Effects Of Tibolone Research Articles

Molecular analysis of human endometrium: short-term tibolone signaling differs significantly from estrogen and estrogen + progestagen signaling

Tibolone, a tissue-selective compound with a combination of estrogenic, progestagenic, and androgenic properties, is used as an alternative for estrogen or estrogen plus progesterone hormone therapy for the treatment of symptoms associated with menopause and osteoporosis. The current study compares the endometrial gene expression profiles after short-term (21 days) treatment with tibolone to the profiles after treatment with estradiol-only (E2) and E2 + medroxyprogesterone acetate (E2 + MPA) in healthy postmenopausal women undergoing hysterectomy for endometrial prolapse. The impact of E2 treatment on endometrial gene expression (799 genes) was much higher than the effect of tibolone (173 genes) or E2 + MPA treatment (174 genes). Furthermore, endometrial gene expression profiles after tibolone treatment show a weak similarity to the profiles after E2 treatment (overlap 72 genes) and even less profile similarity to E2 + MPA treatment (overlap 17 genes). Interestingly, 95 tibolone-specific genes were identified. Translation of profile similarity into biological processes and pathways showed that ER-mediated downstream processes, such as cell cycle and cell proliferation, are not affected by E2 + MPA, slightly by tibolone, but are significantly affected by E2. In conclusion, tibolone treatment results in a tibolone-specific gene expression profile in the human endometrium, which shares only limited resemblance to E2 and even less resemblance to E2 + MPA induced profiles.

Comparison of the effects of tibolone and estrogen therapy on hemostasis in surgical menopause: a randomized, double-blind, placebo-controlled study

To examine the effects of unopposed estrogen (E) and tibolone therapy on coagulation and natural anticoagulant systems in surgical menopause. A randomized, double-blind, placebo-controlled study. University hospital clinic in Turkey. Ninety healthy surgically postmenopausal women. Ninety surgically postmenopausal women were randomized into three groups: unopposed conjugated ET (0.625 mg/d, group 1), tibolone (2.5 mg/d, group 2), and identical tablets of placebo (group 3). Effects on parameters in the clotting cascade at baseline and after 24 weeks of treatment. After 6 months, fibrinogen, lipoprotein (a), and factor VIIa were decreased, and activated partial thromboplastin time was increased significantly in the ET group compared with in the placebo group. However, tibolone significantly decreased only the serum levels of factor VIIa and factor IX and prolonged the activated partial thromboplastin time, compared with placebo group. In addition, conjugated ET caused a significantly greater decrease in serum fibrinogen level than did tibolone. Neither E nor tibolone therapy led to activation of coagulation in the surgically menopausal women. Both preparations changed the overall hemostatic balance to a more fibrinolytic state.

Endometrial Effects of Tibolone

The Tibolone Histology of the Endometrium and Breast Endpoints Study is a multicenter, randomized, double-blind study designed to address the conflicting reports in the literature about the endometrial safety of tibolone (1.25 or 2.5 mg/d). Tibolone was compared with continuous combined conjugated equine estrogen (CEE) plus medroxyprogesterone acetate (MPA) (0.625 + 2.5 mg/d). Subjects were randomized in a 1:1:2 ratio to tibolone 1.25 mg/d, 2.5 mg/d, and CEE/MPA, respectively. The one-sided 95% confidence interval (CI) has been evaluated for the incidence of abnormal endometrial histology (hyperplasia or carcinoma) and hyperplasia and carcinoma separately for each of the two treatment groups and the treatment groups combined after 1 and 2 yr of treatment with tibolone, compared with CEE/MPA. A total of 3240 women were randomized, with 3224 receiving at least one dose of study medication. The incidence and upper one-sided 95% CI for the incidence of abnormal endometrium (hyperplasia or carcinoma), and hyperplasia and carcinoma separately, were calculated at end point, yr 1, and yr 2. The incidence (upper one-sided 95% CI) of abnormal endometrium at end point was 0.0 (0.5), 0.0 (0.4), and 0.2 (0.5) in the tibolone 1.25 mg, 2.5 mg, and CEE/MPA groups, respectively. During the entire treatment period, amenorrhea was reported more frequently with tibolone 1.25 mg (78.7%) and 2.5 mg (71.4%) than CEE/MPA (44.9%). The Tibolone Histology of the Endometrium and Breast Endpoints Study results confirm previous findings that tibolone does not induce endometrial hyperplasia or carcinoma in postmenopausal women, and it is associated with a better vaginal bleeding profile than CEE/MPA.

The hormone replacement therapy drug tibolone acts very similar to medroxyprogesterone acetate in an estrogen-and progesterone-responsive endometrial cancer cell line

Tibolone, a steroidogenic compound with both estrogenic and progestagenic properties, is used as an alternative for estrogen or estrogen plus progesterone hormone therapy for the treatment of symptoms associated with menopause and osteoporosis. We have evaluated whether the effect of tibolone on a human endometrial cell line is similar to, or comparable with, the effect of estradiol (E(2)), medroxyprogesterone acetate (MPA) or E(2) + MPA treatment. Using stable transfection techniques, the estrogen receptor (ER) expressing human endometrial cancer cell line, ECC1, was altered to also express both progesterone receptors (PRs). These cells were then used to assess growth regulation and expression profiling (Affymetrix U133plus2) under the influence of E(2) (1 nM), MPA (1 nM), E(2) + MPA or tibolone (100 nM). Growth assessment and comparison of profiles indicate that tibolone behaves predominantly like MPA. Furthermore, regulation of prereplication complex genes, such as the minichromosome maintenance genes, could be involved in the observed strong inhibition of growth by tibolone as well as MPA. In addition, in total, 15 genes were found to be specific for tibolone treatment. These genes were predominantly involved in regulation of the cell cycle and differentiation.

Metabolism of exogenous sex steroids and effect on brain functions with a focus on tibolone

Around the menopause, changes in ovarian secretion of steroids result in changes in brain function: hot flushes and sweating later followed by changes in mood, libido and cognition. The relationship between sex steroids and brain functions are reviewed, with focus on hormonal treatments, in particular tibolone, on the postmenopausal brain and on associations between tissue levels and brain functions. Data on steroid levels in human brain are limited. Exogenous oestrogens alone or combined with progestagens reduce hot flushes and sweating, and may favourably affect anxiety, depression and mood. Testosterone alone or combined with E 2 improves libido and mood. Tibolone reduces hot flushes and sweating, and improves mood and libido, but does not stimulate endometrium or breast, like oestrogens. Tibolone is an ideal compound for studying steroid levels and metabolism in brain in view of its structural differences from endogenous steroids and its extensive metabolism required to express its endocrine effects. Brain levels of tibolone metabolites were measured in ovariectomized cynomolgus monkeys receiving tibolone for 36 days. Compared to serum, higher levels of the oestrogenic 3α/β-hydroxytibolone and the androgenic/progestagenic Δ 4-tibolone, and lower levels of sulphated metabolites are found in various brain regions. The high levels of oestrogenic metabolites in the hypothalamus explain hot flush reduction. Combined with the presence of Δ 4-tibolone, the tibolone-induced increase in free testosterone through SHBG reduction explains androgenic effects of tibolone on mood and libido. The levels of tibolone metabolites in the monkey brain support tibolone's effects on brain functions.

Effects of tibolone on abdominal subcutaneous fat, serum leptin levels, and anthropometric indices: A 6-month, prospective, randomized, placebo-controlled, double-blind study

This study was undertaken to evaluate the effects of tibolone on abdominal subcutaneous fat, serum leptin levels (SLLs), and anthropometric indices, and to investigate potential relationships between SLLs, subcutaneous abdominal fat thickness, and anthropometric indices in postmenopausal women. In a 6-mo, prospective, randomized, double-blind, placebo-controlled study, 40 healthy postmenopausal women aged 42 to 67 y (mean: 50+/-4.7 y) were randomly assigned to 1 of 2 groups; during a 6-mo treatment period, the first group received tibolone (Livial tablet; Organon, The Netherlands; 2.5 mg/d; n=19) and the other group was given placebo (n=21). Fasting SLLs determined by enzyme-linked immunosorbent assay, subcutaneous abdominal fat thickness assessed by ultrasound, and anthropometric indices of body weight, body mass index, waist and hip circumference, and waist-to-hip ratio (WHR) were recorded at the beginning and the end of the study. Statistical analyses were performed with Mann-Whitney, Wilcoxon, and Spearman tests. P values <.05 were considered significant. No significant differences between the 2 groups were reported in terms of all baseline characteristics. After 6 mo, body weight (+0.77+/-0.43 kg) and SLLs (+14.7+/-6.4 ng/mL) increased in the placebo control group, whereas waist circumference (-2.6+/-3.0 cm), hip circumference (-3.6+/-3.5 cm), and subcutaneous abdominal fat thickness (-4.3+/-4.8 cm) decreased significantly in the tibolone group (P<.05). At the end of the study, group comparisons revealed significant differences in waist and hip circumference and subcutaneous abdominal fat thickness (P<.05). At baseline, SLLs were correlated with subcutaneous abdominal fat thickness and all anthropometric indices except WHR (P<.05). Subcutaneous abdominal fat thickness was also highly correlated with all indices except WHR (P<.0001). Tibolone was found to decrease waist and hip circumference, as well as subcutaneous abdominal fat thickness. Also, tibolone appeared to attenuate weight gain and leptin increase. SLLs and subcutaneous abdominal fat thickness were positively correlated with all anthropometric indices except WHR.

Long-term effects of tibolone on ocular functions in postmenopausal women

Hormone replacement therapy has been widely used for the prevention of postmenopausal osteoporosis and treatment of climacteric symptoms for many years, but its effect on ocular functions remains unclear. The aim of the study was to evaluate the long-term effects of tibolone on ocular functions in postmenopausal women. A total of 77 healthy women with at least 1 year of spontaneous menopause were enrolled in the study. Forty women were treated with tibolone for 6 months and 37 women were left untreated. All these patients underwent ophthalmic examination including visual acuity, intraocular pressure (IOP), tear functions, blue-on-yellow and white-on-white Humphrey visual field (HVF), visual evoked potentials (VEP) and electroretinography (ERG). There were significant differences in mean deviation of blue-on-yellow HVF, and oscillatory potentials (O1, O2, and O4) in the ERGs of the chronic tibolone users and the control (P < 0.0001, P = 0.001, P < 0.0001 and 0.05, respectively). However, no significant differences were observed in visual acuity, IOP, tear functions, white-on-white HVF and VEP. We concluded that, although tibolone had no effects on visual acuity, IOP, tear functions and VEP, it might cause some early adverse effects on the electrophysiologic and structural characteristics of the retina, which are detected by these sensitive assays. Randomized placebo-controlled studies with larger groups are needed in future research.

Long-term effects of tibolone on circulating levels of vascular cell adhesion molecules and E-selectin in postmenopausal women

Adherence of lymphocytes and monocytes to cell adhesion molecules (vascular cell adhesion molecules [VCAMs]) expressed by activated endothelial cells is the first step in the development of atherosclerotic disease. It is known that administration of tibolone for 8 weeks reduces serum levels of VCAMs in postmenopausal women. We evaluated the effects of the administration of tibolone in postmenopausal women for 1 year. Randomized, placebo-controlled, crossover trial. Healthy volunteers in an academic environment. Thirty-six healthy women in postmenopause since 1-4 years. Group A received 2.5 mg/d of tibolone and group B received placebo for 12 months; treatment was subsequently crossed over for 1 month. Serum concentrations of VCAM-1, intercellular adhesion molecule-1 (ICAM-1), and E-selectin were evaluated at baseline and at 6, 12, and 13 months. Baseline concentration of VCAM-1, ICAM-1, and E-selectin were similar in both groups. At months 6 and 12, mean concentrations of VCAM-1, ICAM-1, and E-selectin decreased significantly in group A but not in group B. At month 13, levels returned to baseline in group A, whereas they decreased significantly in group B. Tibolone causes a rapid and sustained decrease in circulating levels of VCAMs; the effect is lost soon after stopping the treatment. Tibolone induces favorable changes in endothelial function and may exert a direct cardiovascular protective effect in postmenopausal women.

Beneficial effect of tibolone on mood, cognition, well-being, and sexuality in menopausal women

Tibolone is a synthetic molecule used extensively for the management of menopausal symptoms, with the proposed additional advantage of enhanced mood and libido. Tibolone, after oral administration, is rapidly converted into 3 major metabolites: 3alpha-hydroxytibolone and 3beta-hydroxytibolone, which have estrogenic effects, and the Delta(4)-isomer, which has progestogenic and androgenic effects. The tissue-selective effects of tibolone are the result of metabolism, of enzyme regulation, and of receptor activation which vary in different tissues. Tibolone seems to be effective on estrogen-withdrawal symptoms such as hot flushes, sweating, insomnia, headache, and vaginal dryness, with results generally comparable to the effects exerted by estrogen-based treatments, and the additional property of a progestogenic activity on the endometrium. As well as relieving vasomotor symptoms, tibolone has positive effects on sexual well-being and mood, and improves dyspareunia and libido. These effects may depend on both estrogenic and androgenic actions exerted at the genital level and in the central nervous system, and on a reduction of sex-hormone-binding globulin and an increase of free testosterone, without affecting Delta-5 androgens levels. Based on the evidence available, tibolone is a valuable treatment option to relieve menopausal complaints, especially in women suffering persistent fatigue, blunted motivation, and loss of sexual desire despite an adequate estrogen replacement.

Different effects of tibolone and low-dose EPT in the management of postmenopausal women with primary headaches

The present randomized prospective study aimed to compare the effect of tibolone (T) with conventional low-dose estrogen-progestogen therapy (EPT) administered in a combined continuous regimen on the course of primary headaches in postmenopausal women requesting hormone therapy (HT) for climacteric complaints. Forty women presenting for clinical evaluation of headache (migraine without aura and episodic tension-type headache) were enrolled. The observational period lasted 7 months during which women kept a diary of the clinical characteristics of headache attacks and analgesic use. Climacteric symptoms and both anxiety and depression were also measured. After a 1-month run-in period, women received two different HT regimens: 1 mg 17beta-estradiol + 0.5 mg norethisterone acetate (EPT) or 2.5 mg T. Follow-up evaluations were planned after 3 and 6 months of treatment. Although T did not affect the number of days with migraine without aura, it significantly reduced the number of hours during which pain intensity prohibited daily activities (P < 0.001) and the number of analgesics (P < 0.001) after 3 months. Conventional low-dose EPT administered in a combined continuous regimen was confirmed to have a mild, but negative, effect on the course of migraine without aura by increasing the number of days with head pain (P < 0.001) and the number of analgesics (P < 0.001). Interestingly, both treatments were effective in the management of episodic tension-type headache, significantly reducing the number of days with head pain, severity, and analgesic consumption. In postmenopausal headache sufferers, analgesics are more effective in alleviating severe head pain when women are treated with T in comparison with low-dose EPT for climacteric complaints.

Progestagenic Effects of Tibolone are Target Gene—Specific In Human Endometrial Cells

Tibolone (Tib) exhibits progestagenic activities in addition to its tissue-specific estrogenic activities. The purpose of the current study was to determine the progestagenic actions of Tib and its metabolites using target genes known to be regulated by progestins in human endometrial glandular and stromal cells. Human endometrial glandular and stromal cells were isolated from endometrial tissue fragments and separately incubated with Tib and its metabolites. Real-time polymerase chain reaction (PCR) was used to determine the mRNA content of 17betahydroxy steroid dehydrogenase (17betaHSD, type 2) and sulfotransferase (SULT1E1) in endometrial glandular cells, and prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP1) in endometrial stromal cells. In glandular cells, Tib and Delta4-tibolone (Delta4Tib) significantly increased the content of 17betaHSD and SULT1E1 mRNA. In stromal cells, Tib and Delta4Tib increased PRL mRNA ( approximately 30% of the capacity compared to progesterone) and had little effect on IGFBP1 mRNA. Anti-progestin, RU486, reversed the induction of SULT1E1 and PRL by progesterone or Tib. Also, the two 3 hydroxyl tobolone metabolites, especially 3betaOHTib, showed some progestagenic effects. The data showed that Tib and Delta4Tib exhibited clear progestagenic effects in endometrial glandular cells by inducing 17betaHSD and SULT1E1, while in stromal cells the response was weaker in the induction of PRL and had little effect on IGFBP1. In addition, the 3betaOHTib metabolite expressed progestagenic activity. These disparate effects in two types of cells may be beneficial for maintaining endometrial cells in a quiescent state.

Semiparametric Analysis of Two‐Level Bivariate Binary Data

In medical studies, paired binary responses are often observed for each study subject over timepoints or clusters. A primary interest is to investigate how the bivariate association and marginal univariate risks are affected by repeated measurements on each subject. To achieve this we propose a very general class of semiparametric bivariate binary models. The subject-specific effects involved in the bivariate log odds ratio and the univariate logit components are assumed to follow a nonparametric Dirichlet process (DP). We propose a hybrid method to draw model-based inferences. In the framework of the proposed hybrid method, estimation of parameters is done by implementing the Monte Carlo expectation-maximization algorithm. The proposed methodology is illustrated through a study on the effectiveness of tibolone for reducing menopausal problems experienced by Indian women. A simulation study is also conducted to evaluate the efficiency of the new methodology.

Effectiveness of tibolone on the reduction of menopausal problems—a Bayesian semi‐parametric interpretation

Two major physiological problems women experience at the time of menopause are hot flush and vaginal dryness. Exploratory investigations reveal that these two binary outcomes are very much dependent as both of them have predominant oestrogenic effects. A primary interest is to investigate how the bivariate association and the marginal univariate risks are affected by repeated measurements on each woman over several months. To achieve this we propose a very general class of bivariate binary models. Parametric inference is drawn on the basis of full non-parametric Bayesian approach under Dirichlet process mixture. Study addresses some more interesting phenomena on the effectiveness of tibolone treatment in reducing menopausal problems. A simulation study further strengthens the proposed methodology.

Metabolism of tibolone and its metabolites in uterine and vaginal tissue of rat and human origin

In postmenopausal women, tibolone shows clear tissue differences in its stimulatory effects on the vagina and uterus. In rats, however, it has stimulatory effects on both tissues, with a different, more estrogenic, effect on the uterus than in humans. This may be due to differences in local metabolism. Therefore, in the present study, the metabolism of tibolone was analyzed in incubations of uterine and vaginal tissue from postmenopausal women and ovariectomized rats using radiolabeled tibolone in order to understand the tissue- and species-specific metabolism. In the rat, tibolone (50 nM) was mainly 3α-reduced to the estrogenic 3α-OH-tibolone in the uterus and vagina. The 3β-OH tibolone can be isomerized to 3α-OH-tibolone with tibolone as intermediate. In contrast, in the same tissues from postmenopausal women, the progestagenic Δ 4-isomer and estrogenic 3β-OH-tibolone were the major metabolites of tibolone. The formation of the Δ 4-isomer was higher in uterine tissue. The 3β-hydroxysteroid dehydrogenase (HSD) inhibitor epostane had no effect on tibolone metabolism in human uterine and vaginal tissue microsomes and HEK293 cells expressing the human 3β-HSD types 1 and 2 isoforms did not metabolize tibolone. Moreover, the 3β-reduction of tibolone to 3β-OH-tibolone was NADPH dependent, while the isomerization of tibolone to the Δ 4-isomer did not require a cofactor. It was therefore concluded that human 3β-HSD isoforms are not involved in the metabolism of tibolone, and that the 3β-reduction and the Δ 5–10 to Δ 4 isomerization may be catalyzed by different enzymes. In conclusion, we showed that, in hormone therapy target tissues of the rat as compared with the human, different metabolic pathways for tibolone exist and therefore result in metabolites with different pharmacological properties. The rat is therefore a poor model to predict the effects of tibolone on the uterus in postmenopausal women.

Effects of Tibolone and Continuous Combined Conjugated Equine Estrogen/Medroxyprogesterone Acetate on the Endometrium and Vaginal Bleeding: Results of the OPAL Study

The primary objective of the Osteoporosis Prevention and Arterial effects of tiboLone study was to compare the effect of tibolone and placebo on the progression of the common carotid artery intima-medial thickness; the common carotid artery intima-medial thickness and bone data will be presented elsewhere. A secondary objective was to assess the effects of tibolone (2.5 mg), continuous combined conjugated equine estrogen/medroxyprogesterone acetate [0.625/2.5 mg], and placebo on the endometrium and vaginal bleeding; these results are the subject of this report. This 3-year, three-arm, international, randomized, double-blind, parallel group, placebo-controlled clinical trial enrolled 866 postmenopausal women (aged 45-79 years). The endometrium was assessed by annual transvaginal ultrasound scans and end-of-study biopsies (United States/United Kingdom centers only). Vaginal bleeding was recorded in daily diaries. Endometrial thickness measured by transvaginal ultrasound scan increased slightly during the first year with tibolone and conjugated equine estrogen/medroxyprogesterone acetate, without any further progression. After 3 years, there were no significant differences between the tibolone, conjugated equine estrogen/medroxyprogesterone acetate, and placebo groups in the incidence of proliferation (1.4%, 4.8%, and 0%, respectively), endometrial hyperplasia (0% in all groups), or cancer (1, 0, and 1 case, respectively). During the first 3 months, bleeding/spotting rates were greater with conjugated equine estrogen/medroxyprogesterone acetate (48%) than with tibolone (18%; P < .001) or placebo (3%; P < .001). During 3 years of treatment, the incidence of bleeding/spotting was 66%, 48%, and 23% for conjugated equine estrogen/medroxyprogesterone acetate, tibolone, and placebo, respectively. The mean number of bleeding/spotting days was greater in the conjugated equine estrogen/medroxyprogesterone acetate than the tibolone or placebo groups (61, 28, and 7 days, respectively; P = .023 vs tibolone; P < .0001 vs placebo). The mean number of bleeding/spotting episodes was also greater in the conjugated equine estrogen/medroxyprogesterone acetate group (13 episodes) compared with the tibolone group (six episodes; P < .001) and placebo group (four episodes; P < .001). Vaginal bleeding was more commonly reported as an adverse event with conjugated equine estrogen/medroxyprogesterone acetate than tibolone (26.4% vs 10.8%, P < .0001) and as the reason for premature discontinuation (9% vs 2%, P = .001). Compared with conjugated equine estrogen/medroxyprogesterone acetate, tibolone has a better tolerability profile with respect to vaginal bleeding but with a similar endometrial safety. These results reinforce the endometrial safety profile of tibolone.

The effect of tibolone versus 17β-estradiol on climacteric symptoms in women with surgical menopause: A randomized, cross-over study

Objective To compare the effectiveness of tibolone and 17β-estradiol on climacteric symptoms, in a randomized, single-blind, cross-over study in surgically menopausal women. Material and methods Forty surgically menopausal women were divided randomly into two groups. Group A received treatment with tibolone for 6 months, while group B received 17β-estradiol. After 3 weeks washout period, treatment protocols were exchanged for another 6 months. The climacteric symptoms were assessed with Greene Climacteric Scale at baseline, during washout and after the treatments. Statistical analysis was done with the Wilcoxon's Sign Rank test. Results Both treatments significantly improved the scores of all subscales with respect to baseline. However, the improvement in psychological, somatic and sexual subscales were significantly superior in the tibolone group compared with 17β-estradiol group. Both treatments showed comparable improvements in the relief of vasomotor symptoms. Conclusion Our findings suggest that tibolone may improve mood, libido and somatic symptoms in surgically menopausal women to a greater extent than estrogen therapy alone.

Efecto de tibolona en el mioma uterino en pacientes tratadas con análogos de la hormona liberadora de gonadotropinas

Objectives To evaluate de effectiveness of tibolone, a synthetic steroid, as add-back therapy in patients diagnosed with leiomyoma. Tibolone has been demonstrated to be effective in inhibiting menopausal symptoms and in preventing postmenopausal bone loss. Its low estrogenic profile should not compromise the efficacy of gonadotropin-releasing hormone analogue (goserelin) in reducing the volume of uterinefibroids. Material and methods A group of 125 premenopausal women (with regular menstrual cycle) diagnosed with uterine leiomyomata suitable for surgical treatment were recruited in a randomized, prospective study that evaluated 5 treatment regimens: group 1 (control group), three doses of goserelin acetate depot (3.6 mg); group 2, 3 doses of goserelin acetate depot associated with tibolone (2.5 mg daily) from the first dose of goserelin until surgery; group 3, 3 doses of goserelin acetate depot associated with tibolone from the second dose of goserelin until surgery; group 4, 2 doses of goserelin acetate depot associated with tibolone from the second dose of goserelin until surgery, and group 5, 3 doses of goserelin acetate depot associated with conjugated equine estrogens (0.625 mg daily) from the second dose of goserelin until surgery. Modification of uterine size was evaluated with ultrasound examination and serum levels of gonadotrophins and estradiol were evaluated with the different treatment protocols. Differences were considered significant when p < 0.05. Results The mean reductions in uterine volume (%) were greater in the first 3 treatment groups (–30.1 ± 16.7; –26.4 ± 21.2; –25.1 ± 22.5; –15.6 ± 23 y –5.5 ± 15.1, respectively) and the differences were statistically significant when each group was compared with the control group (group 1). The mean concentrations of serum estradiol (pg/ml) were also significantly lower in the first 3 groups (26.2 ± 11.2; 45.7 ± 49.1; 35.9 ± 20.3; 97.9 ± 110.3; 111.4 ± 63.2, respectively). Conclusions Add-back tibolone therapy does not significantly compromise the effect of goserelin acetate in patients with uterine fibroids.

Effect of tibolone on tumor angiogenesis parameters in short-term treated women

10519 Background: Large recent studies have shown increased mammographic density, breast pain and a marginally increased risk of breast cancer in women treated with continuous combined estrogen/progestogen (ccEPT), while tibolone has a minimal effect. A placebo-controled clinical trial (STEM), approved by several ethical comities, has been initiated to assess effect and potential mechanism of action of tibolone on breast tumor. We present the results on 12 angiogenesis-related parameters. Methods: 102 women with breast cancer who had to undergo a mastectomy were treated for 2 weeks with tibolone 2.5 mg/day or placebo. RNA was extracted from tumor snap-frozen biopsies (paired before and after treatments) and reverse-transcripted into 2 cDNA batches on which 6 distinct PCRs were performed in duplicate per parameter/sample. A vascular density (VD) index was determined on CD31 specifically stained tumor sections by counting 10 fields per section on 5 distinct sections per biopsy. Results: The validity of the VD evaluation is highlighted by the high correlation coefficient (r = 0.81) between the data within the placebo group at a 2 week interval. In the tumor samples, no change of the VD index was seen. Since it could be argued that VD index could not correctly reflect a modulation of angiogenesis after only 14 days of treatment, we looked at a potential change of the expression of a large array of angiogenesis-related factors (VEGFs, VEGFRs, PAI-1). No modification of the expression in any of these factors was observed. Conclusions: Our data lead to conclude that, in this study, tibolone displays a neutral effect on angiogenesis in breast tumor. [Table: see text]

Tibolone and metabolites induce prolactin production in human endometrial stromal cells in vitro: Evidence for cell-specific metabolism

In this study, we assessed the effects of tibolone and its metabolites on the production of a progesterone sensitive parameter, prolactin, in human endometrium stroma cells in vitro. In addition, the metabolism of the compounds by isolated stromal and epithelial cells was evaluated. The reference compounds, progesterone, Org 2058, and DHT all induced prolactin production. Oestradiol also slightly induced prolactin production and enhanced the response to Org 2058. Tibolone and Δ 4-tibolone were similar with regard to potency to induce prolactin levels in the culture supernatant. Their potency was lower than that of Org 2058, similar to that of progesterone and higher than that of DHT. The efficacies of tibolone, Δ 4-tibolone and Org 2058 were similar (∼200-fold induction). The estrogenic tibolone metabolites 3α- and 3β-OH tibolone also significantly stimulated prolactin production. Their potency, however, was low since significance was reached only at the highest concentrations tested. The PR antagonist Org 31710 inhibited both tibolone- and Δ 4-tibolone-induced prolactin production. The responses of tibolone and Δ 4-tibolone were not affected by co-incubation with the androgen receptor antagonist OH-flutamide. The effect of tibolone, but not Δ 4-tibolone, was antagonized approximately 50% in combination with the highest dose (1 μM) estrogen receptor antagonist, ICI 164384. The induction of prolactin by 3α- and 3β-OH tibolone was antagonized most potently by Org 31710, but also by ICI 164384 and OH-flutamide. Tibolone is metabolized differently in epithelial and stromal cells of the human endometrium. The epithelial cells mostly produce the progestagenic/androgenic Δ 4-tibolone. The stromal cells produce predominantly the 3β-OH tibolone, and some Δ 4-tibolone, but the net effect observed with regard to prolactin production is progestagenic. When the metabolites 3α-OH, 3β-OH, and Δ 4-tibolone were added to the cultures no conversions were observed. The HPLC analyses showed no evidence for the production of sulfated metabolites. In conclusion, the net effects on endometrial stromal cells are predominantly progestagenic. Tibolone is converted by epithelial cells into Δ 4-tibolone which displays progestagenic and androgenic activities, whereas in stromal cells also the estrogenic metabolites 3α- and 3β-OH tibolone are formed.

Effects of tibolone on nuclear receptors in human endometrial cells

Tibolone regulates estrogenic activity in a tissue-selective manner. The purpose of this study was to evaluate the effects of tibolone on the mRNA content of nuclear receptors, estrogen receptor-alpha and beta (ERalpha and ERbeta), progesterone receptor (PR), and androgen receptor (AR) in human endometrial stromal and glandular cells. Human endometrial stromal and glandular cells were isolated from endometrial tissue fragments and separately incubated with tibolone and its metabolites. Nuclear receptor mRNA was determined using real-time polymerase chain reaction (PCR). In endometrial stromal cells, tibolone, Delta4-tibolone, and 3betaOH-tibolone, but not 3alphaOH-tibolone, significantly reduced ERalpha mRNA by approximately 60% and ERalpha protein by approximately 80%. No reduction of ERalpha was observed in endometrial glandular cells. Tibolone induced PR mRNAs to various extents and reached up to 6-fold in glandular cells, but only a moderate increase (approximately 1.5-fold) in stromal cells. Tibolone increased ERbeta and had little effect on AR mRNA in endometrial cells. The results showed the majority of the nuclear receptors were not significantly altered. However, tibolone significantly reduced ERalpha in stromal cells and increased PR in glandular cells. These biological effects may play essential roles in averting stimulation of the endometrium in tibolone users.