Menstrual cycle hormonal fluctuations

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. 

To explain further the intricacies of the normal menstrual cycle, the fluctuations of each major hormone are discussed separately in the following sections with regard to control and effects (see also Figures 53-7 and 53-14). 

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

For low therapeutic/toxic drugs such as lithium, this might prove to be an explanation of the reduction in efficacy seen at the end of the menstrual cycle, when these hormone levels fall (Conrad and Hamilton, 1986). It might also explain the reduction in efficacy of other central nervous system drugs such as antiepileptics (Shavit et al., 1984 Roscizeweska et al., 1986) and antimigraine medications, seen with the fluctuation of the menstrual cycle (Gengo et al., 1984). 

Fluctuations in hormones and neurotransmitters during the luteal phase of the menstrual cycle, postpartum period, and during peri-menopause (starting approximately 10 years before menopause) may precipitate mood changes and increase cycling that resembles bipolar II disorder. Women with bipolar I disorder are at greater risk for relapse into mania, depression, or psychosis during the... 

Abnormalities in calcium or parathyroid hormone homeostasis may be a factor in depression. Significant fluctuations in calcitonin, a calcium-regulating hormone, and low plasma calcium levels during the menstrual cycle may play a part in the etiology of PMS. Calcium influx into brain cells is involved with the release of many neurotransmitters. Calcium supplementation (e.g., 1200-1600 mg/day of calcium carbonate in two divided doses) has been shown to reduce premenstrual symptoms such as anxiety, depression, irritability, mood swings, headache, fluid retention, and cramps. " " Calcium supplementation may help to prevent osteoporosis later in life, and it is a relatively safe and inexpensive treatment. ... 

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.)... 

Uterine cervical secret was examined by the Brdidka filtrate reaction in the course of the menstrual cycle it exhibits regular fluctuation with a minimum at the culmination of the proliferation phase, and a maximum during the secreting phase. This examination was influenced by the administration of hormonal preparations a decrease was observed after an estrogen (diethylstilbestrol), and an increase after a gestagen (ethisterone) (243). 

Synthesis of lutropin and follitropin is controlled by gonadotropin releasing hormone from the hypothalamus, which in turn is influenced by the sexual center in the brain. The sexual center, hypothalamus, anterior lobe of the pituitary and gonads or ptecenta form a feedback loop in which the sex hormones from the gonads exert negative feedback on the brain. Females display a cycUc pattern of variation in the hormone levels (menstrual cycle). In males, the variations are acyclic. In addition to these long-term variations, there are diurnal fluctuations in the hormone levels. 

Circulating hormones, such as aldosterone and renin have long been known to fluctuate with the menstrual luteal phase. If an amenorrheic cycle occurs, these changes are not seen (Michelakis et al, 1975). If oral contraceptives are given, then an increase of these hormones is also seen in the... 

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