Animal toxicity studies performed for risk assessment of the once-a-month injectable contraceptive Mesigyna

Estradiol dominance induces hemodilution and mild hematological alterations in mifepristone-treated rats

We examined that an estradiol-dominant state against progesterone could affect hematological parameters through hemodilution because estradiol is known to increase plasma volume via oncotic pressure. We performed a 2- and 3-week repeated oral dose study with mifepristone, a progesterone receptor antagonist, in female rats and examined erythrocyte counts, hemoglobin, hematocrit, plasma volume, levels of estradiol and progesterone, water intake, and water loss. Mifepristone treatment decreased some hematological parameters mildly and increased plasma volume. There were no remarkable changes in the balance of water intake and water loss through urination. Both estradiol and progesterone levels and the ratio of estradiol to progesterone increased. Therefore, our findings indicate that repeated mifepristone treatment increases estradiol levels and plasma volume, resulting in lower erythrocyte counts, hemoglobin, and hematocrit. The present study proved the possible contribution of estradiol to understanding the toxicological significance of mifepristone-induced hemodilution.

Long-term progestin-only contraception in humans versus animal models

Abnormal uterine bleeding is the leading indication for discontinuation of long-term progestin-only contraceptives. Histological sections of endometria from long-term progestin-treated patients display abnormally enlarged blood vessels that are prone to bleed in a nonuniform manner. Because it has been complex to attain patients willing to complete long-term studies, and good quality endometrial tissues have proven difficult to obtain, animal models have been used to obviate this problem. In this review, we describe these models including the guinea pig, an animal model we have previously investigated, to assess the mechanisms involved in abnormal uterine bleeding following long-term progestin-only contraception.

Risk of breast cancer during hormone replacement therapy: mechanisms

Regarding estrogen replacement therapy, two main mechanisms have to be considered for it to be discussed as a potential carcinogen in the breast, and also considering the World Health Organization definition of estrogens and estrogen/progestogen combinations as “carcinogenic”: (i) the proliferative/apoptotic effects on already pre-existing estrogen-sensitive cancer cells and (ii) the production of possible genotoxic estrogen metabolites. By addition of the progestogen component, as is usual in non-hysterectomized women, both mechanisms can lead to an increased risk compared to estrogenonly therapy. The detailed mechanisms underlying the development of the benign breast epithelial cell into clinically relevant breast cancer cells are very complicated. Based on these mechanisms, the following simplified summary of the main steps explains that: (i) an increased risk cannot be excluded, (ii) especially when estrogens are combined with progestogens, but (iii) there are differences between the preparations used in therapy; (iv) the risk seems to be very rare, needing very special cellular and extracellular conditions, (v) and could even be decreased in special situations of estrogen therapy. It is concluded that when critically reviewed, an increased risk of breast cancer during hormone replacement therapy cannot be excluded in very rare cases. Definitive mechanistic evidence for a possible causal relationship with carcinogenesis still remains open.

Long-term effects of GnRH agonist, GnRH antagonist, and estrogen plus progesterone treatment on apoptosis related genes in rat ovary

OBJECTIVE

To define the long-term effects of GnRH antagonist, GnRH agonist, and estrogen plus progesterone treatments on apoptosis and apoptosis-related gene expressions, including bcl2, bax, and cyt c in rat ovary.

DESIGN

Prospective placebo-controlled experimental study.

SETTING

Obstetrics and Gynecology and Medical Biology and Genetics university departments.

ANIMAL(S)

Forty female wistar rats that were 3 to 4 months of age.

INTERVENTION(S)

Forty rats were randomly divided into 4 groups of 10 each. In group 1 (control) each rat received normal saline as placebo by gastric lavage. In group 2 (GnRH agonist) 1 mg/kg leuprolide acetate in depot form was given for 30 days. In group 3 (GnRH antagonist) each animal received 0.1 mg/kg cetrorelix every 2 days. In group 4 (estrogen plus progesterone) 0.5 mg/kg estradiol valerate and norethisterone enantate in depot form was given every 30 days. After 60 days, the animals were killed.

MAIN OUTCOME MEASURE(S)

Assessment of morphology, histology of ovaries, determination of the number of apoptotic cells, and analysis of apoptosis-related gene expression of bcl2, bax, and cyt c in the rat ovaries.

RESULT(S)

Long-term GnRH antagonist treatment significantly increased bax gene expression, but the ratio of bcl2:bax gene expression was constant compared with control group. The GnRH agonist treatment significantly increased cyt c gene expression, and estrogen plus progesterone treatment significantly decreased bcl 2 and significantly increased cyt c expressions. In the estrogen plus progesterone group, ovaries were cystic and larger than in the other groups. There was no significant morphologic change between the other groups.

CONCLUSION(S)

Long-term administration of GnRH agonist, GnRH antagonist, and estrogen plus progesterone can modulate the apoptosis-related genes in rat ovary. Although GnRH antagonist treatment does not influence apoptosis, GnRH antagonist and estrogen plus progesterone treatments seem to influence apoptosis in rat the ovary. Further clinical studies focusing on the effect of these agents on apoptosis-related genes could be performed.

The World Health Organization defines hormone replacement therapy as carcinogenic: is this plausible?

In June 2005 the World Health Organization's International Agency for Research on Cancer (IARC) classified combined hormone contraception and menopausal therapy as carcinogenic in humans. The IARC's function is to identify potential carcinogens associated with nutrition, environment and pharmaceutical products. They do not produce risk-benefit analyses for any country or population. Their conclusions are highly controversial in that no proof is presented for a causal relationship of estrogens with reproductive cancer, be it plausibility according to mechanisms of action or experimental evidence in an animal model. Equating natural compounds like estradiol with defined carcinogens like asbestos, tobacco smoke as well as indispensable drugs such as aspirin and tamoxifen is of no substantial clinical relevance. Thus, there are no new reasons to change current management principles with combination hormone contraception and therapy.

IARC monographs program on carcinogenicity of combined hormonal contraceptives and menopausal therapy

The World Health Organization International Agency for Research and Cancer (IARC), in June 2005, has classified combination hormone contraception and menopausal therapy as carcinogenic in humans. The IARC's distinction is to identify potential carcinogens associated with nutrition, environment and pharmaceutical products. They do not produce risk-benefit analyses for any country or population. Their conclusions are highly controversial in that no proof is presented for a causal relation of estrogens with reproductive cancer, be it plausibility according to mechanisms of action or experimental evidence in the animal model. Equating natural compounds like estradiol with defined carcinogens like asbestos, tobacco smoke as well as indispensable drugs such as aspirin and tamoxifen is of no substantial clinical relevance. Thus, there are no new reasons to change current management principles with combination hormone contraception and therapy.

Systemic and histopathologic changes in Beagle dogs after chronic daily oral administration of synthetic (ethinyl estradiol) or natural (estradiol) estrogens, with special reference to the kidney and thyroid

ABSTRACT Four groups of 3 male and 3 female sexually mature Beagle dogs were treated daily po with either ethinyl estradiol (EE) or estradiol (E2). A fifth group of 4 males and 4 females acted as a control group. Three groups of dogs were treated with EE: One group was treated at dose levels of 2.0, 1.5, and 1.0 mg/kg for 6 mo; the other 2 groups received either 0.5 mg/kg or 1.0 mg/kg for 1 yr. The fourth group was treated with 5.0 mg/kg E2 for 1 yr. Results obtained for the clinical, hematological, and biochemical parameters and the histopathologic findings of most organs and tissues in EE- and E2-treated dogs were essentially comparable to those documented in the literature for dogs treated with synthetic or natural estrogens. Chronic treatment with EE or E2 induced similar effects, with the exception of mesothelial proliferation of the genital serosa, which was observed in EE-treated dogs only. Additional new estrogen-related findings were observed in the kidneys and thyroid glands of EE- and E2-treated dogs. Increased interstitial fibrous tissue occurred at the corticomedullary junction and in the outer cortex of the kidney. It appeared to originate primarily from the perivascular fibrous tissue of branches of the renal arteries and veins. Extension of this lesion into the renal parenchyma resulted in secondary atrophic changes of tubules and glomeruli. The treatment relationship and specific characteristics of this renal alteration differentiated it from other chronic renal interstitial and vascular diseases. Squamous metaplasia of urogenital tract epithelia, including renal cortical tubule epithelium, occurred as expected in both EE- and E2-treated dogs. Unexpectedly, squamous metaplasia of thyroid follicular epithelium also occurred. It was present in scattered follicles of both EE- and E2-treated dogs. The renal and thyroid changes did not alter clinicopathological function tests for either of these organs. These 2 new findings extend the list of estrogen-related effects in the dog.

New once-a-month injectable contraceptives, with particular reference to Cyclofem/Cyclo-Provera

Once-a-month injectable contraceptives containing a progestogen and an estrogen have been developed that disrupt vaginal bleeding patterns less than the widely used progestogen-only preparations. Pharmacokinetic studies were undertaken of dosages and ratios of the progestogens and the respective estrogens. In Phase III clinical trials, annual pregnancy rates were below 0.4% for Mesigyna (norethisterone enanthate/estradiol valerate, Schering AG, Berlin, Germany) and below 0.2% for Cyclofem (MPA/E2C) (medroxyprogesterone acetate/estradiol cypionate, Aplicaciones Farmaceuticas, SA, Mexico and PT Tunggal, Indonesia). More than two-thirds of women had predictable, regular cycles, and discontinuation due to bleeding-related problems occurred less than half as often as with progestogen-only injectables. With MPA/E2C, return to fertility is similar to that observed with other hormonal or intrauterine methods, and both products have little effect on lipids or hemostasis. Introductory trials of MPA/E2C in 12000 women with 100000 woman-months of experience confirmed the high efficacy of the product in routine use. The use of MPA/E2C in a non-reusable injection device, Uniject (Becton Dickinson, Franklin Lakes, NJ) is discussed. Once-a-month hormonal contraceptives have been shown to provide a safe contraceptive option for all women and an alternative for women who wish to use injectable formulations that cause less disruption in vaginal bleeding and minimal side effects.

Use of norethisterone and estradiol in mini doses as a contraceptive in the male. Efficacy studies in the adult male bonnet monkey (Macaca radiata)

Administration of norethisterone (NET) or NET + estradiol benzoate using an Alzet minipump or as once-a-month intramuscular injection of their depot forms, NET-enanthate (NET-EN) and estradiol valerate (E-val), resulted in azoospermia in all monkeys (n = 13) within 60 to 150 days of treatment. Although addition of depot form of testosterone (T, 20 mg/month) to the regimen restored the behavioral response typical of a normal male, it did not reverse the azoospermic state. Serum T (heightened nocturnal) levels were significantly reduced (> 85%, p < 0.001) in all the treated groups. Evidence for blockade in spermatogenesis following treatment was obtained by DNA flow cytometry. Following withdrawal of treatment, the T level was restored to normalcy within 15 days but 120 days more were required for the animals to exhibit normal sperm counts. In conclusion, the efficacy of once-a-month injection of relatively low doses of NET-EN + E-Val to bring about azoospermia in monkeys, in a relatively short time, has been demonstrated. As the results are uniform and reproducible, it appears desirable that this steroid regimen be tested in man for its contraceptive efficacy.