Related Experiment Videos
Macroprolactin; high molecular mass forms of circulating prolactin
M N Fahie-Wilson1, R John, A R Ellis
1Department of Clinical Biochemistry, Southend Hospital, Westcliff-on-Sea, Essex SS0 0RY, UK. mfahie-wilson@southend.nhs.uk
Annals of Clinical Biochemistry
|June 14, 2005
Summary
Macroprolactin, a high molecular mass form of prolactin (PRL), can cause false hyperprolactinemia. Identifying macroprolactin is crucial to avoid misdiagnosis and unnecessary treatments, distinguishing it from bioactive monomeric PRL.
Area of Science:
- Endocrinology
- Clinical Chemistry
- Biochemistry
Background:
- Two high molecular mass prolactin (PRL) forms exist in serum: macroprolactin (>100 kDa) and big PRL (40-60 kDa).
- Macroprolactin is often a complex of PRL and IgG (150-170 kDa), formed post-pituitary secretion, with prolonged circulation and variable immunoassay reactivity.
- Macroprolactin can be the primary immunoreactive PRL form in some individuals, leading to apparent hyperprolactinemia.
Purpose of the Study:
- To investigate the nature and clinical significance of high molecular mass prolactin (PRL) forms in serum.
- To highlight the diagnostic challenges posed by macroprolactin and the need for accurate identification.
- To emphasize the importance of distinguishing macroprolactin from bioactive monomeric PRL.
Main Methods:
- Gel filtration chromatography (GFC) was used to identify and characterize high molecular mass PRL forms.
- Screening tests, particularly polyethylene glycol (PEG) precipitation, were employed for macroprolactin detection.
- GFC serves as a reference technique for confirming equivocal screening test results.
Main Results:
- Macroprolactin, though often lacking significant bioactivity, is a common cause of elevated total PRL levels in immunoassays.
- Macroprolactin is primarily confined to the intravascular space due to its large size.
- Big PRL is a consistent serum PRL component but rarely causes hyperprolactinemia.
Conclusions:
- Recognizing macroprolactin is essential to prevent diagnostic confusion and unnecessary patient treatment for apparent hyperprolactinemia.
- Laboratories should implement screening programs to detect macroprolactin in elevated total PRL samples.
- Further research is needed to fully understand the nature, relationships, and clinical implications of macroprolactin and big PRL.