Do TMPRSS6 variants increase hepcidin and raise risk of iron deficiency?

The regulation of systemic iron levels is heavily influenced by the TMPRSS6 gene, which encodes the protein matriptase-2. Research consistently demonstrates that common genetic variants in this gene act as a significant modifier of iron status and susceptibility to deficiency.

Clinical and effectiveness evidence

Large-scale genome-wide association studies (GWAS) and cohort analyses have robustly linked specific TMPRSS6 polymorphisms, such as rs855791 and rs4820268, to alterations in iron biomarkers.

• Biomarker impact: Variants like the G allele of rs4820268 are associated with a per-allele reduction of approximately 1% to 2% in transferrin saturation (TSAT) and 0.03 to 0.06 g/dL in hemoglobin levels.
• Anemia risk: In environments where dietary iron is scarce, the risk of iron deficiency (ID) or iron deficiency anemia (IDA) can be 2.6 to 6 times higher for individuals carrying these risk alleles compared to those with the protective genotypes.
• Clinical presentation: These genetic influences often manifest as microcytosis (smaller red blood cells) and an increased red cell distribution width (RDW), even before overt anemia develops.

Mechanistic explanations

The relationship between TMPRSS6 and iron status is governed by the hepcidin-ferroportin axis.

• Hepcidin regulation: Matriptase-2 normally serves as a "brake" on hepcidin production by cleaving membrane-bound hemojuvelin (HJV). This cleavage disrupts the BMP-SMAD signaling pathway that otherwise triggers hepcidin expression.
• Pathophysiology: Risk variants reduce the proteolytic activity or expression of matriptase-2. This leads to inappropriately elevated hepcidin levels, even when body iron stores are low.
• Iron restriction: Elevated hepcidin causes the degradation of ferroportin, the only known cellular iron exporter. This prevents iron absorption in the gut and traps existing iron within macrophages, effectively restricting the iron available for red blood cell production.

Bottom line

TMPRSS6 variants increase susceptibility to iron deficiency by impairing the body’s ability to suppress hepcidin. This genetic predisposition becomes clinically significant when iron intake is low or absorption is challenged, making these individuals more prone to iron-refractory deficiency patterns.