# Alkaline phosphatase (ALP)

Alkaline phosphatase (ALP) is an enzyme that snips phosphate groups in an alkaline environment. The level in your blood is a mix of forms from several organs, mainly your liver, bone, intestine, and (in pregnancy) placenta. A high ALP most often means liver or bile-duct trouble (especially cholestasis) or fast bone turnover (as in Paget's disease, bone metastases, or overactive parathyroid). How do you tell liver from bone? If GGT (or 5'-nucleotidase) is up alongside ALP, the source is the liver, since bone-building cells do not make those. A low ALP can point to a rare condition (hypophosphatasia), zinc or magnesium deficiency, or low thyroid. In longevity terms, a persistently high ALP has been tied to higher death from all causes and from heart disease, even apart from liver disease.

## Sources

- Wannamethee SG, Sattar N, Papcosta O, Lennon L, Whincup PH. (2013). Alkaline phosphatase, serum phosphate, and incident cardiovascular disease and total mortality in older men. Arteriosclerosis, Thrombosis, and Vascular Biology. https://doi.org/10.1161/ATVBAHA.112.300826

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