), which is less 'bone-specific' than the other 2 markers.

RESULTS

Colts had, on average, 3.62 ng/ml higher OC concentrations (P = 0.044) and 0.68 mg/l higher ICTP concentrations (P = 0.01) than fillies. The effect of gender was not statistically significant for PICP. However, in May, PICP concentrations were on average 157 mg/l higher in fillies than colts. There was no effect of age or season on marker concentrations.

CONCLUSIONS

This study has shown that there are gender differences in bone turnover markers in 2-year-old Thoroughbreds; however, age, within the limited range studied, did not have a significant effect on bone cell activity. Lower bone marker concentrations may reflect smaller bone size and/or earlier skeletal maturation in fillies. An increase in concentrations of PICP in fillies in spring and early summer may relect an influence of sex hormones on collagen turnover.

POTENTIAL RELEVANCE

Gender differences in bone cell activity in 2-year-old colts and fillies may influence bone's adaptive responses to training and risk of injury.

High prevalence of subtle and severe menstrual disturbances in exercising women: confirmation using daily hormone measures

BACKGROUND

The identification of subtle menstrual cycle disturbances requires daily hormone assessments. In contrast, the identification of severe menstrual disturbances, such as amenorrhea and oligomenorrhea, can be established by clinical observation. The primary purpose of this study was to determine the frequency of subtle menstrual disturbances, defined as luteal phase defects (LPD) or anovulation, in exercising women, with menstrual cycles of 26-35 days, who engage in a variety of sports, both recreational and competitive. Secondly, the prevalence of oligomenorrhea and amenorrhea was also determined via measurement of daily urinary ovarian steroids rather than self report alone.

METHODS

Menstrual status was documented by daily measurements of estrone and pregnanediol glucuronide and luteinizing hormone across two to three consecutive cycles and subsequently categorized as ovulatory (Ovul), LPD, anovulatory (Anov), oligomenorrheic (Oligo) and amenorrheic (Amen) in sedentary (Sed) and exercising (Ex) women.

RESULTS

Sed (n = 20) and Ex women (n = 67) were of similar (P > 0.05) age (26.3 +/- 0.8 years), weight (59.3 +/- 1.8 kg), body mass index (22.0 +/- 0.6 kg/m2), age of menarche (12.8 +/- 0.3 years) and gynecological maturity (13.4 +/- 0.9 years). The Sed group exercised less (P < 0.001) (96.7 +/- 39.1 versus 457.1 +/- 30.5 min/week) and had a lower peak oxygen uptake (34.4 +/- 1.4 versus 44.3 +/- 0.6 ml/kg/min) than the Ex group. Among the menstrual cycles studied in the Sed group, the prevalence of subtle menstrual disturbances was only 4.2% (2/48); 95.8% (46/48) of the observed menstrual cycles were ovulatory. This finding stands in stark contrast to that observed in the Ex group where only 50% (60/120) of the observed menstrual cycles were ovulatory and as many as 50% (60/120) were abnormal. Of the abnormal cycles in the Ex group, 29.2% (35/120) were classified as LPD (short, inadequate or both) and 20.8% (25/120) were classified as Anov. Among the cycles of Ex women with severe menstrual disturbances, 3.5% (3/86) of the cycles were Oligo and 33.7% (29/86) were Amen. No cycles of Sed women (0/20) displayed either Oligo or Amen.

CONCLUSIONS

This study suggests that approximately half of exercising women experience subtle menstrual disturbances, i.e. LPD and anovulation, and that one third of exercising women may be amenorrheic. Estimates of the prevalence of subtle menstrual disturbances in exercising women determined by the presence or absence of short or long cycles does not identify these disturbances. In light of known clinical consequences of menstrual disturbances, these findings underscore the lack of reliability of normal menstrual intervals and self report to infer menstrual status.

Dihydrotestosterone is a determinant of calcaneal bone mineral density in men

Male osteoporosis is an increasingly important health problem worldwide. Though androgen deficiency leads to bone loss in men, information on the relative contribution of aromatizable and non-aromatizable androgens in maintaining bone mineral density (BMD) and the mechanisms involved are unclear. This cross-sectional study was designed to explore the same. Hundred osteoporotic men with age matched normal were studied for serum levels of sex steroids, PTH, IGF system components, cytokines and bone turnover markers. Our findings show that serum DHT, IGF-I, IGF-II and IGFBP-3 levels were significantly decreased while IL-1beta and bone turnover markers were significantly increased in osteoporotic men compared to normal. Pearson correlation analysis revealed that serum DHT, IGF-I, IGF-II and IGFBP-3 levels were positively and strongly correlated with BMD, while serum IL-1beta levels were negatively correlated with BMD. Serum PTH, testosterone, estradiol, IGFBP-4, TNF-alpha, IL-4 and IFN-gamma levels were similar between the two groups. We observed that DHT levels significantly declined with age. However, the significant difference in DHT between the osteoporotic and normal groups is the same regardless of age. A multiple regression model adjusted for age demonstrated that DHT/BMD association is fairly stronger among those with osteoporosis than the normal. Our findings for the first time point out that DHT is an important determinant of BMD in men. Most importantly, the strong positive correlation of serum DHT with BMD offers new perspectives in understanding the role of non-aromatizable androgen in regulating bone metabolism in men, and might serve as a potential clinical marker in the diagnosis of male osteoporosis.

Body composition and bone mineral density in children with premature adrenarche and the association of LRP5 gene polymorphisms with bone mineral density

CONTEXT

Precocious increase in adrenal androgen production is the hallmark of premature adrenarche (PA). Adrenal androgens have anabolic properties.

OBJECTIVE

The objective of the study was to test whether body composition and bone mineral density (BMD) are altered in PA and study whether genetic variation in low-density lipoprotein receptor-related protein 5 (LRP5) affects BMD in PA.

DESIGN

This was a cross-sectional study.

SETTING

The study was conducted at a university hospital.

SUBJECTS AND MEASURES

The study included 126 prepubertal children (64 with PA, 10 boys; 62 non-PA controls, 10 boys). Femoral neck and lumbar spine areal and calculated volumetric BMD (dual energy X-ray absorptiometry), body composition (bioimpedance), serum 25-hydroxyvitamin D, and markers of bone turnover and calcium homeostasis were compared between the PA and control groups. Single-nucleotide polymorphisms of LRP5 were determined and associated with BMD.

RESULTS

Children with PA had higher femoral neck and lumbar spine BMD(areal) than the controls (Z-score 0.56 vs. -0.09, P < 0.001, and 0.20 vs. -0.31, P = 0.009, respectively). However, the mean BMDs did not differ significantly between the groups when adjusted for height or bone size. BMD(areal) correlated strongly with height sd score in both groups. Among the PA children, LRP5 single-nucleotide polymorphism E644E minor variant was associated with lower and F549F minor variant with higher BMD. Total body fat mass, fat percent, serum PTH, and alkaline phosphatase concentrations were higher and 25-hydroxyvitamin D lower in the PA group.

CONCLUSIONS

Prepubertal children with PA had higher BMD(areal) compared with healthy controls. This was mainly explained by their increased height. LRP5 polymorphisms may contribute to bone mass accrual in prepubertal PA children.

Effect of alcohol consumption on bone mineral density and hormonal parameters in physically active male soldiers

BACKGROUND

Previous studies on the influence of alcohol intake and smoking on bone mineral density (BMD) in men are inconsistent and the effect of these variables on BMD in physically active men is yet to be explored.

OBJECTIVE

To investigate the influence of alcohol intake and smoking on BMD in a cohort of males with well-defined lifestyle conditions.

DESIGN

Men from the armed forces (n=400) having uniform and defined routines were enrolled. BMD was measured by DXA and participants were grouped according to lifestyle variables. Hormonal parameters were measured by immunoassays.

RESULTS

Participants with intake of >24 g/wk of alcohol had significantly higher BMD at femur compared to non-alcohol consumers (p=0.0001) and a linear increase in mean femoral BMD over increasing categories of alcohol intake (p(trend)<0.0001) was observed. Smoking was negatively associated with femoral BMD. In multiple regression analysis, age, BMI, alcohol consumption and smoking were independent predictors of femoral BMD, explaining 10.6% variance. At lumbar spine, age, height and BMI were independent predictors, explaining 9.4% variance in BMD. The concentrations of total testosterone, free testosterone, bioavailable testosterone and PTH were low (p<0.0001) whereas estradiol (p=0.02), free and bioavailable estradiol (p<0.001) were high in alcohol consumers compared to non-consumers. In multiple regression analysis alcohol intake and height explained 5.5% variance in estradiol(.)

CONCLUSIONS

In physically active men with well-defined lifestyle conditions, alcohol consumption was associated with higher femoral BMD, the effect of alcohol is complex and is probably partly mediated by influencing the sex steroid levels.

The benefits and risks of testosterone replacement therapy: a review

Increased longevity and population aging will increase the number of men with late onset hypogonadism. It is a common condition, but often underdiagnosed and undertreated. The indication of testosterone-replacement therapy (TRT) treatment requires the presence of low testosterone level, and symptoms and signs of hypogonadism. Although controversy remains regarding indications for testosterone supplementation in aging men due to lack of large-scale, long-term studies assessing the benefits and risks of testosterone-replacement therapy in men, reports indicate that TRT may produce a wide range of benefits for men with hypogonadism that include improvement in libido and sexual function, bone density, muscle mass, body composition, mood, erythropoiesis, cognition, quality of life and cardiovascular disease. Perhaps the most controversial area is the issue of risk, especially possible stimulation of prostate cancer by testosterone, even though no evidence to support this risk exists. Other possible risks include worsening symptoms of benign prostatic hypertrophy, liver toxicity, hyperviscosity, erythrocytosis, worsening untreated sleep apnea or severe heart failure. Despite this controversy, testosterone supplementation in the United States has increased substantially over the past several years. The physician should discuss with the patient the potential benefits and risks of TRT. The purpose of this review is to discuss what is known and not known regarding the benefits and risks of TRT.

Glucocorticoids and the risk of osteoporosis

BACKGROUND

Glucocorticoid-induced osteoporosis (GIO) refers to a clinical condition in which a class of corticosteroids increases the susceptibility of bones to fracture. Numerous recent studies have improved our understanding of the underlying biology of this condition, whereas data from randomized controlled trials have provided clinicians with more options for prevention of GIO.

OBJECTIVE

To review the pathophysiology and epidemiology of GIO, as well as current pharmacologic treatment and prevention modalities available. To review the state of healthcare provider concordance with GIO prevention guidelines.

METHODS

Representative examples of various cellular and molecular processes underlying GIO were included, with an emphasis towards more recent discoveries. The data used to describe the epidemiology of GIO were derived from both randomized controlled studies and observational studies, framed through a discussion of known osteoporosis risk factors.

RESULTS/CONCLUSION

Progress has been made in clarifying the pathophysiologic mechanisms that result in GIO. Although the options for preventions and treatment of GIO continue to expand, provider compliance with preventive measures remains suboptimal.

Fourier X-ray scattering radiography yields bone structural information

PURPOSE

To characterize certain aspects of the microscopic structures of cortical and trabecular bone by using Fourier x-ray scattering imaging.

MATERIALS AND METHODS

Protocols approved by the National Institutes of Health Animal Care and Use Committee were used to examine ex vivo the hind limb of a rat and the toe of a pig. The Fourier x-ray scattering imaging technique involves the use of a grid mask to modulate the cone beam and Fourier spectral filters to isolate the harmonic images. The technique yields attenuation, scattering, and phase-contrast (PC) images from a single exposure. In the rat tibia cortical bone, the scattering signals from two orthogonal grid orientations were compared by using Wilcoxon signed rank tests. In the pig toe, the heterogeneity of scattering and PC signals was compared between trabecular and compact bone regions of uniform attenuation by using F tests.

RESULTS

In cortical bone, the scattering signal was significantly higher (P < 10(-15)) when the grid was parallel to the periosteal surface. Trabecular bone, as compared with cortical bone, appeared highly heterogeneous on the scattering (P < 10(-34)) and PC (P < 10(-27)) images.

CONCLUSION

The ordered alignment of the mineralized collagen fibrils in compact bone was reflected in the anisotropic scattering signal in this bone. In trabecular bone, the porosity of the mineralized matrix accounted for the granular pattern seen on the scattering and PC images.

Association of estrogen receptor beta gene polymorphisms with susceptibility to adolescent idiopathic scoliosis

STUDY DESIGN

A case-control study is presented.

OBJECTIVE

To investigate the association of estrogen receptor beta gene polymorphisms with susceptibility to adolescent idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Studies have shown that idiopathic scoliosis is related to genetic factors, such as XbaI site polymorphism of the estrogen receptor alpha gene. To our knowledge, however, the relationship of estrogen receptor beta gene polymorphisms and the individual susceptibility to idiopathic scoliosis has not been studied.

METHODS

This study included 218 patients with AIS and 140 healthy controls. Height, menarche status, curve pattern, Cobb angle, and Risser sign in female patients were recorded. Blood samples were taken from each subject by venipuncture. Genomic DNA was extracted from peripheral blood leukocytes using standard phenol/chloroform extraction. PCR products from amplification of genomic DNA from all individuals were analyzed using denaturing high-performance liquid chromatography. Samples with aberrant HPLC profiles were sequenced in both the forward and the reverse directions on an ABI 3100 automated sequencer. The chi test was used to determine the significant difference in genotype distribution between patients with AIS and the controls.

RESULTS

The frequency of CC genotype of the exon ØK (in reality 5' UTR OK-1)was significantly higher in patients than that in controls (P < 0.05). The C alleles appeared to be overrepresented in patients compared with controls (P < 0.05). Furthermore, the frequencies of CC genotypes in female patients whose height was > or =160 cm and Cobb angle was > or =30 degrees were higher than those whose height was <160 cm and Cobb angle was <30 degrees (P < 0.05). CONCLUSION.: The sites of the exon ØK polymorphisms of estrogen receptor beta gene may be associated with a susceptibility of AIS. Furthermore, the sites of the exon ØK polymorphism may be associated with the height and the curve severity of patients.

The effect of exemestane or tamoxifen on markers of bone turnover: results of a German sub-study of the Tamoxifen Exemestane Adjuvant Multicentre (TEAM) trial

Adjuvant treatment of breast cancer with aromatase inhibitors has been associated with increased bone loss. In this study, postmenopausal patients with oestrogen receptor positive breast cancer were randomised to exemestane for 5 years or tamoxifen for 2-2.5 years, followed by exemestane for 2-2.5 years. Levels of bone formation markers (bone specific alkaline phosphatase, amino terminal propeptide of type I procollagen, osteocalcin), and the bone resorption marker (carboxyterminal crosslinked telopeptide of type I collagen), were assessed at baseline and after 3, 6 and 12 months of treatment. Exemestane (n=78) resulted in increases from baseline in all bone turnover marker levels at all timepoints. In contrast, levels of all bone marker turnovers decreased with tamoxifen (n=83). Differences between tamoxifen and exemestane were statistically significant for all bone turnover markers at all timepoints. In conclusion, exemestane results in increases in markers of bone formation and resorption, while decreases are observed with tamoxifen.

Estrogen receptor beta as a mitochondrial vulnerability factor

We recently demonstrated mitochondrial localization of estrogen receptor beta (ERbeta). We herein confirm the mitochondrial localization of ERbeta by the loss of mitochondrial ERbeta immunoreactivity in ERbeta knockdown cells. A phenotype change characterized as an increase in resistance to oxidative stressors is associated with ERbeta knockdown. ERbeta knockdown results in a lower resting mitochondrial membrane potential (Deltapsim) and increase in resistance to hydrogen peroxide-induced Deltapsim depolarization in both immortal hippocampal cells and primary hippocampal neurons. ERbeta knockdown cells maintained ATP concentrations despite insults that compromise ATP production and produce less mitochondrial superoxide under oxidative stress. Furthermore, similar mitochondrial phenotype changes were identified in primary hippocampal neurons derived from ERbeta knock-out mice. These data demonstrate that ERbeta is expressed in mitochondria and function as a mitochondrial vulnerability factor involved in Deltapsim maintenance, potentially through a mitochondrial transcription dependent mechanism.

Associations between endogenous sex hormone levels and mammographic and bone densities in premenopausal women

PURPOSE

Mammographic breast and bone mineral densities (BMD) have been associated with luteal phase hormone concentrations in premenopausal women. We assessed the associations of breast and bone densities with follicular phase hormones and sex hormone binding globulin (SHBG) in premenopausal women, given that follicular phase hormones have been shown to be positively associated with premenopausal breast cancer risk.

METHODS

One hundred and ninety-two 40-45-year-old women provided a spot urine and/or blood sample during the follicular phase. Hormone and SHBG concentrations, and bone density were measured and routine mammograms were accessed and digitized to obtain breast density measures. Regression models were fit to assess the associations between hormones and SHBG, and breast and bone densities.

RESULTS

Positive associations were observed between percent breast density and SHBG (p trend = 0.02), as well as estradiol (p trend = 0.08), after controlling for body mass index (BMI), number of pregnancies, and breast feeding history. In addition, a statistically significant inverse association was observed between total testosterone and head BMD (p trend = 0.01), after controlling for BMI.

CONCLUSIONS

Associations were observed between breast and bone densities, and serum hormone concentrations during the follicular phase of the menstrual cycle.

Effects of menstrual cycle, oral contraception, and training on exercise-induced changes in circulating DHEA-sulphate and testosterone in young women

The objective of this study was to ascertain the effects of menstrual cycle, oral contraception, and training status on the exercise-induced changes in circulating DHEA-sulphate and testosterone in young women. Twenty-eight healthy women were assigned to an untrained group (n = 16) or a trained group (n = 12) depending on their training background. The untrained group was composed of nine oral contraceptive users (OC+) and seven eumenorrheic women (OC-). The trained group was composed of OC+ subjects only. All the OC+ subjects were taking the same low-dose oral contraception. Three laboratory sessions were organised in a randomised order: a prolonged exercise test until exhaustion, a short-term exhaustive exercise test, and a control session. Blood specimens were collected before, during and after the exercise tests and at the same time of the day during the control session. Basal circulating testosterone was significantly lower in trained as compared to untrained subjects. In all subjects, the prolonged exhaustive exercise induced a significant increase in circulating DHEA-s and testosterone. The short-term exercise induced a significant increase in circulating DHEA-s in untrained eumenorrheic and in trained OC users only. Menstrual phases in OC- did not influence the responses. It was found that exhaustive physical exercise induced an increase in circulating DHEA-s and testosterone in young women. Oral contraception may limit short-term exercise-induced changes.

Androgens and bone

Testosterone is the major gonadal sex steroid produced by the testes in men. Testosterone is also produced in smaller amounts by the ovaries in women. The adrenal glands produce the weaker androgens dehydroepiandrosterone, dehydroepiandrosterone sulfate, and androstenedione. These androgens collectively affect skeletal homeostasis throughout life in both men and women, particularly at puberty and during adult life. Because testosterone can be metabolized to estradiol by the aromatase enzyme, there has been controversy as to which gonadal sex steroid has the greater skeletal effect. The current evidence suggests that estradiol plays a greater role in maintenance of skeletal health than testosterone, but that androgens also have direct beneficial effects on bone. Supraphysiological levels of testosterone likely have similar effects on bone as lower levels via direct interaction with androgen receptors, as well as effects mediated by estrogen receptors after aromatization to estradiol. Whether high doses of synthetic, non-aromatizable androgens may, in fact, be detrimental to bone due to suppression of endogenous testosterone (and estrogen) levels is a potential concern that warrants further study.

Bone health in HIV infection

INTRODUCTION

Osteoporosis is among the chronic problems emerging as the human immunodeficiency virus (HIV)-positive population ages.

SOURCES OF DATA

We reviewed the English language bibliography using Pubmed 2.0, Web of Science and Embase for relevant abstracts and articles.

AREAS OF AGREEMENT

The prevalence of low bone mineral density (BMD) and fracture is increased in the HIV-positive population.

AREAS OF CONTROVERSY

The pathogenesis is multifactorial; there is some evidence that HIV infection is an independent risk factor and that highly active antiretroviral therapy has adverse skeletal effects.

GROWING POINTS

Physicians should routinely review the bone health of all HIV patients.

AREAS TIMELY FOR DEVELOPING RESEARCH

More studies of the mechanisms of bone loss, the skeletal effects of antiretroviral therapy and the therapeutic outcome of bone-protective therapy in HIV-positive individuals are needed.

Association between endogenous plasma hormone concentrations and fracture risk in men and women: the EPIC-Oxford prospective cohort study

Sex steroids have an important role in bone health, however previous studies on fracture risk have been carried out in older populations. The EPIC-Oxford study is a prospective cohort of men and women living in the UK. Five years after recruitment, participants self-reported previous fractures. Sex steroid concentrations (plasma estradiol, testosterone and sex hormone binding globulin) were measured in 436 cases (155 men, 46 premenopausal women and 235 postmenopausal women) with an incident fracture and 868 matched controls. Fracture risk was inversely related to concentrations of estradiol among men (RR for a doubling of estradiol 0.35, 95% CI 0.44-0.96) but there was no association between fracture risk and testosterone levels. There were no clear associations between fracture risk and hormone levels among postmenopausal women, however there was suggestion of an inverse association for both estradiol and testosterone as the RR in the highest compared with the lowest tertile for estradiol was 0.74 (95% CI 0.46, 1.18) and testosterone was 0.75 (95% CI 0.49, 1.16). Among premenopausal women fracture risk was inversely associated with levels of testosterone (RR for doubling of testosterone 0.46, 95% CI 0.26-0.81), with no association between estradiol and fracture risk. SHBG was not associated with risk of fracture among either men or women. In summary, this study finds evidence of an inverse association between endogenous estradiol and risk of fracture in men, and between endogenous testosterone and risk of fracture in premenopausal women but no clear associations among postmenopausal women.

IGF-I improved bone mineral density and body composition of weaver mutant mice

Our recent report on a parallel decrease in the body weights and serum IGF-I levels of weaver mice suggests that IGF-I's endocrine function may be impaired in neurodegenerative diseases. To further understand the overall effects of IGF-I deficiency on the postnatal growth, we measured bone mineral density (BMD), bone mineral content (BMC), lean body mass (LBM) and fat mass in male and female weaver mice and wild-type littermates on D21 (prepuberty), D45 (puberty), and D60 (postpuberty) using dual-energy X-ray absorptiometry (DEXA). In both male and female weaver mice, we found that the levels of circulating IGF-I paralleled those of BMD, BMC, and LBM, but not the fat mass. Male weaver mice have normal fat mass at all three ages studied, whereas female weaver mice showed a trend to increase their fat mass as they mature. To determine whether circulating IGF-I is a determinant of body composition, we crossbred IGF-I transgenic mice with homozygous weaver mice, which resulted in a significant increase in circulating IGF-I levels in both male and female weaver mice and normalization of their BMD, BMC and body weights. In summary, our results demonstrated that normal circulating IGF-I levels are important in maintaining BMD, BMC, and body composition in neurodegenerative diseases, such as hereditary cerebellar ataxia.

Supraphysiological testosterone enanthate administration prevents bone loss and augments bone strength in gonadectomized male and female rats

High-dose testosterone enanthate (TE) may prevent hypogonadism-induced osteopenia. For this study, 3-mo-old male and female Fisher SAS rats underwent sham surgery, gonadectomy (GX), or GX plus 28 days TE administration (7.0 mg/wk). GX reduced serum sex hormones (i.e., testosterone, dihydrotestosterone, and estradiol) (P < 0.05) in both sexes and bone concentrations of testosterone (males only), and estradiol (females only). GX also elevated urine deoxypyridinoline/creatinine in both sexes and serum osteocalcin (females only), findings that are consistent with high-turnover osteopenia. GX reduced cancellous bone volume (CBV) and increased osteoid surfaces in tibia of both sexes. GX males also experienced reduced trabecular number and width and increased trabecular separation, whereas GX females experienced increased osteoblast and osteoid surfaces. Bone biomechanical characteristics remained unaffected by GX, except that femoral stiffness was reduced in females. In contrast, TE administration to GX rats elevated serum and bone androgens to supraphysiological concentrations in both sexes but altered neither serum nor bone estradiol in males. Additionally, TE did not prevent GX-induced reductions in serum or bone estradiol in females. TE also reduced markers of high-turnover osteopenia in both sexes. In males, TE prevented GX-induced changes in trabecular number and separation, CBV, and osteoid surfaces while diminishing osteoblast and osteoclast surfaces; however, these changes were not fully prevented in females. In both sexes, TE increased femoral length and femoral maximal strength to above that of Sham and GX animals while preventing the loss of femoral stiffness in females. In conclusion, TE administration appears protective of cancellous bone in male rats and augments cortical bone strength in both sexes.