Likely Diagnosis

1. Stress/sampling artifact - venipuncture stress, non-fasting sample, or a sample drawn after breast stimulation/exercise/sexual activity can transiently raise prolactin. Mild elevations should always be confirmed by a repeat fasting morning sample.
2. Idiopathic hyperprolactinemia - no identifiable cause found even after work-up; common in young women with this degree of elevation.
3. Microprolactinoma (small pituitary adenoma) - the classic cause once other causes are excluded; levels of 30-100 ng/mL are typical for microadenomas, while levels >200 ng/mL strongly suggest a macroadenoma.
4. Drug-induced - antipsychotics, some antidepressants (SSRIs), metoclopramide/domperidone, verapamil, opioids, and estrogen-containing contraceptives are common culprits. Worth a careful medication history.
5. Subclinical/mild hypothyroidism - compensatory TRH rise can elevate prolactin; confirm TSH is truly normal.
6. PCOS - roughly 15-20% of PCOS patients have mild hyperprolactinemia along with irregular menses; worth screening (androgens, ovarian morphology) if not already done.
7. Pituitary stalk compression from a nonfunctioning mass (less likely if imaging/other pituitary hormones are normal).

Recommended Work-up

• Repeat fasting, morning prolactin (avoid breast exam/sex 24h prior) to confirm true elevation.
• Review all medications/supplements for dopamine-antagonist effects.
• Confirm TSH and renal function are truly normal (if not already checked with a sensitive assay).
• Pituitary MRI if the repeat level stays elevated, especially if >100 ng/mL, or if there are headaches, visual field changes, or galactorrhea - this rules in/out a microadenoma.
• Screen for PCOS features (androgens, pelvic ultrasound) if irregular menses persist and prolactin is only mildly elevated.

Treatment

• If mild and asymptomatic aside from cycle irregularity, some clinicians simply observe with periodic prolactin monitoring, since many cases normalize spontaneously and microadenomas rarely enlarge.
• If it is causing troublesome menstrual irregularity, galactorrhea, or she wants to conceive, treat with a dopamine agonist:
  • Cabergoline 0.25 mg twice weekly (preferred - better tolerated, more effective) titrated to normalize prolactin, or
  • Bromocriptine 1.25-2.5 mg at bedtime, titrated up.
  • Recheck prolactin every 2-4 weeks and adjust to the lowest effective dose; menses and fertility typically return once prolactin normalizes, so contraception should be discussed if pregnancy is not desired.
  • A 2025 systematic review/network meta-analysis (PMID 39411853) confirms cabergoline has the best efficacy/tolerability profile among dopamine agonists for hyperprolactinemia, consistent with the textbook guidance above.
• If a drug is the culprit, stop or switch it if clinically feasible.
• If a macroadenoma or hypothalamic lesion is found on imaging, refer to endocrinology for further evaluation of the rest of the pituitary axis.

• First-line: NSAIDs (ibuprofen, mefenamic acid, or naproxen) started at onset of menses or pain, which block prostaglandin synthesis.
• Second-line: combined oral contraceptives, which also help regulate irregular cycles - a useful dual-purpose option here once hyperprolactinemia is addressed (note: estrogen-containing pills can itself mildly raise prolactin, so this should be timed/discussed with the treating physician).
• Levonorgestrel IUD is an effective alternative if NSAIDs/OCPs fail or aren't desired.
• If pain persists despite these measures, pelvic ultrasound to exclude secondary causes (endometriosis, fibroids) should be considered even though initial tests were normal.