Hyperprolactinemia
Formal Definition
Elevated serum prolactin levels (>20 ng/mL in men, >25 ng/mL in non-pregnant women) causing hypogonadism, galactorrhea, amenorrhea, erectile dysfunction, and infertility; most commonly due to a prolactinoma (lactotroph pituitary adenoma) but can result from hypothyroidism, medications (antipsychotics, metoclopramide, SSRIs), or stalk effect from non-prolactinoma pituitary masses compressing the pituitary stalk.
How It's Used on the Ward
"High prolactin" — causes galactorrhea and irregular periods in women, low libido and ED in men; often discovered incidentally when patients come in for infertility; dopamine agonist (cabergoline) is the treatment.
Example
""27-year-old female with 8 months of amenorrhea, bilateral galactorrhea, decreased libido. Prolactin 85 ng/mL (normal 2-29). TSH normal. MRI reveals 12mm sellar mass consistent with prolactinoma. Diagnosis: macroprolactinoma causing hyperprolactinemia with hypogonadotropic hypogonadism (amenorrhea from suppression of GnRH by excess prolactin). Started cabergoline 0.5mg weekly.""
Clinical Context
Prolactinoma: most common functioning pituitary adenoma (40% of all pituitary adenomas); macroprolactinoma (>10mm) vs microprolactinoma (<10mm). Effects: galactorrhea, amenorrhea/oligomenorrhea (women), decreased libido, erectile dysfunction (men), infertility, bone loss (chronic hypogonadism → osteoporosis). Dopamine agonist = first-line for both micro and macro prolactinomas (even large tumors shrink significantly). Cabergoline preferred over bromocriptine (better efficacy, fewer side effects, twice weekly dosing). Surgery (transsphenoidal) reserved for medication-resistant cases, intolerance to dopamine agonists, or apoplexy. Other causes of elevated prolactin: hypothyroidism (TRH stimulates prolactin), medications (antipsychotics block dopamine → dopamine normally inhibits prolactin → hyperprolactinemia), pregnancy, breastfeeding, stalk effect from non-prolactinoma masses. Macroprolactin (big prolactin, less active) can cause falsely elevated results — PEG precipitation test to identify.