Androgens and bone: clinical implications for menopausal women

Hormonal therapy with estradiol and testosterone implants: bone protection?

OBJECTIVE

To assess bone mineral density (BMD) in postmenopausal women using estradiol and testosterone hormonal implants comparing to that of patients without hormonal therapy.

DESIGN OF THE STUDY

Sixty-one patients were followed in prospective cohort study separated in Group 1, 34 women using implants and Group 2, 27 women without implants and BMD assessment through Dual energy X-ray absorptiometry was conducted in the beginning of follow-up and after 1 year.

RESULTS

The average lumbar spine BMD in Group 1 was 1.123 ± 0.16 kg/m(2) and 1.144 ± 0.18 kg/m(2) after 1 year, p=0.39 and femur BMD was 0.922 ± 0.16 kg/m(2) and 0.957 ± 0.12 kg/m(2) after 1 year of treatment, p=0.076. In Group 2, the initial lumbar spine BMD average was 1.064 ± 0.2 kg/m(2) and after 1 year, 1.001 ± 0.23 kg/m(2), p=0.112 and femur BMD changed from 0.928 ± 0.14 kg/m(2) to 0.881 ± 0.15 kg/m(2) after 1 year, p=0.046.

CONCLUSION

BMD variance between the groups in the period of 1 year showed that the combination of estradiol and testosterone promoted bone protection in post menopausal women.

A longitudinal study of the effect of genistein on bone in two different murine models of diminished estrogen-producing capacity

This experiment was designed to assess the capacity of dietary genistein (GEN), to attenuate bone loss in ovariectomized (OVX) and ovary-intact VCD-treated mice. Pretreatment of mice with 4-vinylcyclohexene diepoxide (VCD) gradually and selectively destroys ovarian follicles whilst leaving ovarian androgen-producing cells largely intact. VCD induces a perimenopause-like condition prior to the onset of reproductive acyclicity. Sixteen-week-old C57BL/6J mice were randomized to five treatment groups: sham(SHM), OVX, SHM + VCD, OVX + GEN, and SHM + VCD + GEN. In vivo, blood samples were drawn for hormone and isoflavone analyses, estrous cycles were monitored, and X-ray imaging was performed to assess changes in bone parameters. Following sacrifice, ovaries were assessed histologically, bone microarchitecture was evaluated via microcomputed tomography, and bone mechanical properties were measured. Some effects of GEN were observed in OVX mice, but GEN effects were not able to be evaluated in VCD-treated mice due to the subtle diminution of bone during the 4 months of this experiment.

The relative effect of endogenous estradiol and androgens on menopausal bone loss: a longitudinal study

OBJECTIVE

The aim of this study was to assess the relative strength of the association of endogenous estradiol and androgens with bone loss at the lumbar spine and femoral neck during the menopausal transition.

DESIGN

A longitudinal study of a population-based cohort of 159 Australian-born women who at baseline had a mean age of 50.0 years (SD=2.4) and had menstruated in the prior 3 months. BMD was measured by dual-energy X-ray absorptiometry at the lumbar spine and femoral neck on up to three occasions.

RESULTS

Of the 159 participants, 50 had two BMD measurements and 109 had a third measure. The mean time between the first and final measures for the whole group was 39 months and at the time of the final measures 49% of the participants had become postmenopausal. The mean percentage change/year in lumbar spine BMD was -0.9% (95% CI, -1.1 to -0.6) and at the femoral neck, -0.5% (95% CI, -0.7 to -0.2). A highly significant association with estradiol at the final time point was found, whereas the contribution of estradiol at baseline was negligible. The variance explained by estradiol levels was 19% and 11% for change in BMD at the LS and FN, respectively. Excluding baseline estradiol values and using the average of change in BMD at the LS and FN, the final regression equation estimated that an estradiol level of 330 pmol/l (95% CI, 274 to 386) and 245 pmol/l (95% CI, 194 to 296) is required for preservation of LS and FN BMD, respectively. A stepwise linear regression model was used to assess the effect of age, BMI, estradiol, testosterone, DHEAS, SHBG, and free testosterone index on changes in BMD and found that only the final estradiol level had a significant association with change in BMD.

CONCLUSION

Endogenous estradiol was the only hormone among those investigated to have a significant effect on bone mineral density during the menopausal transition.

Bone anabolic effects of S-40503, a novel nonsteroidal selective androgen receptor modulator (SARM), in rat models of osteoporosis

A novel nonsteroidal androgen receptor (AR) binder, S-40503, was successfully generated in order to develop selective androgen receptor modulators (SARMs). We evaluated the binding specificity for nuclear receptors (NRs) and osteoanabolic activities of S-40503 in comparison with a natural nonaromatizable steroid, 5alpha-dihydrotestosterone (DHT). The compound preferentially bound to AR with nanomolar affinity among NRs. When S-40503 was administrated into orchiectomized (ORX) rats for 4 weeks, bone mineral density (BMD) of femur and muscle weight of levator ani were increased as markedly as DHT, but prostate weight was not elevated over the normal at any doses tested. In contrast, DHT administration caused about 1.5-fold increase in prostate weight. The reduced virilizing activity was clearly evident from the result that 4-week treatment of normal rats with S-40503 showed no enlargement of prostate. To confirm the bone anabolic effect, S-40503 was given to ovariectomized (OVX) rats for 2 months. The compound significantly increased the BMD and biomechanical strength of femoral cortical bone, whereas estrogen, anti-bone resorptive hormone, did not. The increase in periosteal mineral apposition rate (MAR) of the femur revealed direct bone formation activity of S-40503. It was unlikely that the osteoanabolic effect of the compound was attribute to the enhancement of muscle mass, because immobilized ORX rats treated with S-40503 showed a marked increase in BMD of tibial cortical bone without any actions on the surrounding muscle tissue. Collectively, our novel compound served as a prototype for SARMs, which had unique tissue selectivity with high potency for bone formation and lower impact upon sex accessory tissues.

Bone metabolism and the perimenopause overview, risk factors, screening, and osteoporosis preventive measures

In summary, FDA-approved therapies for prevention and treatment of osteoporosis are all antiresorptive agents. There are no approved therapies at this time that stimulate bone formation, although one such agent (PTH) is awaiting approval. Screening perimenopausal women at risk should identify osteopenic women early in the menopause before the accelerated bone loss of estrogen deficiency causes further irreversible erosion in bone density. The National Osteoporosis Foundation advocates initiating therapy to reduce fracture risk in postmenopausal women with T scores below -2 in the absence or factors and with T scores below -1.5 if other risk factors are present. Estrogen, alendronate, residronate, and raloxifene have all been shown to reduce the incidence of radiographic vertebral fractures in women at risk. Only alendronate and residronate have been shown in large randomized trials to reduce the incidence of nonvertebral fractures including hip fractures in women with postmenopausal osteoporosis. These antiresorptive therapies provide benefits above and beyond those of calcium and vitamin D alone. There is insufficient published evidence from randomized controlled trials convincingly to support a role for soy products, androgens, calcitonin, or fluoride in prevention of postmenopausal osteoporosis or reduction of fracture rates in women at risk.

Androgen supplementation in older women: too much hype, not enough data

Androgen supplementation in women has received enormous attention in the scientific and lay communities. That it enhances some aspects of cognitive function, sexual function, muscle mass, strength, and sense of well-being is not in question. What is not known is whether physiological testosterone replacement can improve health-related outcome in older women without its virilizing side effects. Although it is assumed that the testosterone dose-response relationship is different in women than in men and that clinically relevant outcomes on the above-mentioned effects can be achieved at lower testosterone doses, these assumptions have not been tested rigorously. Androgen deficiency has no clear-cut definition. Clinical features may include impaired sexual function, low energy, depression, and a total testosterone level of less than 15 ng/dL, the lower end of the normal range. Measurement of free testosterone is ideal, because it provides a better estimate of the biologically relevant fraction. It is not widely used in clinical practice, because some methods of measuring free testosterone assay are hampered by methodological difficulties. In marked contrast to the abrupt decline in estrogen and progesterone production at menopause, serum testosterone is lower in older women than in menstruating women, with the decline becoming apparent a decade before menopause. This article reviews testosterone's effects on sexual function, cognitive function, muscle mass, body composition, and immune function in postmenopausal women.

The impact of testosterone imbalance on depression and women's health

Women suffer more often from depression than males, indicating that hormones might be involved in the etiology of this disease. Low as well as high testosterone (T) levels are related to depression and well-being in women, T plasma levels correlate to depression in a parabolic curve: at about 0.4-0.6 ng/ml plasma free T a minimum of depression is detected. Lower levels are related to depression, osteoporosis, declining libido, dyspareunia and an increase in total body fat mass. Androgen levels in women decrease continuously to about 50% before menopause compared to a 20-year-old women. Androgen levels even decline 70% within 24 h when women undergo surgical removal of the ovaries. Conventional oral contraception or HRT cause a decline in androgens because of higher levels of SHBG. Hyperandrogenic states exist, like hirsutism, acne and polycystic ovary syndrome. Social research suggests high androgen levels cause aggressive behavior in men and women and as a consequence may cause depression. Higher androgen values are more pronounced at young ages and before and after delivery of a baby and might be responsible for the "baby blues". It was found that depression in pubertal girls correlated best with an increase in T levels in contrast to the common belief that "environmental factors" during the time of growing up might be responsible for emotional "up and downs". T replacement therapy might be useful in perimenopausal women suffering from hip obesity, also named gynoid obesity. Abdominal obesity in men and women is linked to type 2 diabetes and coronary heart diseases. Testosterone replacement therapy in hypoandrogenic postmenopausal women might not only protect against obesity but also reduce the risk of developing these diseases. Antiandrogenic progestins might be useful for women suffering from hyperandrogenic state in peri- and postmenopause. Individual dosing schemes balancing side effects and beneficial effects are absolutely necessary. Substantial interindividual variability in T plasma values exists, making it difficult to utilize them for diagnostic purposes. Therefore a "four-level-hormone classification scheme" was developed identifying when estradiol (E) and T levels are out of balance. (1) Low E-low T levels are correlated with osteoporosis, depression, and obesity; (2) high E-low T with obesity, decreased libido; (3) high T-low E levels with aggression, depression, increased libido, and substance abuse; (4) high E-high T with type II diabetes risk, breast cancer and cardiovascular risk. Testosterone delivery systems are needed where beneficial and negative effects can be balanced. Any woman diagnosed for osteoporosis should be questioned for symptoms of depression.

Role of estrogens in the management of postmenopausal bone loss

It is well known that estrogen deficiency is the major determinant of bone loss in postmenopausal women. Estrogen is important to the bone remodeling process through direct and indirect actions on bone cells. The largest clinical experience exists with estrogen therapy, demonstrating its successful prevention of osteoporosis as well as its positive influence on oral bone health, vasomotor and urogenital symptoms, and cardiovascular risk factors, which may not occur with other nonestrogen-based treatments. Compliance with HRT, however, is typically poor because of the potential side effects and possible increased risk of breast or endometrial cancer. Nevertheless, there is now evidence that lower doses of estrogens in elderly women may prevent bone loss while minimizing the side effects seen with higher doses of estrogen. Additionally, when adequate calcium, vitamin D, and exercise are used in combination with estrogen-based treatments, more positive increases occur in bone density. The benefits and risks of HRT must be assessed on a case-by-case basis, and the decision to use HRT is a matter for each patient in consultation with her physician. Estrogen-based therapy remains the treatment of choice for the prevention of osteoporosis in most postmenopausal women, and there may be a role for estrogen to play in the prevention of corticosteroid osteoporosis. Combination therapies using estrogen should probably be reserved for patients who continue to fracture on single therapy or should be used in patients who present initially with severe osteoporosis.

New approaches to the treatment of osteoporosis

Under physiological conditions, maintenance of skeletal mass is the result of a tightly coupled process of bone formation and bone resorption. Disease states, osteoporosis included, arise when this delicate balance is disrupted such as in menopause, when estrogen levels decrease dramatically corresponding with the cessation of ovarian function. Current therapies for the treatment of osteoporosis, including estrogen replacement therapy, selective estrogen receptor modulators and bisphosphonates, are primarily based on blunting the resorption component of bone homeostasis. Although selective estrogen receptor modulators offer bone protection without the side effects of estrogen replacement therapy, there are some areas of improvement for the current generation of selective estrogen receptor modulators; particularly in reducing their antagonistic properties in the central nervous system that lead to vasomotor symptoms. There are few therapies that are focused on increasing bone formation, but they offer promising avenues in which to expand the repertoire of drugs to restore bone mass. Selective androgen receptor modulators, parathyroid hormone analogs, oxytocin analogs and statins, all with improved pharmacological properties in bone, are among the potential approaches to eliciting anabolic effects in the skeleton.