At a Glance
Approximately 1% of women of reproductive age experience secondary amenorrhea, a cessation of menses. In women who previously experienced regular menstrual cycles, secondary amenorrhea is the absence of menstruation for 6 months. In women who previously experienced irregular menstrual cycles, secondary amenorrhea is the absence of menstruation for 12 months. Secondary amenorrhea is a symptom caused by many pathological states, including pregnancy, polycystic ovary syndrome (PCOS), Cushing’s syndrome, hypopituitarism, hypothyroidism, and hyperprolactinemia. Some patients do not demonstrate an obvious etiology for their amenorrhea; however, the diagnostic evaluation should lead to the correct diagnosis if the problem is approached in a logical, stepwise manner.
In diagnosing the underlying cause of amenorrhea, the first step should always be to rule out pregnancy with a negative urine or serum hCG result. Next, levels of thyroid stimulating hormone (TSH), prolactin, luteinizing hormone (LH), and follicle-stimulating hormone (FSH) should be ordered. Basal levels of these hormones narrow the differential.
In women of child-bearing age, low levels of LH/FSH and decreased estradiol are sufficient to confirm a diagnosis of hypopituitarism. However, LH and FSH levels can be suppressed by an elevated prolactin, so they should not be interpreted unless prolactin is low or normal. Additionally, TSH levels can be suppressed because of hypopituitiarism or in response to hyperthyroidism. Therefore, basal levels of TSH and thyroxine (T4) are required to confirm hypopituitarism (Table 1).
|Low||Low or Normal||Low||Low||Low||Low|
Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results?
Levels can be affected by drugs, including aspirin, prednisone, potassium iodine, lithium, dopamine, and amiodarone.
Levels can appear falsely increased in patients with anorexia nervosa or those who are taking drugs like estrogen, tricyclic antidepressants, opiates, amphetamines, hypertension drugs (e.g., reserpine, verapamil, methyldopa), and cimetidine.
Levels can appear falsely decreased by drugs like levodopa, dopamine, and ergot alkaloid derivatives.
Levels can appear falsely elevated in patients taking anticonvulsants, naloxone, and clomiphene.
Levels can appear falsely decreased in patients who are taking oral contraceptives (or other hormonal treatments) or digoxin.
Levels can appear falsely elevated in patients who smoke or take cimetidine, clomiphene, digitalis, or levodopa.
Levels can appear falsely decreased in patients who are taking oral contraceptives (or other hormonal treatments) or phenotiazines.
Levels are subject to daily and cycle-dependent variation. Additionally, glucocorticosteroids, ampicillin, and tetracyclines can increase estrogen levels in the blood. Levels can be decreased by oral contraceptives.
What Lab Results Are Absolutely Confirmatory?
In women of child-bearing age, low levels of LH/FSH in the presence of low to normal prolactin and decreased estradiol are sufficient to confirm a diagnosis of hypopituitarism.
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- At a Glance
- Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?
- What Lab Results Are Absolutely Confirmatory?