Menstrual cycle, hormones

In order to maintain homeostasis or to repeat physiologic processes such as the menstrual cycle, hormone levels must be regulated. 

Ovariectomized (ovx) cynomolgus monkeys represent a common model for postmenopausal osteoporosis because they experience regular menstrual cycles, hormonal fluctuations and bone loss upon ovariectomy. Both, ovx monkeys and postmenopausal osteoporotic women showed similar modifications in trabecular mineral properties [65], specifically a decreased mineral matrix ratio, increased crystallinity and increased carbonate content relative to controls. In addition, the spatial variation in the mineral matrix ratio was the same in humans and monkeys. 

Smith CG, Almirez RG, Scher PM, Asch RH. 1984. Tolerance to the reproductive effects of A -tetrahydro-cannabinol. Comparison of the acute, short-term, and drug chronic effects on menstrual cycle hormones, in Agurell S, Dewey W, Willette R., Eds. The Cannabinoids Chemical, Pharmacologic and Therapeutic Aspects. New York Academic Press, pp. 471 485. 

In contrast to the uterine corpus, the uterine cervix shows only little variation of its zonal anatomy as depicted by MRI with age, phase of the menstrual cycle, hormone replacement therapy, or use of oral contraceptives. 

Testosterone promotes muscle growth deepening of the voice the growth of body hair and other male secondary sex characteristics Testosterone is formed from cholesterol and IS the biosynthetic precursor of estradiol the principal female sex hormone or estrogen Estradiol is a key substance m the regulation of the menstrual cycle and the reproductive process It is the hormone most responsible for the development of female secondary sex characteristics... 

Taking the contraceptive hormones provides health benefits not related to contraception, such as regulating the menstrual cycle and decreased blood loss, and incidence of iron deficiency anemia, and dysmenorrhea Health benefits related to the inhibition of ovulation include a decrease in ovarian cysts and ectopic pregnancies. hi addition, there is a decrease in fibrocyctic breast disease, acute pelvic inflammatory disease endometrial cancer, ovarian cancer, maintenance of bone density, and symptoms related to endometriosis in women taking contraceptive hormones. Newer combination contraceptives such as norgestimate and ethinyl estradiol... 

The female menstrual cycle is divided into four functional phases follicular, ovulatory, luteal, and menstrual.6 The follicular phase starts the cycle, and ovulation generally occurs on day 14. The luteal phase then begins and continues until menstruation occurs.6 The menstrual cycle is regulated by a negative-feedback hormone loop between the hypothalamus, anterior pituitary gland, and ovaries6 (Fig. 45-1). 

FIGURE 46-2. Hormonal fluctuations with the normal menstrual cycle. (Reprinted, with permission, from ref. 3.)... 

Women who have been in contact with toxafene have an increased estrogen level in the initial period of the menstrual cycle. Moreover, there was no clear phase change, which shows that hormonal regulation was disrupted [15]. The negative impact of even low doses of OCPs on pregnancy has been proved, especially in the third trimester [1]. It has been shown many times that there is a correlation between embryo death and pesticide content in the mother s body [1]. We will now quote several results of the study of pesticides effects on pregnancy and birth. 

The progestin-only Minipills tend to be less effective than combination OCs, and they are associated with irregular and unpredictable menstrual bleeding. They must be taken every day of the menstrual cycle at approximately the same time of day to maintain contraceptive efficacy. They are associated with more ectopic pregnancies than other hormonal contraceptives. 

Medical treatment of endometriosis has focused on the hormonal alteration of the menstrual cycle in an attempt to produce a pseudopregnancy, pseudomenopause, or chronic anovulation (Olive et al. 2001). 

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