Be a Pro at Prolactin: Updated recommendations

When it comes to hormones, prolactin doesn’t get much of the spotlight until it starts causing surprises like irregular periods, galactorrhea, or low libido. Here’s what to check, when to recheck, and when referral is indicated.

Serum prolactin levels should only be measured when clinically indicated, such as in cases of infertility, menstrual irregularities, low libido, erectile dysfunction, or unexplained galactorrhea. 

Normal prolactin levels are under 25 μg/L in females and under 20 μg/L in males (but fortunately on the CCFP exam, normal values are provided)

Hyperprolactinemia has a broad differential diagnosis, including pregnancy, medications, hypothyroidism, renal or liver failure, and pituitary or hypothalamic disorders. It is particularly common in people with amenorrhea or abnormal uterine bleeding.

Mild asymptomatic hyperprolactinemia (20–200 μg/L) is often transient or due to macroprolactinemia—a benign, inactive form of the hormone. Repeat testing after 2–4 weeks, along with pregnancy testing and screening for macroprolactin, is advised before pursuing further investigations.

SNAP SAMP A 34-year-old male gets screening lab tests from a naturopath and their prolactin is found to be 150 μg/L (normal < 20 μg/L). He has no symptoms or visual defecits. What is the BEST next imaging step for this patient? a) MRI brain b) CT brain c) Ultrasound brain c) none Answer at the end

Marked prolactin elevation (> 200 μg/L) may suggest a prolactinoma, particularly in the absence of prolactin-elevating medications. In such cases, further assessment for pituitary function and visual symptoms is warranted, with specialist referral. Prolactin levels generally correlate with tumor size. If hyperprolactinemia is accompanied by visual deficits, urgent imaging and referral to endocrinology and neurosurgery are required, as a pituitary macroadenoma affecting the optic chiasm may be present.

Take a FULL medication history

Antipsychotic medications are a frequent cause of elevated prolactin, with first-generation agents and some second-generation drugs (e.g., risperidone) leading to significant elevations. When antipsychotics are involved and symptoms are present, endocrinology consultation is recommended to help differentiate drug-induced changes from underlying pathology. SNAP SAMP Answer The answer according to the CMAJ article is c) none. Routine neuroimaging should be avoided in asymptomatic, mild asymptomatic hyperprolactinemia (20–200 μg/L) to prevent unnecessary testing and incidental findings.

Source: CMAJ