Menstrual Irregularities

The Menstrual Cycle

The normal cycle is about 28 days (±7 days), and it is common for the cycle to be of slightly different lengths from month to month. In the first year or two after menarche, it is common to have even more variability, as the body adjusts to menstruation. When a woman experiences cycles within the normal range, it is called eumenorrhea.

The first day of the menstrual bleed is considered Day 1 of the cycle and begins the follicular phase. Normal menstrual bleeding, the shedding of the endometrial lining of the uterus, usually lasts from 3 to 5 days. As menses ceases, hormonal changes lead to the buildup of the endometrial lining again and the growing of follicles in the ovaries. While still part of the follicular phase, this subphase after menses is considered the proliferative phase, when the endometrial lining is thickening and the follicles are growing. Eventually, one follicle dominates, and around Day 14, it releases what becomes a mature ovum, or egg, from the ovary. This is ovulation.

The ovum travels into the fallopian tube, awaiting fertilization, while the endometrial lining develops secretory glands to prepare for implantation. The corpus luteum, what remains of the dominant follicle after the ovum is released, grows and secretes hormones to help maintain the endometrial lining. This is the beginning of the luteal phase or secretory phase, the second half of the menstrual cycle. If the ovum is not fertilized, it disintegrates, as does the corpus luteum; hormone levels fall, and eventually, the endometrial lining is shed (menstruation and Day 1 of the next menstrual cycle).

There are a variety of hormonal changes that occur during the menstrual cycle. Pulsatile secretion of gonadotropin-releasing hormone (GnRH) [Page 864]from the hypothalamus (an organ in the brain) stimulates the production of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the pituitary gland (another organ in the brain), which affects the levels of important hormones involved in the menstrual cycle, including estrogen and progesterone. The menstrual cycle is a complex positive and negative feedback system of an array of hormones and endocrine glands.

Importance of Normal Menstrual Function

Normal hormone levels are important for bone health, fertility, cardiovascular health, and other biological functions. For example, women attain 90% of their peak bone density by the time they are 18 years of age. If menstrual cycles do not occur during adolescence, a significant opportunity for bone building will be lost, putting the individual at much higher risk for fractures immediately and later in life. Thus, abnormal menstrual cycles should always be investigated. First and foremost, they may signify pregnancy! But they may also signify lack of nutrition, excessive exercise, polycystic ovarian syndrome, a thyroid disorder, uterine polyps, fibroids, endometrial fibroids, diabetes, a drug effect, infection, or other health problems. The following are signs that a female should see her doctor about her menstrual

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