Menstruation is the periodic discharge of blood and mucosal tissue from the uterus, which occurs approximately monthly in nonpregnant women from the onset of puberty to menopause and is necessary for female reproduction. Menarche, or the first menstrual period, occurs during puberty and signals the onset of the reproductive years of a woman. On the other end of the spectrum, the beginning of menopause is when there have been no menstrual periods for 12 consecutive months and no other biological or physiological cause can be identified. Between these two end points, women would ideally have normal, regular menstrual cycles, or eumenorrhea, that range from 21 to 35 days in length.

Menstrual cycles are counted from the first day of menstrual bleeding because the onset of menstruation corresponds closely with the hormonal cycle. The menstrual cycle may be divided into several phases and the length of each phase varies from woman to woman and cycle to cycle. During the follicular phase, estrogen slowly builds up. Meanwhile, the follicle matures. Estrogen peaks right before ovulation, or the release of the egg from the ovary. The surge of luteinizing hormone (LH) triggers ovulation. The egg travels through the fallopian tube and may be fertilized by a sperm in the process. If the egg is not fertilized within a day of ovulation, it dies and is resorbed. During the luteal phase, the corpus luteum, or the remainder of the follicle postovulation, produces progesterone, causing the intrauterine lining to accumulate. Once the corpus luteum degenerates and progesterone levels decline, the uterine lining is shed, indicating the start of the menstrual cycle.

Menstrual problems are characterized by the irregularity of menstrual cycles, or the unpredictable variability of intervals, duration, or bleeding. With regard to irregularities in ovulation, oligoovulation is the term for infrequent or irregular ovulation, defined as cycles of more than 36 days or fewer than 8 cycles a year. Anovulation is the absence of ovulation when it would be normally expected, such as in a postmenarchal, premenopausal woman. Patients with anovulation usually present with the irregularity of menstrual periods. Additionally, anovulation can also cause cessation of periods, also called secondary amenorrhea, or excessive bleeding, as characterized by dysfunctional uterine bleeding.

In terms of menstrual cycles, polymenorrhea refers to cycles with intervals of 21 days or less. Another condition is oligomenorrhea, defined as infrequent or light menstrual cycles with more than 35 days. Occurring in approximately half of patients with bulimia nervosa, the mechanism of oligomenorrhea appears to be related to hypothalamic-pituitary function.

Similarly, amenorrhea is a diagnostic criterion for anorexia nervosa. Amenorrhea is the absence of a menstrual period in a woman of reproductive age. Physiologic states of amenorrhea are seen during pregnancy and lactation, or breastfeeding.

In patients with anorexia, the exact mechanism of amenorrhea has yet to be elucidated. Nonetheless, severe caloric restriction suppresses the hypothalamic-pituitary axis, possibly mediated by cortisol, leptin, growth hormone, and insulin-like growth factor I, resulting in the suppression of the pituitary production of LH and FSH. Abnormally low levels of LH and FSH cause low levels of circulating estrogen, thereby blocking ovulation.

Because estrogen is essential for the incorporation of calcium into bone, patients with eating disorders such as anorexia are at high risk of developing osteopenia and osteoporosis. Particularly, certain patients with eating disorders may also exercise excessively, increasing their risk of stress fractures. The female athlete triad consists of a menstrual disorder, an eating disorder, and osteoporosis.

A common cause of ovulatory infertility is polycystic ovarian syndrome (PCOS), affecting 1 to 5 percent of women. PCOS is characterized by hyperandrogenism and chronic oligoanovulation. Approximately 50 percent of PCOS women are overweight or obese, with adipose tissue distribution predominately around the abdomen as a common clinical presentation. Because the history of weight gain often precedes PCOS, obesity may play a pathogenic role in the development of the syndrome. Administration of insulin-sensitizing agents, such as metformin and troglitazone, was associated with improved menstrual cyclicity in women with PCOS. Both insulin and insulin-like growth factors (IGFs) seem to be involved in the interruption of the normal follicle maturation favoring the formation of atretic follicles. Therefore, obesity seems to amplify the degree of insulin resistance and hyperinsulinemia in PCOS, whereas abnormalities of the IGF-insulinlike growth factor binding protein (IGFBP) system may be important in normal-weight PCOS women.

Additionally, women with PCOS may have hyperandrogenism, which is worsened by particularly central obesity, through the reduction of sex hormone-binding globulin (SHBG) serum levels, which increases the delivery of free androgens at the level of peripheral tissues. High levels of estrogens have been detected in women with PCOS. The acyclic production of extraglandular estrogen may lead to a positive feedback on LH secretion and a negative feedback on FSH secretion, resulting in an increase of the circulating LH/FSH ratio. The elevated levels of LH substantially contribute to the development of hyperplasia of the ovarian stroma and thecal cells, further increasing androgen production and, in turn, providing more substrate for extraglandular aromatization and perpetuation of chronic anovulation.

With respect to nutrition and environmental factors, diet is a well-established factor in the regulation of sex steroid metabolism. Research has shown that the high-fat, low-fiber diet is related to an increase in androgen circulating levels. Additionally, evidence finds that very high lipid intake decreases SHBG blood levels and increase free androgen index. Therefore, a high-fat, lower-fiber diet may impair sex steroid metabolism by increasing androgen availability while favoring the promotion and maintenance of obesity in certain groups of women with PCOS.

Free term papers are not written to satisfy your specific instructions. You can use our professional writing services to buy a custom written research paper, term paper, or essay on Obesity at affordable price. CustomTermPapers is the best solution for those who seek help in writing term papers, essays, and research papers related to Obesity and other relevant topics.