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

Relationship of serum sex steroid levels and bone turnover markers with bone mineral density in men and women: a key role for bioavailable estrogen

Estrogen (E) deficiency associated with the menopause is the major cause of bone loss in aging women. However, men also lose significant amounts of bone with age, but they do not have the equivalent of menopause, and serum total testosterone (T) and E levels decline only marginally with age in men. Thus, it has been difficult to attribute bone loss in aging men to either T or E deficiency. Here, we show in a population-based, age-stratified sample of 346 men, aged 23-90 yr, that serum total T and E (estradiol plus estrone) levels decreased over the life span by 30% and 12%, respectively, but bioavailable (or nonsex hormone-binding globulin-bound) T and E levels decreased by 64% and 47%, respectively. In these men and in a parallel cohort of 304 women, aged 21-94 yr, serum PTH increased 84% and 64% over the life span, and urinary N-telopeptide of type I collagen (NTx) excretion, a bone resorption marker, increased 77% and 80% between age 50-85 yr in the men and women, respectively. By univariate analyses, serum bioavailable T and E levels correlated positively with bone mineral density (BMD) at the total body, spine, proximal femur, and distal radius and negatively with urinary NTx excretion in men and women. Urinary NTx excretion was also negatively associated with BMD in both sexes. By multivariate analyses, however, serum bioavailable E level was the consistent independent predictor of BMD in both men and postmenopausal women. Thus, bioavailable E levels decline significantly with age and are important predictors of BMD in men as well as women. These studies suggest that in contrast to traditional belief, age-related bone loss may be the result of E deficiency not just in postmenopausal women, but also in men.

Osteoporosis in men

Osteoporosis in men has become better recognized as an important health problem, particularly in the aged. Nevertheless, the knowledge available remains limited and fragmentary. Many clinical decisions must be based on extrapolations from the more complete understanding of osteoporosis in women. Gender differences in the causation and manifestation of the disease are probable, and the following issues clearly require better definition: Pathomechanisms. What are the determinants of age-related bone loss and fractures? What is the nature of idiopathic osteoporosis? How do other medical conditions result in osteoporosis? Cost-effective strategies for disease detection. Strategies for the prevention and treatment of bone loss and for the prevention of fractures.

A unitary model for involutional osteoporosis: estrogen deficiency causes both type I and type II osteoporosis in postmenopausal women and contributes to bone loss in aging men

We propose here a new unitary model for the pathophysiology of involutional osteoporosis that identifies estrogen (E) deficiency as the cause of both the early, accelerated and the late, slow phases of bone loss in postmenopausal women and as a contributing cause of the continuous phase of bone loss in aging men. The accelerated phase in women is most apparent during the first decade after menopause, involves disproportionate loss of cancellous bone, and is mediated mainly by loss of the direct restraining effects of E on bone cell function. The ensuing slow phase continues throughout life in women, involves proportionate losses of cancellous and cortical bone, and is associated with progressive secondary hyperparathyroidism. This phase is mediated mainly by loss of E action on extraskeletal calcium homeostasis which results in net calcium wasting and increases in the level of dietary calcium intake required to maintain bone balance. Because elderly men have low circulating levels of both bioavailable E and bioavailable testosterone (T) and because recent data suggest that E is at least as important as T in determining bone mass in aging men, E deficiency may also contribute substantially to the continuous bone loss of aging men. In both genders, E deficiency increases bone resorption and may also impair a compensatory increase in bone formation. For the most part, this unitary model is well supported by observational and experimental data and provides plausible explanations to traditional objections to a unitary hypothesis.

Sex steroids and bone mass in older men. Positive associations with serum estrogens and negative associations with androgens

The purpose of this study was to determine whether bone density in older men was associated with serum sex steroids or sex hormone binding globulin (SHBG). Bone density and sex steroids were measured in men over age 65 at 6-mo intervals for an average of 2.1 yr. Bone density was significantly positively associated with greater serum E2 concentrations (+0.21 < r < +0.35; 0.01 < P < 0.05) at all skeletal sites. There were weak negative correlations between serum testosterone and bone density (-0.20 < r < -0.28; 0.03 < P < 0.10) at the spine and hip. SHBG was negatively associated only with bone density in the greater trochanter (r = -0.26, P < 0.05). Greater body weight was associated with lower serum testosterone and SHBG, and greater E2. Because of these associations, regression models which adjusted for age, body weight, and serum sex steroids were constructed; these accounted for 10-30% of the variability in bone density, and showed consistent, significant positive associations between bone density and serum E2 concentrations in men, even after adjustments for weight and SHBG. These data suggest that estrogens may play an important role in the development or maintenance of the male skeleton, much as is the case for the female skeleton. These data also indicate that, within the normal range, lower serum testosterone concentrations are not associated with low bone density in men.

Serum testosterone and its relation to bone mineral density and body composition in normal males

OBJECTIVE

Bone mineral density (BMD) declines with age in both men and women, predisposing the elderly to osteoporosis and fractures. Although there are extensive data about post-menopausal osteoporosis, there is relatively little information concerning the decrease in BMD with age in normal men, particularly the contribution of declining gonadal function with age to BMD. In the present study, we investigated the effect of age on the pituitary-gonadal axis in normal males and its relation to BMD and body composition.

SUBJECTS

Ninety healthy Thai males in the Bangkok Metropolitan area without a history of smoking or significant alcohol consumption were studied.

MEASUREMENTS

Serum testosterone (T), free testosterone (FT), LH and FSH were measured by radioimmunoassay in fasting blood samples obtained in the morning between 0600 and 1000 h. BMD at anteroposterior L2-L4, lateral L2-L4, femoral neck, femoral trochanter and Ward's triangle were determined by dual-energy X-ray absorptiometry.

RESULTS

There were significant declines with age in BMD at lateral L2-L4 (r = -0.37, P < 0.001), femoral neck (r = -0.49, P < 0.0001), Ward's triangle (r = -0.54, P < 0.0001) but not at anteroposterior L2-L4 or femoral trochanter. Serum FT (r = -0.56, P < 0.0001) but not T (r = -0.19, P = 0.07) decreased with age. Serum LH (r = 0.27, P < 0.001) and FSH (r = 0.4, P < 0.0001) increased with age suggesting a defect in gonadal androgen synthesis or possibly a secretion of bioinactive LH. Serum FT concentrations were significantly correlated to lateral L2-L4 (r = 0.27, P < 0.05), femoral neck (r = 0.48, P < 0.0001) and Ward's triangle (r = 0.50, P < 0.0001) BMD. After controlling for age, declining FT with age was still associated with a decrease in BMD in femoral neck (P < 0.05) and Ward's triangle (P < 0.05) but not in lateral L2-L4. The proportion of body fat increased with age (r = 0.3, P < 0.01). Decreased serum T, but not FT, was associated with increased body fat after age was taken into account (P < 0.0001).

CONCLUSIONS

There is a decline in serum free testosterone together with increases in LH and FSH with age in healthy males. The decrease in serum free testosterone is partially associated with the age-related decline in bone mineral density added to the effect of age at the femoral neck and Ward's triangle. Testosterone but not free testosterone is associated with age-related increase in body fat.

Androgens and bone

Androgen receptors are present at low densities in osteoblasts. Androgens are also metabolized in bone. (Non)aromatizable androgens probably induce proliferation of osteoblasts and differentiation. A direct effect of androgens on osteoclasts has not been demonstrated. Androgens may however inhibit bone resorption indirectly, by an inhibition of the recruitment of osteoclast precursors from bone marrow, by decreased secretion of interleukin-6 and/or prostaglandin E2, and/or by an increased sensitivity of marrow cells or osteoblasts for bone resorption stimulating factors such as PTH. The recent demonstration of androgen receptors in bone marrow stromal and osteoclast-like cells opens new perspectives in this respect. During puberty, androgens stimulate bone growth both directly and indirectly. Observations in androgen-resistant animals clearly demonstrated that the sexual dimorphism of bone depends on the presence of a functional androgen receptor. Optimal peak bone mass seems related to an appropriately timed androgen secretion. In adults, androgens are also involved in maintenance of the male skeleton. Androgen replacement may prevent further bone loss in hypogonadal men, however, it seems difficult to fully correct bone mass in these men.

Effect of age on bone density and bone turnover in men

OBJECTIVE

Little is known about the pattern of age-related bone loss in men, and although androgens are required for optimum bone mass it is not clear whether the fall in bone mass with age in men is related to falling androgens.

DESIGN

Cross-sectional measurement of bone density, at five sites, and markers of bone resorption and formation in 147 normal volunteers aged 20-83 years.

SUBJECTS

Healthy laboratory workers, hospital staff, their relatives, and husbands of women attending our osteoporosis clinic.

MEASUREMENTS

Forearm density (fat corrected), spine L2-L4, femoral neck, Ward's triangle and trochanter density; serum procollagen I C-terminal extension peptide, osteocalcin, bone alkaline phosphatase and collagen I C-terminal telopeptide; fasting urine hydroxyproline/creatinine, pyridinoline/creatinine and deoxy-pyridinoline/creatinine; and free androgen index (FAI), measured as serum testosterone/sex hormone binding globulin.

RESULTS

Bone loss accelerated at most sites after age 50. There was a significant fall in FAI from the third decade onwards. The levels of all bone markers fell with age.

CONCLUSIONS

Bone loss in men appears to accelerate from age 50 and is associated with decreased bone formation which may be associated with falling levels of free androgen.

Relations of endogenous anabolic hormones and physical activity to bone mineral density and lean body mass in elderly men

OBJECTIVE

It has been proposed that declining activities of the somatotrophic or gonadotrophic axes, or sedentary life style, are partial causes for geriatric losses of bone mineral density (BMD) and of lean body mass (LBM). The present study tested these hypotheses by determining, in both free-living and institutionalized elderly men, the correlations of bone mineral density (BMD), total body bone mineral content (TBBMC) and lean body mass (LBM) with the following predictor variables: age, body mass index, body weight, serum insulin-like growth factor I (IGF-I), serum testosterone, habitual physical activity and mobility.

SUBJECTS

Forty-nine independent, community-dwelling older men, and 49 men of similar age residing in two Veterans Administration extended care facilities. The age range was 58-95 years.

MEASUREMENTS

Serum IGF-I and testosterone were measured by radioimmunoassay. Habitual physical activity in the independent men and mobility in the institutionalized men were estimated by standard instruments. LBM and bone status at nine skeletal sites were determined by dual X-ray absorptiometry.

RESULTS

The BMD and TBBMC values of the free living men were 4-20% higher than those of the institutionalized men. In the independent old men, serum testosterone was the strongest predictor of BMD and TBBMC, while age was the only predictor of LBM. In the chronically institutionalized men, age, body weight and immobility were the strongest predictors of body composition, and testosterone was correlated only with femoral neck BMD.

CONCLUSIONS

In aging independent men, low levels of testosterone are associated with demineralization of the skeleton. Immobility and under-weight are associated with the osteopenia of old men residing in nursing homes. In this cross-sectional study of elderly men, there was no evidence of a relation of the somatotrophic axis to bone status or LBM, or of the gonadotrophic axis to LBM.

Ethnic and genetic differences in susceptibility to osteoporotic fractures

A plethora of investigations in recent years has demonstrated the occurrence of ethnic differences in bone mineral content, bone density and fracture rates. These findings indicate that genetic determinants exist both for bone development during growth and for bone loss during aging. Twin and parent-offspring studies have corroborated the existence of a hereditary component. It is most evident in the greater bone mass and lower fracture rate in blacks than in whites. Differences in bone mass between Asians and whites are less clear than between blacks and whites because of disparities in body size and other confounding factors. Black children and adults excrete less urinary calcium than whites on essentially the same diets and consequently retain more calcium in their skeletons. Better calcium retention is commensurate with the faster rate of bone growth of black children.

Effects of testosterone replacement therapy in old hypogonadal males: a preliminary study

OBJECTIVE

To examine the effects of testosterone administration to older hypogonadal males (bioavailable testosterone less than 70 ng/dL).

DESIGN

Alternate-case controlled trial.

SETTING

St. Louis University.

PATIENTS

Eight males (mean age 77.6 +/- 2.3 years) who received testosterone and six males (mean age 76 +/- 2.3 years) who served as controls. Selected from alumni of the SHEP trial and attendees at the St. Louis University Impotence Clinic.

INTERVENTIONS

Testosterone enanthate (200 mg/mL) was administered intramuscularly to the treatment group every 2 weeks for 3 months.

MEASUREMENTS

Serum testosterone, bioavailable testosterone and estradiol, weight, % body fat, right hand muscle strength, balance, cholesterol, HDL-cholesterol, hematocrit, BUN, creatinine, albumin, calcium, PTH, 25(OH) vitamin D, 1,25(OH)2 vitamin D, osteocalcin, prostate-specific antigen, and fructosamine.

RESULTS

Males who received testosterone had a significant increase in testosterone and bioavailable testosterone concentration, hematocrit, right hand muscle strength and osteocalcin concentration. They had a decrease in cholesterol (without a change in HDL-cholesterol) levels and decreased BUN/Creatinine ratios.

CONCLUSION

These preliminary findings support the need for long term studies of testosterone therapy in older hypogonadal males.

Sex hormones and bone mineral density in elderly men

The aim of this study was to determine the relationships between sex hormones and bone mineral density (BMD) in older men. Community-dwelling men (n = 134, mean age (SD) 69.5 (3.1) years) were recruited from two general practices in Cambridge, UK. Plasma total testosterone and sex hormone binding globulin (SHBG) were assayed and a free androgen index (FAI) was derived as the ratio of total testosterone to SHBG (x 100). Spine and hip BMD were measured by dual energy x-ray absorptiometry using the Hologic QDR-1000. After adjusting for age and body mass index (BMI), the FAI correlated with femoral neck (r = 0.20, P = 0 0.03), intertrochanteric, trochanteric and Ward's Triangle BMD (r = 0.22, P = 0.01). Analysis of variance, with adjustment for age and BMI, showed a progressive upward trend of hip BMD with increasing quartiles of FAI. The findings suggest that free testosterone plays a role in determining bone mineral density in older men.

Lack of association between free testosterone and bone density separate from age in elderly males

It is unclear what proportion of the variance in bone density in elderly males is accounted for by testosterone status. We studied 112 ambulatory, elderly volunteers (mean age 71.7 years) and determined free testosterone (FT), as well as bone density measurements by photon absorptiometry at multiple sites. Our studies of 35 of these subjects 4 years later included morning FT and dual energy X-ray absorptiometry. There were no significant correlations between FT and bone density at multiple scanning sites with the effects of age partialed out. We suspect that our inability to detect a significant effect of FT on bone density was related to the relative strength of other determinants of bone density, as well as to the fact that FT values are far more dynamic than bone density.

Prolonged treatment with finasteride (a 5 alpha-reductase inhibitor) does not affect bone density and metabolism

OBJECTIVE

Since it is not clear whether testosterone or dihydrotestosterone is the active hormone in bone metabolism, we wished to assess the effect of finasteride, a 5 alpha-reductase inhibitor, or vertebral bone mineral density and parameters of bone and mineral metabolism.

DESIGN

Patients were treated in a randomized, double-blind controlled study with either placebo, 1 or 5 mg/day finasteride.

PATIENTS

Twenty-three men with benign prostatic hyperplasia (BPH) were included in this study; eight received placebo, seven were allocated to treatment with 1 mg/day, and eight to 5 mg/day finasteride for 12 months.

MEASUREMENTS

Vertebral bone mineral density was measured at the lumbar spine by dual energy X-ray bone densitometry. Serum calcium, phosphorus, parathyroid hormone, osteocalcin and vitamin D metabolites were measured regularly. Urinary calcium and creatinine excretion were monitored as well.

RESULTS

Finasteride caused a significant decrease in serum dihydrotestosterone after 6 and 12 months, but no effect on serum testosterone. Vertebral bone mineral density remained unaltered. None of the other parameters monitored were affected except for a small unexplained increase in 1.25-dihydroxyvitamin D in the group receiving 5 mg finasteride/day.

CONCLUSIONS

Testosterone is probably the active hormone in bone metabolism. However, oestradiol, the product of testosterone aromatization (which remains unaltered under finasteride) may yet be another possible responsible steroid in the maintenance of bone density. We can also not rule out that the small amount of dihydrotestosterone remaining under finasteride administration is sufficient for maintaining normal bone metabolism.

Does hypogonadism contribute to the occurrence of a minimal trauma hip fracture in elderly men?

The risk of MTHF in hypogonadal elderly men was investigated with a case-control model. Cases and controls were selected from males age 65 years and older residing in the 120-bed McGuire Veterans Affairs Medical Center Nursing Home Care Unit over a 5-day interval. Historical data and serum free testosterone (fTe) were available on 17 subjects with MTHF and 61 controls. When groups were compared for differences in age, race, alcohol abuse, cigarette abuse, and diseases or drugs that may be associated with MTHF, only race was significantly different. Although 25.6% of residents were black, 100% of MTHF subjects were white (P = 0.004). Hypogonadism was defined as a random fTe less than 9 pg/mL (normal 9 to 46 pg/mL) and was found in 21 subjects (26.9%). Of cases with a MTHF, 58.8% were hypogonadal compared with only 18.0% of controls. Utilizing logistic regression, a highly significant association was found between hypogonadism and MTHF (P = 0.008), and using the odds ratio, subjects with hypogonadism were 6.5 times more likely to have a MTHF (95% CI 2.0 to 20.6). To adjust for race, the odds ratio was repeated excluding black subjects, and the results remained highly significant (4.6, 95% CI 1.3 to 16.2). We conclude that hypogonadal elderly white men may be at increased risk for MTHF.

An examination of research design effects on the association of testosterone and male aging: results of a meta-analysis

The study of testosterone is likely to be prominent in future epidemiological work on endocrine function and the clinical treatment of age-related diseases. Thus, understanding the hormonal changes involved in the normal male aging process will be critical. Using techniques of meta-analysis, the authors examined 88 published studies of the age-testosterone relation in men. These studies reported conflicting results: age-testosterone correlations ranged from -0.68 to +0.68. In cross-study comparisons, certain research design characteristics (e.g. time of day of blood sampling) and various sample characteristics (e.g. volunteers vs patients as subjects) were related to both mean testosterone level and the slope of the age-testosterone relation. For example, for subgroups of subjects that did not exclude ill men, the mean testosterone levels were low, and did not decline with age. Subgroups that included only healthy subjects, in contrast, had higher overall testosterone levels and showed a decline of testosterone with age. Implications of these results for design, analysis and reporting of future epidemiologic studies will be discussed. These results also illustrate the utility of meta-analysis for research with the aged.

Physiological and pharmacological regulation of biological calcification

Biological calcification is a highly regulated process which occurs in diverse species of microorganisms, plants, and animals. Calcification provides tissues with structural rigidity to function in support and protection, supplies the organism with a reservoir for physiologically important ions, and also serves in a variety of specialized functions. In the vertebrate skeleton, hydroxyapatite crystals are laid down on a backbone of type I collagen, with the process being controlled by a wide range of noncollagenous proteins present in the local surroundings. In bone, cells of the osteoblast lineage are responsible for the synthesis of the bone matrix and many of these regulatory proteins. Osteoclasts, on the other hand, are continually resorbing bone to both produce changes in bone shape and maintain skeletal integrity, and to establish the ionic environment needed by the organism. The proliferation, differentiation, and activity of these cells is regulated by a number of growth factors and hormones. While much has already been discovered over the past few years about the involvement of various regulators in the process of mineralization, the identification and functional characterization of these factors remains an area of intense investigation. As with any complex, biological system that is in a finely tuned equilibrium under normal conditions, problems can occur. An imbalance in the processes of formation and resorption can lead to calcification disorders, and the resultant diseases of the skeletal system have a major impact on human health. A number of pharmacological agents have been, and are being, investigated for their therapeutic potential to correct these defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of age and body weight on spine and femur bone mineral density in U.S. white men

Bone mineral density (BMD) was measured in normal white males using 153 Gd dual-photon absorptiometry. Measurements were made on the lumbar spine (n = 315) and on the proximal femur (n = 282) utilizing three regions of interest. There was a small but significant age-related decrease in spinal BMD (r = -0.11; -0.001 g/cm2 per year) and trochanteric BMD (r = 0.27; -0.002 g/cm2 per year). The BMD of the other femoral sites decreased more rapidly; the femoral neck (r = -0.58; -0.005 g/cm2 per year) and Ward's triangle (r = -0.69; -0.007 g/cm2 per year) declined by about 21 and 34%, respectively, from age 20 to age 70. These femoral BMD decreases were three to four times greater than those usually seen in the peripheral skeleton in males but less than the decreases of 25-30 and 40% in the femoral neck and Ward's triangle of white females. This pattern of aging bone loss may partially explain the paucity of spine fractures and the lower incidence of hip fractures in males versus females.