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Tibolone, Transdermal Estradiol or Oral Estrogen-Progestin Therapies: Effects on Circulating Allopregnanolone, Cortisol and Dehydroepiandrosterone Levels

Posted on: Friday, 27 May 2005, 03:00 CDT

Abstract

The aim of the present study was to evaluate, in healthy postmenopausal women, the impact of tibolone (2.5 mg), transdermal estradiol (50 g) (TE) and different oral estrogen-progestin regimens, conjugated equine estrogens (0.625 mg) plus medroxyprogesterone acetate (5 mg) (CEE + MPA) and estradiol (2 mg) plus norethisterone acetate (1 mg) (E2 + NETA) on circulating estradiol, progesterone, allopregnanolone, cortisol and dehydroepiandrosterone (DHEA) levels. Blood samples were collected before and after 1, 3, 6 and 9 months of treatment in 85 postmenopausal women. Estradiol levels increased (p < 0.001) in the TE, CEE + MPA and E2 + NETA groups after 1 month of therapy, but did not change in the tibolone group during the entire follow-up period. Both E2 + NETA and tibolone treatments induced an increase in progesterone levels (p < 0.05) after 1 year of therapy. Allopregnanolone levels showed an increase in all estrogen-based groups, being significant after 3 months of treatment (p < 0.01). Patients receiving tibolone showed a significant increase in allopregnanolone levels at 3 months (p < 0.05), but lower than in the other groups. Cortisol levels decreased significantly in the TE and CEE + MPA groups after 6 months and 12 months of treatment, respectively. Neither tibolone nor E2 + NETA treatments modified circulating cortisol levels. DHEA levels significantly (p < 0.05) decreased after 6 months of TE or estrogen-progestin therapies independently of the presence or the type of progestin used. In contrast, DHEA remained stable throughout the 12 months of treatment with tibolone. The increase of allopregnanolone, a steroid with sedative and anxiolytic properties, in response to these different treatments could underlie, at least in part, the central effects that hormone replacement therapy and tibolone have on anxiety, mood and behavior. Unlike estrogen-based therapy, tibolone treatment did not reduce the DHEA milieu in the menopause, and thus did not enhance the androgen deficiency syndrome in postmenopausal women.

Keywords: Tibolone, hormone replacement therapy, allopregnanolone, DHEA, cortisol

Introduction

The menopausal transition is characterized by several endocrine, neuroendocrine and metabolic modifications that severely affect many biological functions, inducing a wide spectrum of symptoms throughout the postmenopausal period. Although much attention has been given to menopausal hypoestrogenism and the options in hormone replacement therapy (HRT) (i.e., estrogens and progestins), relatively less attention has been paid to the age-related changes in adrenal function and the impact of hormone treatment on adrenal steroidogenenis. Whether the vasomotor instability, mood changes, anxiety, depression and sleep disturbances are specific symptoms of the hypoestrogenism-induced changes in the postmenopausal neuroendocrine pathways, the middle age in women is also characterized by the andrenopause, which enhances the co-called androgen deficiency syndrome. Low libido, persistent and inexplicable fatigue, blunted motivation and a general reduced sense of well-being are all symptoms referable to reduced levels of circulating androgens [1]. In particular, it has been demonstrated that adrenocortical secretion of the Δ5-androgen dehydroepiandrosterone (DHEA) and its sulfate (DHEAS) decline with age, while cortisol levels remain unchanged [2]. This decline in Δ5-androgens, the main peripheral precursors of estrogens and androgens in the postmenopause, and the parallel increase in the cortisol/DHEAS ratio, have been reported to be in part responsible for several physiological and/orphysiopathological age-related changes [3]. Epidemiological data suggest a link between the decrease of DHEA levels and the declines in cognition and immune function, and the increases in insulin resistance and neoplasia incidence [4]. Conversely, the administration of DHEA improved physical and psychological well-being and cognitive performances in aged subjects [4].

In addition to the decline of circulating DHEA levels, the postmenopausal period is also characterized by a decrease in allopregnanolone serum levels. Allopregnanolone is a 3&945; reduced metabolite of progesterone, and the adrenal cortex represents the main source of synthesis/release of this steroid in the postmenopause [5]. Allopregnanolone shows potent endogenous anxiolytic properties and modulates cerebral function, affecting mood and cognitive performances, thus supporting the hypothesis that the modification of allopregnanolone levels might be involved in the mood changes and cognitive impairment observed in the postmenopausal period [6]. Moreover, progesterone metabolites, acting on membrane (GABA^sub A^) receptors, regulate the expression of myelin proteins, stimulate myelin synthesis and reduce the aging-associated morphological abnormalities of myelin in the peripheral nervous system (PNS) as well as the central nervous system (CNS) [7].

Previous studies have hypothesized a direct effect of estrogen- based therapies on adrenal function [8,9] and more recent data have shown that transdermal estradiol (TE) and other transdermal and oral estrogen-progestin regimens induced an increase of circulating allopregnanolone levels, but a decrease in DHEA serum levels in postmenopausal women [10].

Both allopregnanolone and DHEA have been defined as neuroactive steroids, starting from the evidence that they modulate cerebral function, affecting mood and cognitive performances, thus supporting the hypothesis that modification in neurosteroidogenesis might be responsible for several related disturbances induced by the postmenopausal condition. Therefore, the observation that estrogen and estrogen-progestin therapies modulate the levels of these steroids indicates that the impact of HRT on neurosteroidogenesis might contribute to the role played by HRT on central symptoms.

Tibolone is a synthetic steroid with estrogenic, androgenic and progestagenic properties, largely used for the treatment of climacteric symptoms, being particularly efficacious on CNS-linked symptoms. Tibolone is rapidly metabolized after administration into 3a-hydroxytibolone and 3β-hydroxytibolone, which solely bind the estrogen receptor (ER), and into a Δ4-isomer with affinity for the progesterone receptor (PR) and androgen receptor (AR), but not the ER. The concentrations of tibolone metabolites and the metabolic regulation of hormonal activities vary in relation to the tissue type [11]. Clinical data have shown that tibolone plays a beneficial effect in the reduction of hot flushes and sweating, and an improvement of mood, insomnia and libido in postmenopausal women [12]. Since no data are available on the effects of tibolone on adrenal function and in particular on neuroactive steroid levels, we aimed to investigate its effects in comparison to other HRT regimens.

Therefore, we evaluated allopregnanolone, DHEA and cortisol serum levels after 1, 3, 6, 9 and 12 months of therapy with tibolone, TE and various oral HRT regimens in postmenopausal women in order to investigate the effects of tibolone on age-related changes in adrenal function.

Material and methods

Patients

A total of 85 postmenopausal women with a mean age of 53.7 2.6 years, a mean body mass index (BMI) of 23.2 1.5 kg/m^sup 2^ and a mean postmenopausal age of 5.3 2.7 years, were enrolled after they had provided written informed consent (Table I). Inclusion criteria were: 3 years or more of postmenopausal age; no history of chronic diseases and/or use of chronic medications; no hormonal treatments; no history of familial cancer diseases; and no psychiatric diseases. None of the subjects suffered from endocrine disease, and none was being treated with psychoactive or anti-inflammatory drugs. The patients were subdivided into the following five groups on the basis of the HRT adopted:

1. Group TE: 40 women (hysterectomized and ovariectomized) and treated with transdermal estradiol (TE) (Dermestril 50, Rottapharm).

2. Group E2 + NETA: 18 women treated with continuous combined estradiol plus norethisterone acetate (E2 + NETA) (Kliogest, Novo Nordisk: E2 2 mg + NETA 1 mg (28 cps)).

3. Group CEE + MPA: 10 women treated with continuous combined conjugated equine estrogens plus medroxyprogesterone acetate (CEE + MPA) (Premelle C, Wyeth Lederle: CEE 0.625 mg + MPA 5 mg (28 cps)).

4. Group Tibolone: 17 women treated with tibolone (Livial, Orgnanon; tibolone 2.5 mg (30 cps)).

Blood samples were collected between 08.00 and 09.00 before and after 1, 3, 6, 9 and 12 months of HRT. Estradiol, progesterone, cortisol, DHEa and allopregnanolone were assessed on all blood samples, The local ethical committee approved the protocol.

Estradiol, progesterone, cortisol and DHEA assays

Serum concentrations of estradiol, progesterone, cortisol and DHEA were measured by specific commercially available radioimmunoassay (RIA) kits (Radim, Pomezia, Rome, Italy). The sensitivity of the assay for E2 was 10 pg/ml, and the intra- and interassay coefficients of variation were 2.1% and 4.4%, respectively. The sensitivity of the assay for progesterone was 50 pg/tube and the intra- and interassay coefficients of variation were 6.5% and 8.7%, respectively. The s\ensitivity of the assay for Cortisol was 0.9 g/l, and the intra- and interassay coefficients of variation were 3.6% and 6.2%, respectively. The sensitivity of the assay for DHEA was 0.2 ng/ml, and the intra- and inter-assay coefficients of variation were 3.8% and 6.9%, respectively.

Allopregnanolone assay

Allopregnanolone evaluation was performed after ether extraction and Chromatographie partition on Sep-Pak C18 cartridges using a specific previously described RIA method [5]. The sensitivity of the assay was 10 pg/tube and the intra- and interassay coefficients of variation were 7.2% and 9.1%, respectively.

Statistical analysis

Data are shown as mean standard deviation and as simple percentages. One- and two-way analysis of variance (ANOVA) was used to compare hormonal levels and their percentage change during follow- up among the four groups of patients. Bonferroni's multiple comparison test was used to compare the hormonal levels at all follow-up times among the different HRT groups. Bonferroni's multiple comparison test for two-factor interactions was used to compare the percentage change in hormonal levels among the ten groups. Alpha value for the Bonferroni test was set at 0.05. Statistical analysis was performed with NCSS 2001 software (Number Cruncher Statistical Systems, Kaysville, UT, USA).

Table I. Percentage changes of estradiol, progesterone, allopregnanolone, cortisol and dehydroepiandrosterone (DHEA) levels after 6 months and 12 months of treatment with different estrogen plus progcstin therapies and tibolone in comparison to pre-therapy levels. All data are mean values standard deviation.

Results

Estradiol

E2 levels showed a progressive increase during follow-up in the patients treated with TE, E2 + NETA and CEE + MPA, being already highly significant after 1 month (p < 0.001). The E2 levels remained high during the entire treatment period, with no difference among the three groups. In contrast, there were no increases in E2 levels during the whole therapy in the group of patients treated with tibolone (Figure 1). The percentage increases of estradiol after 1 year of therapy with TE, E2 + NETA and CEE+ MPA were 306.5 30.8%, 289.3 30.2% and 171.4 16.5%, respectively (Table I).

Figure 1. Estradiol levels during different estrogen plus progcstin therapies and tibolone. All data are mean values standard deviation. + p < 0.001 vs. pretherapy.

Progesterone

Progesterone levels significantly increased during follow-up in the tibolene-treated group with a rapid and marked increase at 1 month (p < 0.05). The percentage increase, after 1 year treatment with tibolone, was 50.0 4.7% (Table I). The patients treated with CEE + MPA showed a significant (p < 0.05) increase in progesterone levels starting from the third month of therapy; the percentage increase, after 1 year of therapy, was 48.4 4.2%. In contrast, in the patients receiving E2 + NETA and TE, progesterone levels remained unchanged during the 1-year follow-up (Figure 2).

Allopregnanolone

Allopregnanolone levels showed a rapid and marked increase in all estrogen-based groups, being significant after 3 months of treatment (p < 0.01). Patients receiving tibolone showed a significant increase in allopregnanolone levels at 3 months (p < 0.05), but lower than the other groups (Figure 3). The percentage increase after 1 year treatment with tibolone was 44.9 4.0%. For TE, E2 + NETA and CEE + MPA the values were 106.9 9.2%, 103.1 8.1% and 132.4 12.8%, respectively (Table I).

Cortisol

Cortisol levels showed a progressive decline at 6 months in the TE group (p < 0.05), reaching the minimum at the end of 1 year of therapy (p < 0.01). In the patients treated with CEE + MPA, cortisol levels became significantly lower at the end of follow-up (p < 0.05). The percentage decrease of cortisol levels, after 1 year of treatment with TE and CEE + MPA, was 20.6 1.8% and 17.5 1.4%, respectively (Table I). No significant changes were observed for cortisol levels in the tibolone and E2 + NETA groups (Figure 4).

Figure 2. Progesterone levels during different estrogen plus progestin therapies and tibolone. All data are mean values standard deviation. * p < 0.05 vs. pretherapy.

Figure 3. Allopregnanolone levels during different estrogen plus progestin therapies and tibolone. All data are mean values standard deviation. * p < 0.05 vs. pretherapy; p < 0.01 vs. pretherapy. + p < 0.001 vs. pretherapy.

Figure 4. Cortisol levels during different estrogen plus progestin therapies and tibolone. All data are mean values standard deviation. *p < 0.05 vs. pretherapy; p < 0.01 vs. pretherapy, +p < 0.001 vs. pretherapy.

Dehydroepiandrosterone

DHEA levels showed a progressive decline throughout the treatment in the TE, E2 + NETA and CEE + MPA groups reaching statistical significance from 6 months of follow-up (p < 0.01). Tibolone treatment was not associated with any changes in circulating DHEA levels (Figure 5). The percentage decrease of DHEA levels, after 1 year of treatment with TE, E2 + NETA and CEE + MPA, was 36.9 9.1%, 414 9.0% and 41.1 8.6%, respectively.

Figure 5. Dehydroepiandrosterone levels during different estrogen plus progestin therapies and tibolone. All data are mean values standard deviation. p < 0.01 vs. pretherapy.

Discussion

This study has demonstrated that women who received estrogen- based therapies showed a significant increase in the peripheral levels of allopregnanolone from the third month of treatment. Indeed, data of the TE, E2 + NETA and CEE + MPA regimens confirm previous experimental and clinical results, showing a positive modulation exerted by estrogens on adrenal synthesis/release of allopregnanolone [7,13]. The mechanism by which estradiol modulates the level of allopregnanolone is still unclear. Estrogens may act directly, in a tissuespecific manner, on 5α-reductase and on 3α-hydroxysteroid dehydrogenase (3αHSD), the enzymatic pathways involved in allopregnanolone synthesis from progesterone [14-16].

Our data demonstrate also that tibolone increased allopregnanolone levels but less than other HRT formulations after 12 months of treatment, probably owing to the weaker estrogenic profile of tibolone on the enzymatic pathways involved in 3α, 5α-THP syntheses. Indeed in vitro transactivation studies have shown that only the hydroxylated metabolites of tibolone displayed a relevant agonistic activity for Erα, but this is approximately 30 times lower than the relative agonistic effect of estradiol [17]. Moreover, the Erβ relative agonistic activities were at least 10-fold lower for 3α- and 3β-hydroxytibolone [18].

Moreover, serum levels of allopregnanolone could be related, at least in part, to the increased level of progesterone observed during the treatment with CEE + MPA and with tibolone. It has been demonstrated that progesterone intramuscular injection results in a time- and dose-dependent increase in circulating allopregnanolone levels [19]. In contrast, the E2 + NETA regimen did not determine any significant modification in progesterone plasma level. This different profile shown by CEE + MPA and E2 + NETA regimens in the modulation of progesterone levels could be related to the chemical structure of NETA and MPA that are, respectively, not metabolised and partially metabolised into progesterone. On the other hand, the mechanism by which tibolone can increase progesterone synthesis or release is less clear, but, certainly, this result appears to be remarkable.

In conclusion, these results allow us to speculate that positive mood changes described after HRT as well as after tibolone administration might be dependent also on the increased levels of allopregnanolone, a neurosteroid with sedative and anxiolytic properties.

Furthermore, this study has described the effects of HRT and tibolone on DHEA plasma levels, with contrasting results in relation to the different treatments. TE, E2 + NETA and CEE+ MPA regimens induced a concomitant and similar decrease of DHEA concentrations, thus suggesting that the addition of progestin molecules to the estrogenalone therapy does not induce further modifications of DHEA level. In addition, no differences in decreasing DHEA levels have been reported using different progestins. All these results suggest that estrogens and not progestins are able to influence DHEA synthesis/release, confirming previous data reporting a decrease in DHEA levels during HRT [10]. Our observations provide additional evidence that HRT exacerbates the androgen deficiency condition, which is typical in postmenopausal women, probably blunting adrenal activity (as suggested by the concomitant reduced levels of cortisol and DHEA) and increasing sex hormone binding globulin (SHBG) during oral therapies [9]. Our data suggest that TE, CEE+ MPA and E2 + NETA may modify the enzymatic pattern of the adrenal gland, enhancing the conversion of progesterone to allopregnanolone and reducing the activity of the other biosynthetic pathways that lead to cortisol or DHEA production.

In contrast, 12 months of treatment with tibolone did not modify circulating cortisol levels. This is in agreement with previous results showing that tibolone administration did not induce any changes in basal cortisol level and in the cortisol response to adrenocorticotropic hormone (ACTH) stimuli [20,21]. Furthermore, these data indicate that tibolone treatment did not influence serum DHEA concentration during 1 year of therapy. Some experimental studies have shown an increase in the androgen milieu in women treated with tibolone [22,23] but, to date, the mechanism by which this synthetic steroid modulates DHEA secretion is still unknown; further trials are needed to delineate the molecular aspects of the tissuespecific action of tibolone on adrenal steroidogenesis and its interaction with ACTH stimult on DHEA release.

Unlike estrogen-based therapy, tib\olone does not affect the androgen milieu in postmenopausal women, and does not aggravate the physiological androgen deficiency syndrome. These observations led us to speculate that the increase in well-being, libido, sexual pleasure and arousal, observed in postmenopausal women treated with tibolone, depend not only on the direct effect of its active metabolites in specific brain areas, but also, probably, from the lack of reduction of endogenous DHEA synthesis/release and from the lack of increase of SHBG levels as is induced by oral estrogen therapy [9,22].

In conclusion, tibolone shows reduced estrogenic effects on adrenal allopregnanolone and cortisol synthesis/release in comparison to TE and other oral estrogen-progestin therapies and does not affect the androgenic milieu in postmenopausal women. This characteristic can be used individually to select the most appropriate treatment to counteract the physical and psychological symptoms of each postmenopausal woman.

Acknowledgment

This reseach was partially supported by a grant from the Foundation Cassa di Risparmio A. Miniato.

References

1. Braunstein GD. Androgcn insufficiency in women: summary of critical issues. Fertil Steril 2002;77:S94-S99.

2. Liu CH, Laughlin GA, Fischer UG, Yen SSC. Marked attenuation of ultradian and circadian rhythms of dehydroepiandrosterone in postmenopausal women: evidence for a reduced 17,20 desmolase enzymatic activity. J Clin Endrocrinol Metab 1990;71:900-906.

3. Mortola JF, Yen SSC. The effects of oral dehydroepiandrosterone on endocrine-metabolic parameters in postmenopausal women. J Clin Endocrinol Metab 1990;71:696-704.

4. Baulieu EE. Dehydroepiandrosterone: a fountain of youth? J CHn Endocrinol Metab 1996;81:3147-3151.

5. Genazzani AR, Petraglia F, Bernardi F, et al. Circulating levels of allopregnanolone in humans: gender, age and endo-crine influences. J Clin Endocrinol Metab 1998;83:2099-2103.

6. Mellon SH. Neurosteroids: action and clinical relevance. J CHn Endocrinol Metab 1994;78:1003-1008.

7. Melcangi RC, Azcoitia I, Ballabio M, et al. Neuroactive steroids influence peripheral myelination: a promising opportunity for preventing or treating age-dependent dysfunctions of peripheral nerves. Prog Ncurobiol 2003;71:57-66.

8. Kraemer RR, Synovitz LB, Gimpel T, Kracmer GR, Johnson LG, Castracane VD. Effect of estrogen on serum DHEA in younger and older women and the relationship of DHEA to adiposity and gender. Metabolism 2001;50:488-493.

9. Casson PR, Elkind-Hirsch KE, Buster JE, Hornsby PJ, Carson SA, Snabes MC. Effect of postmenopausal estrogen replacement on circulating androgens. Obstet Gynecol 1997;90:995-998.

10. Bernardi F, Pieri M, Stomati M, et al. Effect of different hormonal replacement therapies on circulating allogpregnanolone and dehydroepiandrosterone levels in postmenopausal women. Gynecol Endrocrinol 2003;17:65-77.

11. Moore R. Livial: a review of clinical studies. Br J Obstet Gynaecol 2001;106(Suppl 19):1-21.

12. Genazzani AR, Petraglia F, Facchinetti F. Effects of Org OD 14 on pituitary and peripheral beta-endorphin in castrated rats and postmenopausal women. Maturitas 1987;S1:35-48.

13. Genazzani AR, Bernardi F, Stomati M, et al. Effects of estradiol and raloxifene analog on brain, adrenal and serum allopregnanolone content in fertile and ovariectomized female rats. Neuroendocrinology 2000;72:162-170.

14. Yokoi H, Tsuruo Y, Miyamoto T, Ishimura K. Steroid 5 alpha- reductase type 1 immunolocalized in the adrenal gland of normal, gonadectomized, and sex hormone-supplemented rats. Histochem Cell Biol 1998;109:127-134.

15. Penning TM. 3 Alpha-hydroxysteroid dehydrogcnase: three dimensional structure and gene regulation. J Endocrinol 1996;150:S175-S187.

16. Cheng YJ, Karavolas HJ. Conversion of progesterone to 5α- pregnane-3,20-dione and 3&945;-pregnan-20-one by rat medial basal hypothalamus and the effects of estradiol and stage of estrus cycle on the conversion. Endocrinology 1993;93:1157-1162.

17. de Gooyer ME, Kleyn GT, Smits KC, Edervecn AG, Verheul HA, Kloosterboer HJ. Tibolone: a compound with tissue specific inhibitory effects on sulfatase. MoI Cell Endrocrinol 2001;183:55- 62.

18. de Gooyer ME, Deckers GH, Schoonen WG, Verheul HA, Kloosterboer HJ. Receptor profiling and endocrine interactions of tibolone. Steroids 2003;68:21-30.

19. de Wit H, Scmitt L, Purdy R, Hauger R. Effects of acute progesterone administration in healthy menopausal women and normally- cycling women. Psychoneuroendocrinology 2001;26:697-710.

20. Abdalla HI, Hart DM, Lindsay R, Beastall GH. Organon OD 14 (tibolone) and menopausal dynamic hormone profiles. Maturitas 1986;8:81-85.

21. Kicovic PM, Cortes-Prieto J. Luisi M, Milojevic S, Franci F. Placebo-controlled cross-over study of effects of Org OD 14 in menopausal women. Reproduction 1982;6:81-91.

22. Doren M, Rubig A, Coelingh Bennink HJ, Holzgreve W. Differential effects on the androgen status of postmenopausal women treated with tibolone and continuous combined estradiol and norethindron acetate replacement therapy. Fertil Steril 2001;75:554- 559.

23. Erel CT, Elter K, Akman C, et al. Mammographic changes in women receiving tibolone therapy. Fertil Steril 1998;69:870-875.

N. PLUCHINO1, A.D. GENAZZANI2, F. BERNARDI1, E. CASAROSA1, M. PIERI1, M. PALUMBO3, G. PICCIARELLI1, M. GABBANINI1, M. LUISI1, & A.R. GENAZZANI1

1 Division of Obstetrics and Gynecology, University of Pisa, Italy, 2 Division of Obstetrics and Gynecology, University of Modena, Italy, and 3 Division of Obstetrics and Gynecology, University of Catania, Italy

Correspondence: A.R. Genazzani, Department of Obstetrics and Gynecology, University of Pisa, Via Roma 35, 56100 Pisa, Italy. Tel: + 39-50-592603. Fax: + 39-50-553410. E-mail: a.genazzani@obgyn.med.unipi.it

Copyright CRC Press Mar 2005

Source: Gynecological Endocrinology

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