Normal Menstrual Cycle

Bromocriptine directly binds to the D2 receptors on the lac-totroph cells to exert its effect. Bromocriptine normalizes prolactin level, restores menstrual cycles, and reduces tumor size in approximately 90% of patients.49 Adverse effects such as nausea, dizziness, and orthostatic hypotension often limit 5% to 10% of patients from continuing treatment. Thus, start bromocriptine at a low dose (e.g., 0.625-1.25 mg) at bedtime... 

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

Therapeutic modalities for amenorrhea are targeted at restoring the normal menstrual cycle. The goals of treatment are to preserve bone density, prevent bone loss, and restore ovulation, thus improving fertility as desired. Amenorrhea resulting from conditions contributing to hypoestrogenism also may affect quality of life via the induction of hot flashes (premature ovarian failure), dyspareunia, and in prepubertal females, lack of secondary sexual characteristics and absence of menarche. 

Cancer antigen 125 (CA-125). The normal level is less than 35 units/mL (35 kU/L). This test is associated with a lack of specificity. CA-125 can be elevated in a number of other states, such as different phases of the menstrual cycle, endometriosis, and non-gynecologic cancers. It is important to rule out other cancers associated with the abdominal cavity. 

The effects of raloxifene in premenopausal women have been analyzed in subjects with normal ovarian function treated with high doses (100 to 400 mg daily) at either different time points of their menstrual cycle or continuously for 4 weeks (Baker et al. 1998). Raloxifene did not prevent ovulation, nor did it alter the length of the menstrual cycle or the day of the LH surge. However, it did stimulate FSH secretion, increase serum estradiol levels, and decrease serum PRL. These results are also similar to those reported for premenopausal women taking tamoxifen (Jordan et al. 1991) and are indicative of some antiestrogenic action at either the hypothalamic and/or pituitary level. 

Horowitz M, Maddern GJ, Chatterton BE, Collins PJ, Petrucco OM, Seamark R, Shearman DJ. The normal menstrual cycle has no effect on gastric emptying. Br J Obstet Gynaecol 1985 92 743-746. 

Gonadotropins are used to treat infertility in women with potentially functional ovaries who have not responded to other treatments. The therapy is designed to simulate the normal menstrual cycle as far as is practical. A common protocol is daily injections of menotropins for 9 to 12 days, until estradiol levels are equal to that in a normal woman, followed by a single dose of hCG to induce ovulation. Two problems with this treatment are risks of ovarian hyperstimulation and of multiple births. Ovarian hyperstimulation is characterized by sudden ovarian enlargement associated with an increase in vascular permeability and rapid accumulation of fluid in peritoneal, pleural, and pericardial cavities. To prevent such occurrences, ovarian development is monitored during treatment by ultrasound techniques and by measurements of serum levels of estradiol. 

Results from a clinical trial of cabergoline in women with hyperprolactinemia and anovulation. A The dotted line indicates the upper limit of normal serum prolactin concentrations. B Complete success was defined as pregnancy or at least two consecutive menses with evidence of ovulation at least once. Partial success was two menstrual cycles without evidence of ovulation or just one ovulatory cycle. The most common reasons for withdrawal from the trial were nausea, headache, dizziness, abdominal pain, and fatigue. 

In normal women, estradiol is produced at a rate that varies during the menstrual cycle, resulting in plasma levels as low as 50 pg/mL in the early follicular phase to as high as 350-850 pg/mL at the time of the preovulatory peak (Figure 40-1). 

The corpus luteum arises from the ruptured follicle and secretes progesterone, which has an important role in the estrous or menstrual cycle. Luteal progesterone is also required to maintain early pregnancy in most mammalian species, including humans (Csapo Pulkkinen, 1978). Therefore, establishment and maintenance of normal corpora luteaare essential for normal reproductive function. However, with the exception of evaluations to establish their presence or absence, these structures are not evaluated in routine testing. Increased rates of follicular atresia and oocyte toxicity may lead to premature menopause in humans. Altered follicular development, failure to ovulate or altered corpus luteum formation and function can disrupt cyclicity, reduce fertility and interfere with normal sexual behaviour. Therefore, significant increases in the rate of follicular atresia, evidence of oocyte toxicity, interference with ovulation or altered corpus luteum formation or function should be considered adverse effects. 

Gender is not an important determinant of plasma amino acid levels. Females have a tendency toward small changes of their amino acid levels during the menstrual cycle. However these changes are barely distinguishable from the normal diurnal changes and dietary influences. 

The clinical value of pregnanediol determination is found in gynecological disorders, in cases of abnormal pregnancies, and as evidence of actively secreting corpus luteum and ovulation during the normal menstrual cycle. 

Body temperature tends to rise slightly in some users of oral contraceptives (286,287) Progesterone has a mild thermogenic effect, reflected in changes in body temperature during the normal menstrual cycle. Mild pyrexia in users of oral contraceptives may reflect this, but the patient should always be examined to exclude infection. 

---