Uterine cycle

In exposed women, possible disruptions of the neurohormonal-endocrine balance necessary for normal ovarian and uterine cycles may lead to amenorrhea, abnormal menstrual cycles, spontaneous abortions, and even sterility (WHO 1979 Zielhuis et al. 1984). Serum thyroxine levels, which decrease following carbon disulfide exposure, have also been suggested as a biomarker (Cavalleri 1975). 

FIGURE 6.21.6 The menstrual cycle in humans, (a) Fluctuation of gonadotropin levels, (b) Fluctuation of ovarian hormone levels, (c) Ovarian cycle, (d) Menstrual cycle (uterine cycle). (From Campbell, N.A. et al.. Biology, 5th edn., Addison Wesley Longman, Menlo Park, CA, 1999. With permission.)... 

Fig.l FSH and LH secretion during the menstrual cycle. The upper panel represents the ovarian cycle and shows changes occurring in the follicles. The lower panel represents the uterine cycle and shows changes in the endometrial lining of the uterus. 

Thus, it appears that the uterine cycle in non-pregnant and in pregnant conditions is controlled by the operation of two distinct groups of hormones, as shown in the following diagram (Jeffcoate, 1935). 

F (decreased mating and fertility indices, abnormal estrous cycle, decreased uterine weight)... 

Fig. 12.1. Variation (%) from baseline in uterine and leiomyoma sizes and in A size after 3, 6, 9, and 12 cycles of treatment. Values are reported as mean SD.a p < 0.05 vs. baseline. A = group A = group B (Palomba et al. 2001). Permission to publish from Elsevier...

Table 12.2. Number and percentage of women with unmodified, decreased, and increased uterine and leiomyoma sizes after 3 and 6 cycles of 60 mg/d raloxifene (group A), 180 mg/d raloxifene (group B), and placebo (group C) (Palomba et al. 2002a)... 

Raloxifene is actually used for the treatment and prevention of postmenopausal osteoporosis. Also, if raloxifene has been shown to have any effect on uterine leiomyomas in vitro and in animal models, to date no concrete efficacy has been demonstrated in normally cycled premenopausal women. Moreover, the addition of raloxifene to GnRH-a administration can be useful for limiting GnRH-a-related side effects and increasing the rate of reduction in tumor size. 

Kawaguchi K, Fujii S, Konishi I, Nanbu Y, Nonogaki H, Mori T (1989) Mitotic activity in uterine leiomyomas during the menstrual cycle. Am J Obstet Gynecol 160 637-641... 

In the human, the uterus lies like an inverted pear in the pelvis. The wall of the uterus consists of three layers a thin outer layer, the perimetrium a middle muscular layer, the myometrium and an inner glandular mucosa, the endometrium, which lines the uterine cavity. Once the ovum is fertilised, the zygote undergoes several cell cycles (Chapter 20) to form a rounded mass of cells, the blastocyst, which passes into the uterus where it implants in the wall (see below). 

Estradiol is the most important of the estrogens. Like progesterone, it is synthesized by the ovaries and, during pregnancy, by the placenta as well. Estradiol controls the menstrual cycle, it promotes proliferation of the uterine mucosa, and is also responsible for the development of the female secondary sexual characteristics (breast, fat distribution, etc.). 

Progestins are nsed for varions menstmal cycle disorders, for functional uterine bleeding of various origins, and as a contraceptive. Progestin therapy is also used to treat endometriosis and endometrial carcinomas. Progesterone is not effective when taken orally due to intensive metabolism, and therefore it is used by either parenteral or transvaginal introduction. 

Secondary amenorrhea abnormal uterine bleeding due to hormonal imbalance in the absence of organic pathology - 2.5 to 10 mg/day for 5 to 10 days during the second half of the theoretical menstrual cycle. Withdrawal bleeding usually occurs within 3 to 7 days. 

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