Tibolone and its effects on bone: a review

Effect of Tibolone on Bone Mineral Density in Postmenopausal Women: Systematic Review and Meta-Analysis

Low bone mineral density (BMD) on postmenopausal women causes bone fragility and fracture risk. Tibolone seems to prevent bone loss. Therefore, this systematic review with meta-analysis synthesizes the tibolone effect on BMD percent change in lumbar spine (LS), femoral neck (FN), and total hip (TH) in postmenopausal women. Controlled trials that provided tibolone evidence on the efficacy of tibolone in preventing loss of BMD were included. Regarding the included studies, a pooled mean difference (MD) with 95% confidence intervals (95%CI) was estimated to determine the BMD percentage change. Eleven studies were identified and eight were included in the quantitative analysis. Tibolone at a dose of 2.5 mg increased BMD compared with non-active controls at 24 months in LS (MD 4.87%, 95%CI: 4.16-5.57, and MD 7.35%, 95%CI: 2.68-12.01); and FN (MD 4.85%, 95%CI: 1.55-8.15, and 4.21%, 95%CI: 2.99-5.42), with Hologic and Lunar scanners, respectively. No difference was observed when tibolone 2.5 mg dose was compared with estrogen therapy (ET) at 24 months, LS (MD -0.58%, 95%CI: -3.77-2.60), FN (MD -0.29%, 95%CI: -1.37-0.79), and TH (MD -0.12%, 95%CI: -2.28-2.53). Therefore, tibolone increases BMD in LS and FN compared to non-active controls, and there was no showed difference with ET.

A Review of Analytical Methods for the Determination of Tibolone: Pharmacokinetics and Pharmaceutical Formulations Analysis and Application in Doping Control

Background:

Tibolone is a synthetic steroid commercialized by Organon under the brand name Livial (Org OD14), which is used in hormone therapy for menopause management and treatment of postmenopausal osteoporosis. Tibolone is defined as a selective tissue estrogenic activity regulator (STEAR) demonstrating tissue-specific effects on several organs such as brain, breast, urogenital tract, endometrium, bone and cardiovascular system.

Aims:

This work aims to (1) present an overview of important published literature on existing methods for the analysis of tibolone and/or its metabolites in pharmaceutical formulations and biological fluids and (2) to conduct a critical comparison of the analytical methods used in doping control, pharmacokinetics and pharmaceutical formulations analysis of tibolone and its metabolites.

Results and conclusions:

The major analytical method described for the analysis of tibolone in pharmaceutical formulations is High Pressure Liquid Chromatography (HPLC) coupled with ultraviolet (UV) detection, while Liquid Chromatography (LC) or Gas Chromatography (GC) used in combination with Mass Spectrometry (MS) or tandem mass spectrometry (MS/MS) is employed for the analysis of tibolone and/or its metabolites in biological fluids.

Neuroactive steroids, neurosteroidogenesis and sex

The nervous system is a target and a source of steroids. Neuroactive steroids are steroids that target neurons and glial cells. They include hormonal steroids originated in the peripheral glands, steroids locally synthesized by the neurons and glial cells (neurosteroids) and synthetic steroids, some of them used in clinical practice. Here we review the mechanisms of synthesis, metabolism and action of neuroactive steroids, including the role of epigenetic modifications and the mitochondria in their sex specific actions. We examine sex differences in neuroactive steroid levels under physiological conditions and their role in the establishment of sex dimorphic structures in the nervous system and sex differences in its function. In addition, particular attention is paid to neuroactive steroids under pathological conditions, analyzing how pathology alters their levels and their role as neuroprotective factors, considering the influence of sex in both cases.

Endocrinology of menopause

Menopause is a natural process that occurs in women's lives as part of normal aging. Many women go through the menopausal transition with few or no symptoms, while some have significant, or even disabling, symptoms. This manuscript reviews the physiologic processes and symptoms connected with menopause and the diseases associated with menopause, as well as how menopausal symptoms are managed.

Effects of administering testosterone undecanoate in rats subjected to physical exercise: effects on the estrous cycle, motor behavior and morphology of the liver and kidney

The aim of the work was evaluate the effects of testosterone undecanoate (TU) treatment combined with moderate physical training on: the estrous cycle, body weight (BW), motor behavior (MB), and the morphohistology of the reproductive system, the liver and kidney in rats. Female Wistar rats (180 g - 250 g) were divided as follows: sedentary + TU (S + TU), trained + TU (T + TU), sedentary + vehicle (S + V), trained + vehicle (T + V). The rats swam 50 min/Day, strapped with a 5% BW load, for 4 weeks. During this training, (BW) was monitored daily as well as the estrous cycle (EC) by vaginal smear. The TU (15 mg/kg s.c) was administered 3 times/week for 4 weeks. At the end of the study, data on MB, BW and morphohistopathological changes in viscera were compiled. The (T + TU) group had on average, a higher (BW) in the fourth week compared to the first week, and (BW) higher than (S + V) and (S + TU) groups. We noted an interruption in the EC and a decrease in weight of ovaries in animals treated with TU. In addition, there was an increase in the relative weight of the heart in groups (T + V) and (T+ TU), and kidneys in group (T + TU). Histopathological analysis showed periportal congestion and isolated foci of hepatic necrosis in rats with TU. Thus, TU combined with training abolished the EC, promoted ovarian atrophy, liver necrosis, cardiac hypertrophy and a decrease in motor activity.

Biological options to enhance periprosthetic bone mass

There is a potential for the use of pharmacological agents to enhance the quality of bone around a total hip or knee prosthesis, reducing the risk of implant failure or periprosthetic fracture. Bisphosphonates are currently used for the management of postmenopausal osteoporosis and recent investigations also suggest a potential role for the management of postoperative periprosthetic bone loss. Current evidence suggests that the short-term gains may not be sustained in the long term. Teriparatide and parathyroid hormone 1-84 have been licensed to treat postmenopausal osteoporosis and may also be investigated for the potential to enhance periprosthetic bone mass. In addition, other agents such as calcitonin and strontium ranelate, non-anabolic agents such as doxycycline, and recombinant OPG adeno-associated virus (rAAV) gene therapy, may in the future provide solutions for enhancing periprosthetic bone mass.

Serum leptin levels and body composition in postmenopausal women treated with tibolone and raloxifene

OBJECTIVE

To compare body composition and serum leptin levels in untreated postmenopausal women and postmenopausal women treated with tibolone or raloxifene.

DESIGN

This was a prospective, randomized, controlled study. Sixty-eight postmenopausal women were randomized to receive either no treatment (group A, n = 21) or tibolone 2.5 mg/day (group B; n = 23) or raloxifene 60 mg/day (group C; n = 24). All women underwent height, weight, body mass index evaluation and dual energy x-ray absorptiometry determination of body composition at the beginning of the study and after 12 months. Serum leptin levels were determined at the beginning of the study and after 1, 3, 6, and 12 months in all groups.

RESULTS

Women in group A showed no significant changes in both fat and lean mass of arms and legs, whereas a significant increase in trunk fat mass, total fat mass, total percentage of body fat, and trunk percentage of fat was detected 1 year after the beginning of the study. After 12 months, the total percentage of fat mass was significantly higher in group A compared with group B, and the trunk percentage of fat mass was significantly higher in group A compared with groups. In subjects in groups B and C, after 1 year, fat mass, both total and at all areas evaluated, did not show any significant change compared with baseline values. In subjects in group B, total lean and lean mass of the trunk and legs increased significantly at the end of the study, whereas no significant changes were observed in lean mass, total and at all areas evaluated in subjects in group C. After 12 months, total lean mass and lean mass of the legs were significantly higher in group B compared with the other groups. In group A, serum leptin levels were significantly increased at the end of the study compared with baseline values. Leptin concentrations were significantly higher in group A compared with groups B and C after 6 and 12 months. No significant change in serum leptin levels in subjects in groups B and C was detected throughout the study. Serum leptin levels showed a positive, significant correlation with all body composition parameters and body mass index in all groups at the beginning and at the end of the study.

CONCLUSIONS

The present study confirms that postmenopausal hypoestrogenism leads to increased fat content and serum leptin levels. Raloxifene and tibolone seem to prevent postmenopausal body composition changes without significant modifications of serum leptin levels.

Where are we with postmenopausal hormone therapy in 2005?

Recently, two large randomized placebo-controlled studies on long-term postmenopausal hormone replacement therapy, the Heart and Estrogen/progestin Replacement Study (HERS) and the Women's Health Initiative (WHI), have raise a lot of controversies, especially on the cardiovascular aspects. We briefly review these two trials and discuss what we know and do not know about postmenopausal hormone therapy, including the evidence on novel choices such as raloxifene and tibolone.

Long-term effects of tibolone on mammographic density

OBJECTIVE

To investigate the long-term effect of tibolone on mammographic density.

DESIGN

Open-label, nonrandomized study.

SETTING

Academic research environment.

PATIENT(S)

Postmenopausal women.

INTERVENTION(S)

Tibolone was administered orally, mammograms were performed annually.

MAIN OUTCOME MEASURE(S)

Mammographic density according to the Wolfe classification, performed by two independent radiologists, both of whom were blinded to treatment group.

RESULT(S)

No statistically significant differences were found between the two groups in baseline demographic data. There were no statistically significant differences in mammographic density between the control and active groups at baseline or at 10 years.

CONCLUSION(S)

This pilot study shows that tibolone does not adversely alter the mammographic density of the breasts over 10 years of treatment.

Breast cancer and post-menopausal hormone therapy

From the introduction of post-menopausal hormone replacement therapy (HRT) there has been great concern that HRT could possibly increase the risk of breast cancer. Prolonged exposure to endogenous oestrogens undeniably increases the risk of breast cancer. Questions that are important and until now only partly answered, are the following. Are oestrogens tumour promoters, as they induce mitosis, lead to proliferation and, therefore, accelerated growth of clinically occult pre-existing tumours? In addition to this, are they genotoxic mutagenic carcinogens, or could they initiate tumours by way of accumulation of incessant DNA-replication damage mechanism? Opinions vary as to the effect of the addition of a progestogen. There is a multitude of different progestogens which could bind with differing affinity to progesterone receptor PR-A or PR-B, and which have different physiological functions via differential gene regulation. The action of a progestogen on the oestrogen-induced cellular mitotic activity could be synergistic or antagonistic (by different pathways: oestrogen receptor downregulation, activating of metabolic pathways within the breast or stimulation of apoptosis)? Over 60 observational studies and two randomized trials provide evidence that the small but significant increase in risk appears with long-term current post-menopausal hormone use. The addition of a progestogen does not decrease the risk as seen with oestrogens alone and might increase the risk further. It is not clear whether there is a difference in risk with sequentially combined versus continuously combined HRT. Many questions nevertheless still remain. Is the risk increase limited to lean women only? What about risk-modifying factors such as alcohol use and a positive family history for breast cancer? Are tumours detected under HRT less aggressive, is there a better prognosis and is the mortality not increased while morbidity is? And is HRT contraindicated for women with a positive family history for breast cancer or in those women who have been treated for breast cancer? And finally, are there alternative options for these women?

Estrogenic effects of 7alpha-methyl-17alpha-ethynylestradiol: a newly discovered tibolone metabolite

Tibolone is a synthetic steroid that is prescribed to postmenopausal women for relief of climacteric symptoms and prevention of osteoporosis. It has been reported to be metabolized in a tissue-selective manner to three steroids that collectively have weak estrogenic, progestogenic, and androgenic activities. Recently, a new tibolone metabolite, 7alpha-methyl-17alpha-ethynyl-17beta-estradiol (7alpha-Me-EE2), was identified in women. In this report, we describe the pre-clinical estrogenic activities of this metabolite and compare these effects to those obtained with 17alpha-ethynyl-17beta-estradiol (EE2) and 17beta-estradiol (E2). In an in vitro ligand-binding assay, 7alpha-Me-EE2 bound to both human estrogen receptor (ER)-alpha and -beta with IC(50)'s of 1.2 and 3.0 nM, respectively. Using MCF-7 human breast cancer cells that express high levels of ER-alpha, 7alpha-Me-EE2 transactivated an estrogen response element (ERE)-tk-luciferase reporter gene construct with an EC(50) of 0.021 nM. Likewise, 7alpha-Me-EE2 stimulated MCF-7 breast cancer cell proliferation with an EC(50) of 0.002 nM. In immature female rats, subcutaneous (s.c.) administration of 7alpha-Me-EE2 stimulated uterine wet weight gain with an ED(50) of 0.2 microg/kg. Moreover, 7alpha-Me-EE2 induced uterine complement component C3 gene expression, an estrogenic marker of epithelial cell stimulation, with an ED(50) of 0.5 microg/kg. When compared to EE2 and E2, 7alpha-Me-EE2 exhibited equivalent or greater potencies and efficacies in these assays. In summary, these results indicate that 7alpha-Me-EE2 is a very potent estrogen. This steroid appears to be the most potent estrogenic metabolite of tibolone identified to date, and additional studies are, therefore, warranted regarding the role of this metabolite in the biological actions of the drug.

Androgen effects on bone and muscle

Bone health and strength are dependent on the coupling of cone resorption and bone formation. This process is governed by the interaction of osteoclasts and osteoblasts plus the modulating influence of the bone mechanicosensory cells-the osteocytes. Both sex steroids-estrogen (E) and testosterone (T)- have receptors on all bone cells, with androgen dominance on osteoblasts and osteocytes. Specific receptors for the weaker androgens, such as DHEA have also been identified. The activity of the sex steroids, influenced by various enzymes found in bone, is reflective of the hormone ligand before its binding to the bone cells. As a result, T acts both directly and via its aromatization to estradiol. The activity of the androgens also varies with the bone surface; periosteal cells, for example, do not have 5alpha-reductase activity, indicating that T is the active metabolite at this clinically important site. Androgens influence bone cell function via local and systemic growth factors and cytokines. By enhancing osteoblast differentiation, androgens regulate bone matrix production, organization, and mineralization. Androgens also regulate osteoclast recruitment and activity. Endogenous androgens increase bone mineral density (BMD) in both adolescent and adult premenopausal women. Women with excess endogenous androgen-for example, those with hirsutism and polycystic ovary syndrome (PCOS)-have increased BMD compared with normal young women. E and androgen therapy increases BMD to a greater degree than does E therapy alone. This is true for both oral combinations of esterified E and methyltestosterone and for subcutaneous T implants. Androgenic progestins have an additive effect on BMD when combined with E therapy and have the further advantage of being protective to the endometrium in E-treated women. Androgens increase muscle mass and strength. The resulting improvement in physical activity leads to the activation of bone-forming sites and the stimulation of the bone formation-modulating cells, the osteocytes. Mechanical loading, when combined with hormone therapy, results in greater osteogenic response than does either alone.