From the Guidelines
For patients with elevated prolactin levels, I strongly recommend ordering a comprehensive set of laboratory tests including TSH, free T4, comprehensive metabolic panel (CMP), pregnancy test (in women of childbearing age), and MRI of the pituitary with contrast to identify the underlying cause of hyperprolactinemia. These tests are crucial as they help detect hypothyroidism, evaluate kidney and liver function, and identify prolactinomas or other sellar masses that could be causing the elevated prolactin levels 1.
Key Laboratory Tests
- TSH and free T4 to detect hypothyroidism, which can cause secondary prolactin elevation
- Comprehensive metabolic panel (CMP) to evaluate kidney and liver function, as renal failure and cirrhosis can increase prolactin levels
- Pregnancy test in women of childbearing age, as pregnancy naturally elevates prolactin
- MRI of the pituitary with contrast to identify prolactinomas or other sellar masses
Additional Considerations
- Medication review is important as many drugs (antipsychotics, metoclopramide, verapamil, estrogens) can cause hyperprolactinemia 1
- Consider repeating prolactin measurement to confirm elevation, ideally in the morning after fasting and avoiding breast stimulation
- If clinical suspicion warrants, check for macroprolactin by polyethylene glycol precipitation to identify biologically inactive forms that can cause falsely elevated readings without clinical significance 1
Importance of Age-Specific and Sex-Specific Reference Ranges
It is also important to use age-specific and sex-specific prolactin reference ranges, as serum prolactin concentrations vary with age and sex 1. This ensures accurate interpretation of prolactin levels and helps in identifying the underlying cause of hyperprolactinemia.
Exclusion of Confounding Conditions
Exclusion of confounding conditions such as hypothyroidism, renal and/or hepatic impairment, and use of medications that cause hyperprolactinemia is crucial for an accurate diagnosis 1. By following these recommendations, clinicians can ensure that patients with elevated prolactin levels receive appropriate diagnosis and management, ultimately improving their morbidity, mortality, and quality of life.
From the Research
Laboratory Tests for Hyperprolactinemia
- A serum prolactin (PRL) level is obtained in response to a specific clinical presentation, including symptoms of hyperprolactinemia 2
- An initial level above the normal range should be followed by a repeat level from a blood sample drawn in the morning with the patient in a fasting state 2
- The medical history and a few laboratory tests can eliminate the most common physiologic and pharmacologic causes of hyperprolactinemia, including pregnancy, primary hypothyroidism and treatment with drugs (such as neuroleptics) that reduce dopaminergic effects on the pituitary 2
Diagnostic Evaluation
- Radiologic imaging of the sella turcica is necessary to establish whether a PRL-secreting pituitary adenoma or other lesion is present 2
- Patients with unexplained elevations of serum prolactin or with a level above 200 ng/mL should undergo imaging of the sella turcica 3
- Analytical issues (presence of macroprolactin or of the hook effect) need to be taken into account when interpreting the prolactin values 4