Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

MGFT
60030
symptoms of hyperprolactinemia are absent, or pituitary imaging studies are not informative.
Useful For: Determining biologically active levels of prolactin, in asymptomatic patients with elevated
prolactin levels Ruling out the presence of macroprolactin
Interpretation: When the percentage of the precipitated prolactin (complexed) fraction of total
prolactin is or
=50%, the specimen is considered positive for the presence of macroprolactin. Following macroprolactin
precipitation, a patient whose unprecipitated prolactin level is greater than the upper limit of the total
prolactin reference range may have hyperprolactinemia. See PRL/8690 Prolactin, Serum for interpretation
of prolactin levels.
Reference Values:
TOTAL PROLACTIN
Males
< or =18 years: not established
>18 years: 4.0-15.2 ng/mL
Females
< or =18 years: not established
>18 years: 4.8-23.3 ng/mL
Percent of the precipitated (complexed) prolactin fraction of the total prolactin 30 mEq/24
hour), with an osmotic gap >100 mOsm/kg, magnesium is likely to be the principle contributor to osmotic
diarrhea. Use of magnesium salts in the form of over-the-counter stool softeners is the most likely source
of such excess excretion.
Useful For: Diagnosis of osmotic diarrhea due to excessive ingestion of magnesium Ruling out
excessive ingestion of magnesium in the work-up of chronic diarrhea
Interpretation: The osmotic theory of diarrhea is explained by the equation: 2x (stool sodium + stool
potassium) = stool Osmolality + or - 30 mOsm. Normal fecal sodium and potassium in the presence of an
osmotic gap (>30 mOsm/kg) suggests osmotic diarrhea. Ingestion of more than usual dietary magnesium
leading to increased excretion of fecal magnesium contributes to osmotic diarrhea. Magnesium excretion
at >30 mEq/24 hour is frequently associated with decreased fecal sodium and potassium, and is an
indicator of excessive consumption of magnesium that is likely the cause of diarrhea.
Reference Values:
0-15 years: not established
> or =16 years: 0-29 mEq/24 hour
Clinical References: 1. Phillips S, Donaldson L, Geisler K, et al: Stool composition in factitial
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