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Macroprolactin: what is it and what is its importance?
1Department of Chemical Pathology, Guy's and St Thomas' NHS Trust, London, UK. hazim.sadideen@kcl.ac.uk
International Journal of Clinical Practice
|April 20, 2006
Summary
Macroprolactin, a large form of prolactin (PRL), can cause elevated PRL levels without underlying pathology. Screening for macroprolactin is crucial to avoid unnecessary investigations for hyperprolactinaemia.
Area of Science:
- Endocrinology
- Clinical Chemistry
Background:
- Monomeric prolactin (PRL) is the predominant form in serum (95%), with molecular weight of 23 kDa.
- Macroprolactin, an antigen-antibody complex (>100 kDa), constitutes <1% of circulating PRL but can cause hyperprolactinaemia.
Purpose of the Study:
- To highlight the clinical significance of macroprolactin as a cause of hyperprolactinaemia.
- To emphasize the importance of screening for macroprolactin to prevent unnecessary diagnostic workups.
Main Methods:
- Review of existing literature on prolactin isoforms and hyperprolactinaemia.
- Discussion of diagnostic methods including polyethyleneglycol precipitation and gel filtration chromatography.
Main Results:
- Hyperprolactinaemia is typically due to monomeric PRL (e.g., prolactinoma, pituitary stalk compression).
- Macroprolactinaemia can be a cause of elevated PRL levels, sometimes without associated pathology.
- Clinical presentation or imaging may be inconsistent with PRL levels, suggesting macroprolactin.
Conclusions:
- Macroprolactinaemia should be considered in the differential diagnosis of hyperprolactinaemia, especially when clinical findings contradict PRL levels.
- Screening for macroprolactin using methods like polyethyleneglycol precipitation can prevent unnecessary investigations.
- Gel filtration chromatography remains the gold standard for macroprolactin confirmation.