Infertility: Menstrual Cycle and Cell Nuclear Transfer

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Infertility is the inability or failure to conceive after a year of regular intercourse without contraception. There are two categories to classify infertility, primary and secondary. Primary infertility occurs in women who have never conceived while secondary infertility occurs in women who had a previous conception. Affecting about one in six couples, there are many causes of infertility. A little more than half of cases of infertility are attributed to female conditions. Female conditions include ovulatory dysfunction, tubal or pelvic factors, cervical problems and uterine factors. However, that does not rule out other conditions as well. These include the male factors and unexplained infertility. Male factors are pretesticular causes, testicular factors and posttesticular causes.

Recent research has shown that the increase of infertility in one in ten couples to one in six couples is due to lifestyle factors. Delayed childbearing, habits such as cigarette smoking and alcohol, changes in sexual behaviour and eliminations of most taboos contribute to the increase in infertility in many couples. Cigarette smoke and substance in it such as nicotine has adverse effects on reproduction. It also causes lower circulating levels of estrogen and earlier menopause. For males, smoking decreases sperm quality. Alcohol has found to increase the risk of tubal factor and cervical factor infertility and ovulatory dysfunctions. On males, alcohol is found to increase abnormal shapes in sperm, can lead to impotence, and adversely affect male hormone levels. These lifestyle factors have adverse effects on reproduction as they are found to be able to change the regulation of hormones in both the male and the female, resulting in infertility.

One of the most common female infertility factor is ovulatory dysfunction also known as anovulation, as mentioned eariler. It is a disorder where ovulation does not occur regularly. Causes of ovulatory disfunction range from the disruption of the hormone regulation of the female cycle to the underdevelopment of reproductive organs in a woman, they are mostly related to the imbalance of hormones. It can occur to any woman who has gone through puberty and is common in women approaching menopause, where women stop ovulating. The hypothalamus and pituitary glands in the brain regulates FSH and LH in the beginning of a woman's menstruation cycle, inadequate amounts would cause ovulatory dysfunction. Any changes in the function of the glands would affect ovulation and therefore, many causes of the dysfunction affect the glands in some way.

Premature ovarian failure, a cause of ovulatory dysfunction, is a disorder believed to be due to genetic abnormalies which leads to the faster depletion of eggs in an ovary. Women who have this disorder lose more eggs during menstruation than normal women, eventually leading to early menopause. Hypothyroidism and hyperthyroidism are diseases of the thyroid gland, also are causes of ovulatory dysfunction though it is not very clear how. Hypothyroidism is when the woman does not produce enough thyroid hormone while hyperthyroidism is where too much thyroid hormone is produced. These abnormalies lead to higher amounts of estrogen in a woman, and therefore interfere with the growth of the follicle and affect the amount of FSH and LH that is required for the release of the egg. Polycystic ovary syndrome is a disease which follicles don't mature, causing them to sometimes become ovarian cysts. Women with this disease don't ovulate for periods of time. A suggested theory is that high levels of LH found in these women cause ovulatory dysfunction. Hyperprolactinema is the too much prolactin in a woman's body. Prolactin is a hormone that is needed to produce breast milk and too much of it would cause a decrease in FSH and LH, affecting the maturing of a follicle. It would also disrupt the amount of other hormones needed for ovulation. Eating disorders such as anorexia and...
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