Why check prolactin levels in a 45-year-old female?

Checking Prolactin in a 45-Year-Old Woman

Prolactin measurement should be offered in a 45-year-old woman presenting with menstrual disturbances, galactorrhea, visual field loss, or symptoms of hypogonadism, as these may indicate hyperprolactinemia requiring treatment. 1, 2

Clinical Indications for Prolactin Testing

Prolactin testing is indicated in women presenting with:

• Menstrual abnormalities (oligomenorrhea or amenorrhea)
• Galactorrhea
• Infertility
• Sexual dysfunction
• Headaches with visual field defects (suggesting possible macroadenoma)
• Unexplained weight gain (reported in 23% of patients with macroprolactinomas) 2
• Low testosterone levels with low/normal LH in patients with symptoms of hypogonadism 2

Diagnostic Approach

• A single blood sample collected at any time of day is sufficient for prolactin measurement 2
• For mildly elevated levels (up to 5x upper limit of normal), consider serial measurements to exclude stress-induced elevation 1, 2
• Use age-specific and sex-specific reference ranges:
  • Non-pregnant females: 3.0-30.0 ng/mL
  • Postmenopausal females: 2.0-20.0 ng/mL 2

Additional Workup for Hyperprolactinemia

If prolactin is elevated, evaluate underlying causes:

1. Review medications (especially antipsychotics, which can cause hyperprolactinemia)
2. Check thyroid function (TSH, free T4) - hyperprolactinemia is common in hypothyroidism (43% of women) 2
3. Assess renal and liver function
4. Consider MRI with gadolinium for persistent unexplained hyperprolactinemia 3
5. Consider IGF-1 level to screen for acromegaly if clinically suspected 3

Treatment Considerations

If hyperprolactinemia is confirmed and a prolactinoma is diagnosed:

• Dopamine agonists are first-line treatment 2, 4
• Cabergoline is preferred due to better efficacy and tolerability 2, 5
• Treatment goals include normalizing prolactin levels, restoring gonadal function, reducing tumor size, preserving pituitary function, and preventing osteoporosis 2

Common Pitfalls to Avoid

1. Missing medication-induced hyperprolactinemia: Always review current medications, especially antipsychotics, before extensive workup
2. Overlooking hypothyroidism: Check thyroid function as primary hypothyroidism is a common cause of hyperprolactinemia
3. Ignoring the "high-dose hook effect": In patients with large pituitary lesions but only mildly elevated prolactin, consider serial dilutions of serum for accurate measurement 2
4. Unnecessary surgery: Most prolactinomas respond well to medical therapy; surgery should be reserved for specific cases like dopamine agonist resistance or intolerance 2, 6
5. Failure to monitor bone health: Untreated hyperprolactinemia can lead to bone density loss and increased fracture risk due to hypogonadism 2

While most cases of hyperprolactinemia follow a benign clinical course 7, proper diagnosis and management are essential to restore normal endocrine function and prevent long-term complications.