Pitfalls in the Diagnostic Evaluation of Hyperprolactinemia

Area of Science:

• Endocrinology
• Clinical Chemistry
• Reproductive Medicine

Background:

• Macroprolactinemia is the third most common cause of nonphysiological hyperprolactinemia.
• It can lead to hypogonadism, infertility, and galactorrhea in up to 40% of patients.
• Screening for macroprolactin is recommended for both symptomatic and asymptomatic individuals with elevated prolactin levels.

Purpose of the Study:

• To highlight the importance of diagnostic evaluation for hyperprolactinemia.
• To discuss the differential diagnosis of elevated prolactin levels.
• To emphasize the clinical utility of prolactin level magnitude in etiological determination.

Main Methods:

• Review of diagnostic criteria for hyperprolactinemia.
• Analysis of prolactin (PRL) level ranges in different etiologies.
• Consideration of the 'hook effect' in pituitary adenoma cases.

Main Results:

• Prolactin levels >250 ng/mL suggest prolactinomas but can occur in macroprolactinemia, drug-induced hyperprolactinemia, or renal failure.
• Most patients with nonfunctioning pituitary adenomas (NFPAs), drug-induced hyperprolactinemia, macroprolactinemia, or systemic diseases have PRL levels <100 ng/mL.
• The 'hook effect' can cause falsely low PRL levels in large pituitary adenomas and can be identified by diluting serum samples.

Conclusions:

• Appropriate diagnostic evaluation is essential for effective treatment of hyperprolactinemia.
• Ruling out pregnancy, drug effects, hypothyroidism, and renal failure is critical before macroprolactin screening.
• Understanding prolactin level patterns and potential interferences like the hook effect aids in accurate diagnosis.