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Amenorrhea : LABORATORY AND DIAGNOSTIC STUDIES

Pregnancy Test

Urine or serum testing for the beta subunit of the human chorionic gonadotropin (b-hCG) is used to identify or rule out pregnancy, and is an essential test on all females presenting with amenorrhea.


Thyroid-Stimulating Hormone

A serum TSH test identifies hypothyroidism. When hormonal supplementation is provided, menses usually resume for these patients. If the amenorrhea is associated with galactorrhea and hyperprolactinemia, the prolactin level must be measured again after the thyroid function levels become normal.


Prolactin Levels

About one-third of women with no obvious cause of amenorrhea will have an elevated prolactin level. When the patient’s fasting prolactin level is within reference range, less than 50 ng/mL, a progesterone challenge test is indicated. If the fasting prolactin level is high, greater than 50 ng/mL, or if the patient has galactorrhea, a cone-down view of the sella turcica is taken to rule out a pituitary adenoma. A level greater than 200 ng/mL, is highly suggestive of a prolactinoma. A prolactin elevation less than 100 ng/mL, but higher than normal, is most frequently caused by prescribed or illicit drugs. The hyperprolactinemia usually subsides a few weeks after stopping the offending drug. Prolactin levels are normal in PCOS. Microscopic examination of breast discharge will reveal fat globules and no red blood cells (see Chapter 6).


Serum Follicle-Stimulating Hormone Levels

Ovarian failure, which causes a low estradiol secretion, will raise the FSH level higher than 40 milliunits/mL. If both the FSH and LH levels are greater than 50 milliunits/ mL, then primary ovarian failure is established. If the patient is older than 30 years, menopause is diagnosed; if she is younger than 30 years, a karyotype should be done. An FSH measurement of less than 40 milliunits/mL denotes a hypothalamic-pituitary dysfunction and secondary ovarian failure.


Serum Luteinizing Hormone Levels

A serum LH level greater than 35 milliunits/mL is frequently seen in patients with PCOS. An LH:FSH ratio higher than 2:1 is suggestive of PCOS, whereas a ratio higher than 3:1 is considered diagnostic of PCOS.


Dehydroepiandrosterone Sulfate


Mildly elevated levels of dehydroepiandrosterone sulfate (DHEA-S) are seen in women with PCOS. A significantly elevated level of DHEA-S, greater than 700 mg/dL, indicates congenital adrenal hyperplasia.


Central Nervous System Imaging

If both FSH and LH levels are low, indicating a problem of the pituitary, imaging of the CNS is warranted. Either contrast-enhanced CT or MRI of the sella turcica can determine whether there is an abnormality. If the prolactin level is greater than 100 ng/mL, or the cone-down view of the sella turcica is abnormal, CT or MRI with contrast enhancement should be obtained.


Pelvic Ultrasound and Vaginal Ultrasound

Pelvic and vaginal ultrasound studies are used to determine the presence of a uterus, the anatomical size and endometrial thickness of a uterus, and whether fibroids or other tumors exist. Ultrasound is used to measure ovarian size, to identify cysts, and to evaluate follicular development. In primary amenorrhea, ultrasound is helpful in assessing müllerian agenesis and gonadal dysgenesis, because there could be internal organs and no conduit to the perineum. One-third of these patients also have urinary tract abnormalities; therefore an abdominal ultrasound can be obtained at the same time to evaluate that system.


Progesterone Challenge Test

Also called the progesterone withdrawal test, the progesterone challenge test (PCT) consists of the administration of oral DMPA 10 mg daily for 7 to 10 days, or parenteral progesterone in oil 200 mg intramuscularly. The patient should respond to the medication within 2 to 7 days. If there is a positive PCT response, the patient bleeds. This demonstrates that there are sufficient endogenous estrogens to prepare the endometrium and confirms that there is a functioning outflow tract. It substantiates an intact HPO axis. Other forms of progesterone can be used: micronized progesterone 400 mg orally daily for 7 to 10 days, or norethindrone 5 mg orally daily for 7 to 10 days.


Estrogen/Progesterone Challenge Test

The estrogen/progesterone challenge test (E/PCT) consists of the administration of conjugated estrogens 1.25 mg daily, or estradiol 2 mg daily for 21 days, followed by progesterone as given in the PCT. If there is no menstrual flow, administer the regimen a second time. If there is no flow after both courses of therapy, the cause is either the outflow tract or the uterine endometrium. The E/PCT is positive if there is menstrual flow within 2 to 7 days. A positive test denotes that there is inadequate estrogen production either from inadequate functional ovarian follicles, or from inadequate pituitary gonadotropic stimulation.


Chromosome Analysis (Karyotyping)

Karyotyping is done to delineate probable chromosomal abnormalities. It is used in the workup for ambiguous genitalia, primary amenorrhea, oligomenorrhea, delayed puberty, or abnormal development at puberty.


Endometrial Biopsy

Endometrial biopsy can be used to show the hormonal response of the uterine endometrium.


Basal Body Temperature Charting

A woman can take her awakening body temperature each day and chart it to determine if ovulation is occurring. This test is based on the fact that progesterone increases the body temperature by 0.5° F to 0.8° F for 11 days during the luteal phase. If this increase in temperature occurs, ovulation has occurred and a positive estrogen component is inferred.


Maturation Index

The maturation index indicates the degree of maturation of the vaginal epithelium and provides an objective assessment of vaginal hormone response as well as overall hormonal environment. The sample is collected by scraping the vaginal wall near the cervix. The index is read from left to right and refers to the percentage of parabasal, intermediate, and superficial squamous cells appearing on a smear, with the total of all three values equaling 100%. For example, an MI of 0/40/60 represents 0% parabasal cells, 40% intermediate cells, and 60% superficial cells. Lack of estrogen effect is demonstrated by the predominance of parabasal cells. Low estrogen effect is demonstrated by the predominance of intermediate cells. Increased estrogen effect is demonstrated by the predominance of superficial cells. Both increased and decreased estrogen effects can be reflective of a hormonal imbalance of the HPO axis.


Progesterone Levels

Serum progesterone levels collected at weekly intervals can establish whether ovulation has occurred. A value greater than 3 ng/mL is found with ovulation.