Effect of orally administered oestrogens on circulating oestrogen profiles in post-menopausal women

Does dietary exposure to 17α-ethinylestradiol alter biomarkers related with endocrine disruption and oxidative stress in the adult triploid of Danio rerio?

This study was conducted to investigate a comprehensive effect of 17α-ethinylestradiol (EE2) in zebrafish (Danio rerio) with the emphasis on endocrine disruption, oxidative stress and detoxification processes at different levels. Adult male triploid zebrafish were exposed to EE2 administered in feed at two concentrations - 10 and 1000 μg/kg for six weeks. The estrogenic potential of EE2 was evaluated using an analysis of vitellogenin, gene expression focused on reproductive disorders and gonad histological examination. The alterations in antioxidant and detoxification status were assessed using analyses of enzyme activities and changes in transcriptional levels of selected genes. The most significant changes were observed especially in fish exposed to a high concentration of EE2 (i.e., 1000 μg/kg). Such high concentration caused extensive mortality (25 %) mainly in the second half of the experiment followed by a highly significant decrease in the length and body weight. Similarly, highly significant induction of vitellogenin level and vtg1 mRNA expression (about 43,000-fold compared to the control) as well as a significant downregulation of gonad aromatase expression (cyp19a1a) and histological changes in testicular tissue were confirmed in this group. In the group exposed to environmentally relevant concentration of EE2 (i.e., 10 μg/kg), no significant differences in vitellogenin were observed, although all fish were positive in the detection of vitellogenin compared to control, where only 40 % of individuals were positive. In addition, the high concentration of EE2 resulted in significant alterations in most monitored antioxidant and detoxifying enzymes with the exception of catalase, followed by strongly significant upregulation in mRNA expression of gsr, gpx1a, cat and cyp1a genes. Furthermore, a significant decrease in the glutathione reductase activity was recorded in fish exposed to 10 μg EE2/kg. To our knowledge, this is the first study which reports the effects of subchronic per oral exposure to EE2 in adult triploid zebrafish.

Oestrogen status in relation to the early training responses in human thumb adductor muscles

AIMS

The aims of this study were to identify the mechanisms for the early response to training in women of different oestrogen status and to determine whether any oestrogen and exercise effects on these would be additive.

METHODS

We monitored training (ten 5-s contractions per day for 12 weeks)-induced changes in the size, strength, voluntary activation capacity and index of crossbridge force state (i.e. rapid stretch to isometric torque ratio), in the thumb adductor muscles of postmenopausal [eight who had never used, and 14 who were using, hormone replacement therapy (HRT)] and seven premenopausal eumenorrhoeic women. The contralateral untrained muscle was used as a control.

RESULTS

There was a significant effect of oestrogen status on the magnitude of training-induced strength increment, with the non-HRT postmenopausal group exhibiting the greatest benefits (28 +/- 6%, P = 0.024) from training. There were no significant or commensurate changes in either cross-sectional area or voluntary activation capacity. The index of crossbridge force state improved most in the no-HRT group (19 +/- 7%, P < 0.05).

CONCLUSIONS

Presence, rather than absence of oestrogen, is associated with relatively higher muscle function which limits the potential for any further training-induced increments in muscle performance, as would be expected if the muscle strengthening actions of training and oestrogen share a common, partially saturable physiological pathway. The mechanism that is involved in the early training-induced strength increment in the three differing oestrogen groups cannot be due to increased size or recruitment. It would appear instead that increased motor unit firing frequency is involved.

Metabolism of endogenous and exogenous reproductive hormones

Estradiol and progesterone are produced in abundance by the ovary of the reproductive-age female (and by the placenta in pregnancy). Serum levels of both hormones are very low in the postmenopause, and indistinguishable from women who have undergone castration. Postmenopausal women have higher levels of aromatase in skin and adipose and convert androstenedione to estrone more effectively than younger women. Estradiol is well absorbed orally, but undergoes extensive first-pass effect resulting in production of the less potent metabolites estrone and estrone sulfate. Ethinyl estradiol is well absorbed, potent, and has more pronounced effects in the production of important hepatic proteins. Progesterone is absorbed orally only if ingested in a micronized form, has a relatively short serum half-life, and is metabolized to products with little biologic activity. The synthetic progestogens are abundant in number; potent in effect; and well absorbed orally, vaginally, and transdermally. New formulations of estrogens and progestogens and new delivery systems promise to provide gynecologists and patients with a long list of potential solutions to contraceptive needs and alternatives for hormone replacement therapies.

Bioavailability of norethisterone acetate alone and in combination with estradiol administered in single or multiple oral doses to postmenopausal women

OBJECTIVES

Twenty-four postmenopausal women were randomly allocated to a cross-over trial for an investigation of the pharmacokinetics of norethisterone acetate (NETA; 0.5 mg), administered alone or in combination with estradiol (E2; 1 mg), both after a single oral dose. In a second trial, the above combination of 0.5 mg NETA with 1 mg E2 was administered daily for 28 days.

METHODS

Plasma levels of NET, E2, estrone (E1) and estrone sulphate fraction containing an admixture of estrone glucuronide (E1S/E1G) were measured by radioimmunoassay at various intervals up to 72 h in the first trial and at the same intervals after the 28th day in the second trial.

RESULTS

In the first, single-dose trial, pharmacokinetic parameters of NET were similar for NETA administered alone and its combination with E2. There was no statistically significant difference in the area under curve values AUC0-24 and AUC0-infinity and no apparent major differences were observed for other pharmacokinetic parameters. No carry-over effects due to the cross-over design were seen. The multiple dosage in the second trial did not cause any major changes in the pharmacokinetic parameters of NET, except for the AUC0-24 and AUC0-infinity values which were significantly higher than those seen in the first trial. The levels of E2 exhibited, shortly after the intake of E2, a rapid burst. The levels gradually decreased to a nadir followed by an increase to the main peak and by the subsequent elimination phase. The difference between the peak and nadir levels was significant (P < 0.05) in the second, multiple-dose trial. This bimodal pattern was not observed in earlier studies. The main metabolite of E2 was E1S/E1G, followed by E1, as could be seen from the AUC0-infinity values. These were, in both trials, approximately 300 and 7-times higher for the E1S/E1G and E1, respectively, than those for E2. For all analytes, the AUC0-24 values were significantly higher in the second trial than those found in the first trial, indicating accumulation upon repeated administration. Pharmacokinetics of all analytes remained linear in the second trial, as follows from the statistically established equality of AUC0-24 found in the second, multiple-dose trial with AUC0-infinity in the first, single-dose trial. The absorption half-life and t-max values of E1S/E1G appeared to be considerably shorter than those of E1 in both trials.

CONCLUSIONS

The bioavailability of NET was not influenced by its combination with 1 mg E2. The most abundant metabolite of E2 was the E1S/E1G fraction, which may have served as the main source of E2 and other estrogens due to metabolic interconversions during the absorption and elimination phases.

Effect of conjugated estrogen on peripheral flow-mediated vasodilation in postmenopausal women

Estrogen replacement protects against cardiovascular morbidity and mortality in postmenopausal women. Conjugated estrogen is the main hormone used in these studies. However, the vascular effects of this type of estrogen are, to a large extent, unexplored. The objective of this study was to evaluate short-term endothelium-dependent vascular effects of intravenously conjugated estrogen at 2 dose levels. Eleven postmenopausal women were included. Each study subject was given 2.5 and 5 mg of conjugated estrogen or placebo in random order with at least 1 week between each investigation in a double-blind study design. The vascular reactivity of the brachial artery was studied using the duplex technique before and 30 minutes after the intravenous administration of study drug. Reactive hyperemia was used to study the flow-mediated vasodilation. Serum estradiol increased significantly and dose dependently 5 minutes after conjugated estrogen infusion. The flow-mediated vasodilation at baseline before drug administration was 1.8 +/- 2.0% (mean +/- SD) after an average 400% increase in local blood flow. Conjugated estrogen at a dose of 2.5 mg caused an increase in flow-mediated vasodilation from 1.8 +/- 2.1% at baseline to 5.4 +/- 2.8% after infusion (p <0.05 vs placebo), whereas 5 mg caused an increase from 1.9 +/- 1.5% at baseline to 7.0 +/- 3.3% after infusion (p <0.05 vs placebo). Intravenous injection of conjugated estrogen significantly improves the peripheral vascular reactivity in postmenopausal women.

Long-term effects of hormone replacement therapy on symptoms of angina pectoris, quality of life and compliance in women with coronary artery disease

OBJECTIVE

The aim of the present study was to evaluate the effects of HRT on symptoms of angina pectoris, quality of life and factors of importance for compliance in women with ischemic heart disease.

METHODS

Sixty postmenopausal women with coronary artery disease were randomized into three groups: one group received transdermal 17 beta-estradiol at a dose of 50 micrograms per 24 h alone for 18 days followed by 10 days of combined treatment with medroxyprogesterone acetate (MPA) 5 mg orally; the second group received placebo and the third group received conjugated estrogens orally for 18 days followed by a combined treatment with MPA for 10 days. Clinical evaluations were performed at baseline, after 3, 6 and 12 months. The investigations included gynecological history. occurrence of climacteric symptoms, quality of life evaluation, cardiac history and symptoms of angina pectoris.

RESULTS

Forty-six women (77%) completed the study during 1 year. The following cardiac events occurred in the women who completed the study: one patient was hospitalized because of congestive heart failure (patch), two patients because of angina pectoris, one patient because of coronary bypass operation (CEE) and three patients underwent balloon dilatation (placebo), all three on CEE. Among the 14 women who discontinued, two patients had TIA (patch), one experienced palpitations (CEE) and one woman died from myocardial infarction (placebo). Overall improvement in mood and cognitive functions were reported in all three treatment groups.

CONCLUSIONS

HRT does not seem to have negative effects on symptoms of angina pectoris and seems to increase quality of life in older women with coronary heart disease. It also seems safe from the cardiovascular point of view.

Bioavailability of orally administered sex steroids used in oral contraception and hormone replacement therapy

The concept of bioavailability is discussed with particular references to the sex steroids. Problems encountered in the measurement of bioavailability of these steroids and the various factors that may affect their bioavailability are briefly described. Information regarding the bioavailability of the estrogens and gestogens, some of which are prodrugs, used in oral contraception and hormone replacement therapy is summarized and the implications regarding the clinical use of these steroids are discussed.

Formation of ethinylestradiol in postmenopausal women during continuous treatment with a combination of estradiol, estriol and norethisterone acetate

Previous studies indicated that during treatment of postmenopausal women with preparations containing norethisterone, a small proportion of the progestogen is aromatized into ethinylestradiol. We therefore investigated the serum concentrations of estradiol, ethinylestradiol and norethisterone in 25 patients of a gynecological practice who were continuously treated for climacteric complaints with a combination of 2 mg estradiol, 1 mg estriol and 1 mg norethisterone acetate for a time period between 4 months and 6 years. Blood sampling occurred between 1 and 20 h after intake of the last tablet. The mean serum concentration of estradiol was 138 +/- 50 (53-279) pg/ml, of ethinylestradiol 18.1 +/- 13.5 (0-44) pg/ml, and of norethisterone 5.1 +/- 3.5 (0.7-11.6) ng/ml. The serum concentrations of estradiol showed a broad maximum between 1 and 14 h, and those of norethisterone a steep rise to maximum within 1-4 h after intake followed by a subsequent decline. Contrary to this, the ethinylestradiol levels were not related to the time after application indicating that the aromatization of norethisterone mainly occurs in peripheral tissue. There was no correlation between age, body mass index or duration of treatment and the ethinylestradiol levels. It is concluded that in the presence of the high estradiol concentrations the low conversion rate of norethisterone into ethinylestradiol is probably without clinical significance.

Profiles of plasma estrogens, progesterone and their metabolites after oral or vaginal administration of estradiol or progesterone

Doses of 100 mg of micronized progesterone (P) and of 0.5 mg of micronized estradiol (E2) were administered vaginally and orally, respectively, in the early follicular phase of the menstrual cycle in six premenopausal women. In the second cycle, the same doses were administered in the same subjects, orally for P and vaginally for E2. Serial blood samples were collected and the following steroids were assayed by highly reliable techniques: P, E2, estrone (E1), deoxycorticosterone (DOC), 5 alpha- and 5 beta-pregnanolone and the sulfates of E1, E2, and DOC. Circulating P and E2 levels were higher after vaginal than after oral administration, while those of E1 were similar after either route. Metabolites of P (DOC, DOCS and pregnanolone) were higher after oral administration. Concerning estrogen sulfates, E1S concentrations were similar whichever the route, while those of E2S were lower after oral than after vaginal administration. This study has confirmed that metabolism of ingested P and E2 occurs mainly in the intestine. Moreover, P was predominantly metabolized to 5 alpha-reduced derivatives, whatever the route of administration. In view of the metabolic pathways which are operative and of the peripheral plasma levels which were found, the vaginal route appears to be more adequate than the oral one for hormone replacement therapy.

Short-term effects of smoking on the pharmacokinetic profiles of micronized estradiol in postmenopausal women

Because smoking is associated with an increased risk of osteoporosis, yet a decreased risk of endometrial carcinoma, a state of relative hypoestrogenism induced by smoking has been suggested. However, because previous data are unclear and do not reflect current trends in smoking intensity and estrogen prescriptions, we examined the estrogen profiles of postmenopausal women, by smoking status, both before and after oral micronized estradiol. Baseline levels of estrone, estradiol, estrone sulfate, and estrone glucuronide were similar in nonsmokers and smokers, but unbound (non-sex-hormone-binding-globulin--bound) estradiol was significantly lower in smoking women (p less than 0.05) and sex-hormone-binding-globulin--binding capacity was higher (p less than 0.001). After 1 or 2 mg of micronized estradiol, estrone and estradiol serum profiles were similar but unbound estradiol was significantly lower in women who were smokers (p less than 0.05). Serum estrone glucuronide rose with treatment but was indistinguishable in nonsmokers and smokers. However, maximum changes in serum estrone sulfate were greater in smokers after administration of estrogen, suggesting a hepatic effect. Urinary estrone glucuronide levels increased after 8 hours of oral estrogen but were similar in nonsmokers and smokers with the two doses. It appears that even moderate smoking, as studied here, induces significant changes in hepatic estrogen metabolism and is best reflected by alterations in serum estrone sulfate and sex-hormone-binding-globulin--binding capacity that result in decreased serum unbound estradiol. However, these changes do not appear to require increasing the estrogen dosage to achieve physiologic levels of estrogen in postmenopausal smokers.

Pharmacokinetics and biotransformation of orally administered oestrone sulphate and oestradiol valerate in post-menopausal women

The pharmacokinetic properties and biotransformation of two orally active oestrogens, piperazine oestrone sulphate (PE1S, 2.5 mg/day) and oestradiol valerate (E2V, 2.0 mg/day), given alone or in combination with levonorgestrel (LNG, 250 micrograms/day) were compared in 8 post-menopausal women, using a randomized cross-over design. The end points measured in peripheral plasma included oestrone (E1), oestradiol (E2), oestriol (E3), oestrone sulphate (E1S), oestradiol sulphate (E2S) and oestriol sulphate (E3S). In addition, LNG and sex-hormone-binding globulin SHBG concentrations were also assessed. The plasma levels of E3 were invariably below the detection limit (220 pmol/l). The levels of all the other oestrogens analyzed were consistently higher and the area under the curve significantly greater (except in the case of E3S) following PE1S administration than those recorded after E2V ingestion. The terminal half-lives of the circulating oestrogens measured after PE1S administration did not differ from those found after E2V administration. After 21 days of PE1S administration (in combination with LNG for the last 10 days), the maximum levels of all the oestrogens (except those of E2) were significantly higher than those seen after the first dose. No such difference was observed after E2V administration. There was no difference between the effects of the two treatment regimens with regard to the E1/E2 ratios, but the E1/E1S ratios were significantly lower after PE1S treatment than after E2V administration. It is concluded that, compared with an equivalent dose of PE1S, daily repeated oral administration of E2V yields consistently lower peripheral plasma levels of E2 and its principal metabolites. However, in contrast to PE1S therapy, prolonged administration of E2V does not result in an accumulation of the circulating oestrogens measured.

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.