••• Chapter 59^ Disorders of Prolactin Secretion^591
❍ What conclusions can be made based on prolactin serum levels?
- Normal values are generally <25 ng/mL (mg/L).
- Slightly increased values (21–40 ng/mL) may be rechecked as they may reflect response to physiologic stimuli
rather than true hyperprolactinemia. - 20 to 200 ng/mL can be found in any patient with hyperprolactinemia.
250 ng/mL usually indicates the presence of a prolactinoma.
500 ng/mL is diagnostic of a macroprolactinoma (>1 cm in diameter).
1000 ng/mL is suggestive of macroadenomas >2 cm in diameter.
❍ According to the 2011 Endocrine Society Clinical Guidelines, how many prolactin levels should be obtained
to diagnose hyperprolactinemia?
One. A single measurement of prolactin at a level above the upper limit of normal confirms the diagnosis as long as
the serum sample was obtained without excessive venipuncture stress.
❍ True or False: Are dynamic tests of prolactin secretion using TRH, L-dopa, nomifensine, or domperidone
superior to a single prolactin measurement?
False.
❍ What specific medications can cause prolactin levels to be >200 ng/mL?
Risperidone and metoclopramide.
❍ True or False: Do symptoms of hyperprolactinemia correlate with its severity?
True.
- Severe hyperprolactinemia (>100 ng/mL): Typically associated with overt hypogonadism, subnormal estradiol
levels and its consequences: Amenorrhea, hot flashes, and vaginal dryness. - Moderate hyperprolactinemia (50–100 ng/mL) usually causes amenorrhea or oligomenorrhea.
- Mild hyperprolactinemia (20–50 ng/mL) may cause only insufficient progesterone secretion and thus short
luteal phase. Even without menstrual abnormalities these levels of prolactin are associated with infertility.
❍ What is the association between hyperprolactinemia and galactorrhea?
Premenopausal women: Most patients with hyperprolactinemia do not have galactorrhea; most patients who have
galactorrhea have normal prolactin levels.
Postmenopausal women: As they are markedly hypoestrogenemia the galactorrhea is rare. In this group of
patients, hyperprolactinemia is recognized only when adenoma becomes so large that causes headache or visual
disturbances.
❍ What percentage of women with high prolactin levels have galactorrhea?
33%.
❍ What percentage of circulating prolactin is monomeric?
85%. There are “big prolactin” (dimer) and “big big prolactin” (polymeric).
❍ What occurs to the prolactin concentration in pregnant women?
It increases from the normal range 10–25 ng/mL to 200–400 ng/mL, as estrogen suppresses the hypothalamic
dopamine.