On the mechanism of action of progestins

Comparison of 7α-methyl-19-nortestosterone effectiveness alone or combined with progestins on androgen receptor mediated-transactivation

7α-methyl-19-nortestosterone (MENT) is an androgen with potent gonadotropin inhibitory activity and prostate-sparing effects. These attributes give MENT advantages over testosterone as a male contraceptive, but, as in the case of testosterone, a partial dose-dependent suppression of spermatogenesis has been observed. Combination of testosterone or MENT with synthetic progestins improves the rate of azoospermia; however, it is unknown whether these combinations affect hormone androgenicity or exert synergistic effects via progestational or androgenic interaction. Herein, using transactivation assays, we examined the ability of MENT alone or combined with several 19-nor-derived synthetic progestins to activate androgen receptor (AR)-dependent gene transcription. In addition, the capability of 7α-methyl-estradiol (7α-methyl-E2), an aromatized metabolite of MENT, to transactivate gene transcription via estrogen receptor α (ERα; ESR1) or ERβ (ESR2) was also investigated. As expected, MENT induced gene transactivation through either the progesterone receptor (PGR) or the AR. MENT was as efficient as progesterone in activating PGR-mediated reporter gene expression, but it was ten times more potent than testosterone and dihydrotestoterone in activating of AR-driven gene expression. The addition of increasing concentrations of other 19-nortestosterone derivatives (norethisterone or levonorgestrel) did not affect, in a significant manner, the ability of MENT to activate AR-dependent reporter gene transcription. The same results were obtained with different cell lines. 7α-Methyl-E2 resulted in potent estrogen activity via both ER subtypes with efficiency similar to natural E2. These results suggest that the addition of 19-nortestosterone-derived progestins, as a hormonal adjuvant in male fertility strategies for effective spermatogenic suppression, does not display any detrimental effect that would interfere with MENT androgenic transcriptional activity.

Differential regulation of endogenous pro-inflammatory cytokine genes by medroxyprogesterone acetate and norethisterone acetate in cell lines of the female genital tract

BACKGROUND

Medroxyprogesterone acetate (MPA) and norethisterone (NET) and its derivatives are widely used in female reproductive therapy, but little is known about their mechanisms of action via steroid receptors in the female genital tract. MPA used as a contraceptive has been implicated in effects on local immune function. However, the relative effects of progesterone (Prog), MPA and norethisterone acetate (NET-A) on cytokine gene expression in the female genital tract are unknown.

STUDY DESIGN

Using two epithelial cell lines generated from normal human vaginal (Vk2/E6E7) and ectocervical (Ect1/E6E7) cells as in vitro cell culture model systems for mucosal immunity of the female cervicovaginal environment, we investigated steroid receptor expression and activity as well as regulation of cytokine/chemokine genes by MPA and NET-A, as compared to the endogenous hormone Prog.

RESULTS

We show that the Prog, androgen, glucocorticoid and estrogen receptors (PR, AR, GR and ER, respectively) are expressed in both the Vk2/E6E7 and Ect1/E6E7 cell lines, and that the GR and AR are transcriptionally active. This study is the first to show ligand-, promoter- and cell-specific regulation of IL-6, IL-8 and RANTES (regulated-upon-activation, normal T cell expressed and secreted) gene expression by Prog, MPA and NET-A in these cell lines. Moreover, we show that the repression of the TNF-α-induced RANTES gene by MPA in the Ect1/E6E7 cell line is mediated by the AR.

CONCLUSION

Collectively, these data demonstrate that cell lines from different anatomical sites of the female genital tract respond differently to Prog and the synthetic progestins, most likely due to differential actions via different steroid receptors. The results highlight the importance of choice of progestins for immune function in the cervicovaginal environment. They further suggest that choice of progestins in endocrine therapy may have implications for women's risk of susceptibility to infections due to differential actions on genes involved in inflammation and immune function.

Usefulness of FSH measurements for determining menopause in long-term users of depot medroxyprogesterone acetate over 40 years of age

OBJECTIVE

To assess the usefulness of follicle-stimulating hormone (FSH) measurements for determining menopause in 40-55-year-old users of depot medroxyprogesterone acetate (DMPA).

STUDY DESIGN

FSH levels were measured in 355 blood samples from 82 amenorrheic women during an 18-month period. Blood was collected every 90 days immediately prior to DMPA administration.

RESULTS

Using FSH values>35 mIU/mL as being in the post menopausal range, 32 women (39.0%) presented at least one FSH measurement in the postmenopausal range and 14 of them (43.7%) had more than one elevated FSH measurement and were considered postmenopausal. In five users (15.6%), only the last FSH measurement was within the postmenopausal range, and in 13 women (40.6%), FSH returned to normal values following one measurement that was within the postmenopausal range.

CONCLUSIONS

The menopausal status in DMPA users in amenorrhea should be determined based on at least two consecutive high FSH evaluations, since, as shown here, 40.6% of the women with high FSH had a low FSH in the subsequent determination. FSH measurements should be done only in women>or=50 years old because there is a greater possibility of being in postmenopause. However, we do not recommend the interruption of DMPA use prior to the quantification of FSH.

Hormone-like behavioral effects of levonorgestrel and its metabolites in the male rat

Levonorgestrel (LNG), a contraceptive progestin, exhibits, besides its progestational activity, other hormone-like effects at the peripheral level. To assess whether LNG and its metabolites exert androgenic and/or estrogenic actions at the central nervous system (CNS), their effects on male sexual behavior in castrated rats were examined. LNG, 5alpha-dihydro LNG (5alphaLNG), and the 3alpha,5alpha- and 3beta,5alpha-tetrahydro derivatives of LNG (3alphaLNG and 3betaLNG, respectively) were administered for 3 weeks either alone (1000 microg/day) or in combination (300 microg/day) with 5alpha-dihydrotestosterone (DHT, 300 microg/day) or with estradiol-17beta (E(2), 5 microg/day). Copulatory behavior was assessed twice per week and sex accessory organs weights recorded at the end of treatments. LNG restored full copulatory behavior comparable to that of testosterone treated animals, although with a slight delay, whereas 5alphaLNG induced male sexual behavior in a significantly lower number of subjects. 3betaLNG and 3alphaLNG induced mounting but failed to restore intromission and ejaculation. Combined LNG+E(2) treatment fully activated mounting and intromission, but ejaculation was only partially restored. Combined 5alphaLNG+E(2) treatment and the combinations of 3alphaLNG or 3betaLNG with E(2) were significantly less effective, activating fewer intromissions and ejaculations. 3alphaLNG and 5alphaLNG, in combination with DHT, restored male sexual behavior. LNG, but not its metabolites, induced a significant increase on the weight of sex accessory organs. The overall results demonstrated that high doses of LNG induce a potent androgen agonistic behavioral effect and that its A-ring reduction diminishes this potency and enables a shift towards a weak estrogen-like effect.

Molecular interactions of levonorgestrel and its 5 alpha-reduced derivative with androgen receptors in hamster flanking organs

The 5 alpha-reduction of levonorgestrel (LNG) as well as its binding capacity to the androgen receptors of the hamster flank organ were investigated. Furthermore, the effects of LNG and its 5 alpha-reduced metabolite in the flank organ test and on [U-14C]glucose incorporation into lipids by this tissue were determined. Homogenates from female hamster flank organs were incubated in the presence of [3H]LNG at pH 7.4. The radioactive 5 alpha-LNG metabolite was isolated and its purity was assessed. Competition experiments for androgen binding receptors were carried out with 1.38 nM [3H-7 alpha-17 alpha]dimethyl-19- nortestosterone (DMNT), Kd, plus a range of increasing concentrations of the different unlabeled steroid hormones. The flank organ test was performed in vivo, and [U-14C]glucose incorporation into lipids was determined under organ culture conditions. The 5 alpha-LNG had the same binding capacity to androgen receptors (AR) as LNG in male flank organs. The flank organ test demonstrated that 5 alpha-LNG activity was similar to that observed for levonorgestrel and testosterone (T) on gonadectomized male hamster flank organs. Topical applications of LNG or 5 alpha-LNG increased [U-14C]glucose incorporation into lipids in a way similar to that of T. The overall data indicate that LNG and 5 alpha-LNG produced androgenic activity in the lipid pathway of male flank organs, and that 5 alpha-reduction is not essential for the LNG effect on this tissue.

Induction of male sexual behavior by norethisterone: role of its A-ring reduced metabolites

The estrogenic and androgenic potencies of norethisterone (NET), a synthetic nonaromatizable progestin, and three of its reduced metabolites (5 alpha-NET; 3 alpha, 5 alpha-NET; 3 beta, 5 alpha-NET) were assessed by their ability to restore male sexual behavior in castrated male rats following their chronic administration in combination with either 5 alpha-dihydrotestosterone (DHT) or estradiol (E2), or when given alone. Full restoration of mating was achieved when 3 beta, 5 alpha-NET was administered with DHT, indicating an estrogenic effect of this compound. Lower estrogenic effects were noticed with 3 alpha, 5 alpha-NET and 5 alpha-NET, while NET had very little estrogenic potency. The only effective compound to restore ejaculation, when administered with E2, was NET, indicating its androgen-like intrinsic potency. When administered alone, NET exerted the most potent effect on male behavior, followed by 5 alpha-NET, while the tetrahydro derivatives were ineffective. The observation that NET alone restored male sexual activity at a level identical to that induced by testosterone demonstrated an androgenic-estrogenic activity of this progestin exerted through its intrinsic androgenic effect, and the estrogenic effect of its tetrahydro derivatives. Overall results indicated that the metabolism of NET modulates its mode of action at the brain, and support the concept that both estrogenic and androgenic effects are required for mating activation.

Pharmacokinetics of oestrogens and progestogens

There are large inter- and intra-individual variations in the serum concentrations of natural and synthetic sex steroids irrespective of the route of administration. Oral ingestion of steroids has a stronger effect on hepatic metabolism than parenteral administration, as the local concentration in liver sinusoids are 4-5 times higher during the first liver passage. Oestradiol and oestrone are interconvertible, dependent on the local concentrations in liver and target organs, and oestrone sulphate serves as a large reservoir. The oestrone/oestradiol ratio has no physiological significance, as oestrone is only a weak oestrogen. Oestrone is both a precursor and a metabolite of oestradiol. Oestriol is extensively conjugated after oral administration. Therefore, the oestriol serum levels are similar after oral intake of 10 mg and after vaginal application of 0.5 mg oestriol resulting in similar systemic effectiveness. Conjugated oestrogens can easily enter the hepatocytes but are hormonally active only after hydrolyzation into the parent steroids. Ethinylestradiol which exerts strong effects on hepatic metabolism and inhibits metabolizing enzymes, should not be used for hormone replacement therapy. Among the progestogens, the progesterone derivatives have less effects on liver metabolism than the norethisterone derivatives (13-methyl-gonanes and 13-ethyl-gonanes). The highly potent 13-ethyl-gonanes are effective at very low doses, because of a slow inactivation and elimination rate due to the ethinyl group.

Mechanism of action of gestagens

In the mid-1950s it was shown that ovulation can be inhibited by oral administration of progesterone or of synthetic progestogens such as norethynodrel. The idea that progestogens may interfere with fertility even when administered in doses so small, that they do not invariably inhibit ovulation was launched in the mid-1960s by a group of Mexican investigators. Since then a large number of studies have been conducted on the mechanism of action of gestagens when used as contraceptives. The objective of this communication is to review the information collected so far on this topic.

Obstructive sleep apnea in premenopausal women. A comparison with men and with postmenopausal women

Because obstructive sleep apnea (OSA) is unusual in premenopausal women, we describe ten women with this syndrome and compare them to 13 postmenopausal women and with 32 men with OSA. Two premenopausal women had structural abnormalities of their pharynx, and the remaining eight were significantly more obese than men with OSA. In these eight patients, there was no relationship between pulse flow resistance and the degree of OSA in contrast to significant relationships in postmenopausal women, and men. Hypercapnia occurred in three premenopausal women, no postmenopausal women and in two men. We conclude that premenopausal women with OSA are more likely than men and postmenopausal women to have structural abnormalities of their upper airway, to be extremely obese, and to be hypercapneic, and that OSA occurs in them independent of their upper airway dimensions.

Fluctuations in quantitative features of intermediate cells in normal cervical smears during the menstrual cycle of ovulating women and contraceptive users

In this study we report on the variation in nuclear and cytoplasmic size of intermediate cells in normal cervical smears, in relationship to the week of the menstrual cycle and in relationship to the mode of contraception. A total of 18000 cells from 360 different women was studied. A significant difference in nuclear size of intermediate cells in smears from ovulating women not using contraception was found in comparison with intermediate cells in smears from women using contraceptive pills (ANOVA: F(1.312) = 4.98, p less than 0.02). Also a significant difference in the nuclear size of intermediate cells in smears from women using norgestrel- (or levonorgestrel)-containing formulas compared with lynestrenol-containing formulas was found (ANOVA: F(1.232) = 5.82, p less than 0.01). The influence of exogenous and endogenous hormones on cell populations in cervical smears is discussed. It is concluded that in studies on intermediate cells in cervical smears the contraceptive status of the women has to be taken into account.

Stereospecificity of the intracellular binding of norethisterone and its A-ring reduced metabolites

The interaction of norethisterone (NET) and four A-ring reduced metabolites of NET with cytosol receptors for progesterone (PR), androgen (AR), and estrogen (ER) was investigated. Cytosol preparations from: uteri of adult estrogen-primed castrated rats, ventral prostates of adult castrated rats and uteri of immature rats were used as the source of PR, AR, and ER respectively. 3H-Labeled ORG-2058, R-1881, and 17 beta-estradiol were used as the radioligands. The results of competitive studies disclosed that: the most efficient competitor for PR binding sites was NET (Ki = 1.1 X 10(-7) M) followed by 5 alpha-dihydro NET (5 alpha-NET), whereas the 3 alpha,5 alpha; 3 beta,5 alpha and 3 alpha,5 beta-tetrahydro NET derivatives were ineffective the most efficient competitor for AR binding sites was 5 alpha-NET (Ki = 1 X 10(-8), immediately followed by NET, while the three tetrahydro NET derivatives were not competitors and remarkable competition for ER binding sites was only exhibited by the 3 beta,5 alpha-tetrahydro NET derivative (Ki = 4.6 X 10(-8) M) and to a lesser extent by its 3 alpha,5 alpha-epimeric alcohol, while NET and 5 alpha-NET were completely ineffective. These findings demonstrate the stereospecificity of the intracellular binding of NET and its reduced metabolites with cytosol steroid putative receptors, and provide biochemical support to the understanding of the variety of hormone-like effects observed after the in vivo administration of NET.

Pharmacokinetic and pharmacodynamic basis for the treatment of metastatic breast cancer with high-dose medroxyprogesterone acetate

Postmenopausal patients with metastatic breast cancer were treated with medroxyprogesterone acetate (MPA) (Clinovir) in dosages between 500 and 1500 mg orally per day. The relation of MPA plasma concentrations and endocrine effects were studied in a longitudinal fashion. MPA exerted suppressive effects on the basal and gonadotropin-releasing hormone (GnRH) stimulated gonadotropin secretion, cortisol, dehydroepiandrosterone (DHEA), and estradiol (E2) in a dose-dependent manner leading to a complete suppression with 1500 mg orally per day. The depression of thyroid hormones (T3 and T4) coincided with a depression of the thyroxine-binding index (TBI). MPA did not affect human growth hormone (hGH), basal and thyrotropin-releasing hormone (TRH) stimulated thyroid-stimulating hormone (TSH) and aldosterone. Basal and TRH-stimulated prolactin (PRL) secretion showed a slight but distinct elevation. From these data it is concluded that in postmenopausal patients MPA exerts its antitumor activity by an interference with the hypothalamo-pituitary adrenal axis in the sense of a selective pharmacologic hypophysectomy leading to complete suppression of adrenal steroid secretion. Additionally, MPA inhibits tumor cell growth through the progesterone receptor. A dual mechanism for the antitumor activity of high dose is postulated MPA: ablative through suppression of the hypothalamo-pituitary-adrenal axis and subsequent estrogen deprivation, and additive via the progesterone receptor directly on the tumor cell. The significance of gonadotropin suppression in the postmenopause for breast cancer growth is unclear. The depression of T3 and T4 is due to a depression of thyroid hormone-binding proteins. The elevation of PRL secretion may be explained by a slight estrogenic activity of MPA metabolites.

Effects of synthetic steroid contraceptives on biliary lipid composition of normal Mexican women

The effects of two hormonal contraceptives upon the biliary lipid composition of Mexican women were evaluated in a prospective study. Twenty-one healthy volunteers of reproductive age were allocated into three groups (7 subjects each). Group I served as the experimental control (all subjects were bearing a non-medicated IUD), group II received i.m. norethisterone enanthate (NET-e) 200 mg every two months, and group III received an oral combination of 1-norgestrel 150 micrograms and ethinyl estradiol 30 micrograms. The bile lithogenic index as assessed by the relative proportion of cholesterol to bile acids and lecithin was determined in duodenal bile samples obtained before (baseline), during (4 months), and after (12 months) contraceptive administration. The results indicated that NET-e administration resulted in a slight although significant increase of the lithogenic index while the oral formulation did not. The overall data were interpreted as demonstrating that administration of these steroid contraceptives does not constitute a risk factor in terms of gallstone formation in the population studied. The estrogen-like behavior exhibited by NET-e is discussed.