In one sentence
Seven numbers about the liver: four enzymes that leak into the blood when liver cells or the bile ducts are stressed (ALT, AST, GGT, ALP), the pigment the liver clears from old red cells (bilirubin), and the two protein figures that say what it is making (albumin and total protein).
Why it matters
The liver is where fat, sugar and alcohol are handled, so for a well adult the panel is mostly a metabolic reading. ALT is the enzyme most specific to liver cells, and its reference range has been argued over: in 6,835 first-time blood donors in Milan with no sign of liver disease, ALT rose with body mass index and with the markers of disturbed fat and sugar metabolism, and once the people with those were set aside the healthy upper limits were 30 U/L for men and 19 for women, well below the 40 and 30 the laboratory used (Prati 2002). GGT rises with alcohol, with fat in the liver and with the medicines the liver processes, and it carried a signal of its own: in 163,944 Austrian adults followed for up to 17 years, cardiovascular mortality rose with GGT in a dose-dependent way, with a hazard ratio of about 1.65 per unit of log GGT in both sexes and a steeper relation under the age of 60 (Ruttmann 2005). AST is less specific, because muscle and red cells contain it too, and the ratio of the two enzymes (the De Ritis ratio) is read in its own entry. Albumin is the liver's main product and falls with inflammation, poor nutrition and illness, which is why it is one of the nine PhenoAge inputs; alkaline phosphatase, which comes from bone as well as from the bile ducts, is another.
What moves it
Upward: fat in the liver, which tracks waist and insulin resistance; alcohol, which raises GGT first and most; weight gain; a number of medicines and supplements, from paracetamol at high dose to some herbal extracts; a viral illness; and muscle. Hard muscular work raises ALT and AST for a week or more: in fifteen healthy men used to moderate exercise, an hour of weightlifting raised AST, ALT, creatine kinase and myoglobin for at least seven days, while bilirubin, GGT and ALP stayed within their ranges (Pettersson 2007). Bilirubin rises with fasting and illness in people with a common, harmless inherited variation in its handling, and with the breakdown of red cells. Albumin falls with inflammation and rises with dehydration. Downward over months: weight loss, less alcohol, more movement.
How to measure it well
A fasting morning draw on the panel's day. No hard training for 48 hours (the enzymes stay up for days after a heavy session, so a draw after one reads as a liver finding that is a muscle finding), no alcohol for 48 hours, and no draw within two weeks of a viral illness. Record every supplement and medicine in VT, because the panel is read against them. Same laboratory each time.
How Vitality Tracker uses it
Each analyte is stored as reported with the laboratory's range and flag, which VT shows and never overrides. From one draw the panel feeds FIB-4 (AST and ALT, with platelets and age), the hepatic steatosis index (the ALT-to-AST ratio with BMI), the De Ritis ratio, PhenoAge (albumin and alkaline phosphatase) and, where calcium is bundled, corrected calcium. Typical laboratory reference, then VT's working optimal (v0.1), marked working until the clinical advisor has reviewed it: ALT < 45 U/L · < 30 men, < 25 women (the Milan study's healthy limits were 30 and 19; the women's working value is the advisor's to settle); AST < 40 · < 30; GGT < 60 · < 30; albumin 35 to 50 g/L · ≥ 40; bilirubin, alkaline phosphatase and total protein carry the laboratory's range alone. When the Supplement Tracker holds creatine, the kidney entry's note applies beside creatinine, not here; when a keto plan is active, the lipid entry's note applies. Re-test yearly, or at six months when a supplement, a medicine or heavy training is new, and whenever something hepatically active is started.
How far to trust the number
Laboratory: enzyme assays are precise, but the enzymes answer to last week as much as to the liver, so the pre-draw rules matter more here than for most tests. Two laboratories can differ in whether the assay is supplemented with pyridoxal phosphate, which shifts the transaminases a little, one more reason to use the same laboratory.
Sources
- Prati D, et al. Updated definitions of healthy ranges for serum alanine aminotransferase levels. Ann Intern Med 2002;137:1–10. doi:10.7326/0003-4819-137-1-200207020-00006
- Ruttmann E, et al. Gamma-glutamyltransferase as a risk factor for cardiovascular disease mortality: an epidemiological investigation in a cohort of 163,944 Austrian adults. Circulation 2005;112:2130–7. doi:10.1161/CIRCULATIONAHA.105.552547
- Pettersson J, et al. Muscular exercise can cause highly pathological liver function tests in healthy men. Br J Clin Pharmacol 2008;65:253–9. doi:10.1111/j.1365-2125.2007.03001.x
- Botros M, Sikaris KA. The De Ritis ratio: the test of time. Clin Biochem Rev 2013;34:117–30. PMID 24353357
- Vitality Tracker, Recommended baseline lab panel v0.1; optimal set v0.1 (working).