GCT-ALP (germ cell tumour alkaline phosphatase), also known as placental-like ALP or Regan isoenzyme, is a specific isoenzyme of alkaline phosphatase that is normally expressed by placental tissue during pregnancy and by certain germ cell tumours. In non-pregnant individuals, its presence in the blood is strongly associated with malignancy.
GCT-ALP is elevated in a range of germ cell tumours including some testicular and ovarian germ cell cancers, and is also found in other malignancies including lung and gynaecological cancers. As part of the ALP isoenzyme profile, GCT-ALP helps identify the tumour source of an elevated total ALP result and provides diagnostic information in the investigation and monitoring of germ cell malignancies.
FAQs
What is the Regan isoenzyme?
The Regan isoenzyme is an alternative name for the placental-like form of alkaline phosphatase (GCT-ALP). It was named after the patient in whom it was first identified. It is normally produced by placental tissue in pregnancy but when found in non-pregnant individuals, it is a tumour marker associated with germ cell and other cancers.
Which cancers produce GCT-ALP?
GCT-ALP can be produced by germ cell tumours (testicular and ovarian), some lung cancers, gynaecological malignancies, and other solid tumours. It is part of a broader panel of tumour markers rather than a standalone cancer-specific test.
Is GCT-ALP part of a standard blood test?
No. GCT-ALP is part of ALP isoenzyme analysis, which is ordered specifically when total ALP is elevated and the source needs to be identified, or in the investigation and monitoring of known or suspected germ cell tumours.
Can smoking raise GCT-ALP?
Some studies have found a weak association between smoking and mildly elevated GCT-ALP, possibly reflecting subclinical lung tissue changes. However, any detectable GCT-ALP should still be clinically evaluated rather than attributed to smoking without investigation.
