ALT

Liver enzyme - sensitive to hepatic fat (NAFLD) and the most common abnormality on routine panels.

What ALT Measures

ALT is a liver enzyme released into circulation when hepatocytes are damaged or stressed. The most common cause of elevated ALT is non-alcoholic fatty liver disease (NAFLD/MASLD) - affects ~25% of US adults. Less common but important causes include alcohol use, hepatitis (viral or autoimmune), medications, and acute liver injury.

The "normal" lab range (<55) masks meaningful clinical signal. Optimal ALT for metabolic health is <25 U/L. Sustained ALT 25–55 in a non-drinker usually means hepatic fat accumulation - actionable via weight loss, alcohol elimination, and metabolic intervention.

What Affects This Biomarker

ALT is influenced by: hepatic fat content (the primary driver), alcohol intake, body fat (visceral specifically), insulin resistance, viral hepatitis, medications (statins occasionally raise; high-dose acetaminophen; many supplements), and acute illness. GLP-1s reliably lower ALT via hepatic fat reduction; tesamorelin specifically reduces visceral and hepatic fat.

In the Context of Peptide Protocols

Track at baseline + every 3–6 months on any protocol. On GLP-1s expect 30–50% ALT reduction at maintenance dose - often the most reliable hepatic improvement signal. On HGH/tesamorelin protocols, watch for any rise (rare but possible). On peptide protocols generally, ALT shouldn't move much. Sustained elevation despite weight loss warrants hepatology workup.

Peptides That Commonly Move ALT

Conditions That Track ALT

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