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Gene & pathway reference · FROM DR. PURSER’S TEACHING

CTH

CTH helps make cysteine, one of the building blocks your body uses to make glutathione.

Based on teaching by Dan Purser, MD. How we prepare these guides

Updated Sep 23, 2026 · Educational reference

THE TEACHING CONNECTION

From homocysteine toward glutathione

From homocysteine toward glutathione

Dr. Purser places CTH in the sulfur-handling pathway that connects homocysteine with glutathione production. In that map, CTH concerns the downstream step that helps produce cysteine from cystathionine. Cysteine is one of the building blocks used to make glutathione.

Putting the pieces together

Cysteine or NAC supplies a building block; glutathione is the molecule made later in the pathway. If you are considering support, your symptoms and tolerance matter. A common CTH variant does not mean you must avoid sulfur foods or that more building blocks will help.

Where the VARS Triad and MTHFR Daily fit

If you are exploring homocysteine or cytokines, Dr. Purser may discuss MTHFR Daily and the VARS Triad: VARS Glutathione, VARS SOD, and VARS Catalase. He gives glutathione a central place in his approach to antioxidant support.

A gene result alone cannot tell you that you need these products or that they will treat a condition. Review your current results, medicines, goals, and tolerance with your clinician before choosing a product or dose.

Where this gene fits in transsulfuration

Dr. Purser places CTH on the route from homocysteine toward cysteine and glutathione-building chemistry. It distinguishes this downstream branch from recycling homocysteine back to methionine. That is why a homocysteine discussion can include both B-vitamin cofactors and antioxidant supply.

Some inherited disorders involve severe inherited enzyme disorders. A common SNP does not have the same meaning: having a listed variant does not establish an enzyme block, a sulfur intolerance or a need to restrict protein.

A question to bring to your visit

Are current nutrient/redox findings and my actual response to sulfur-containing products being considered alongside this result?

Reading your own results

Bring your original report, current results, health history, and medicines to your visit. This information can help you ask questions, but it cannot diagnose a condition or choose a supplement dose for you.

Variant lookup

These names can help you find an entry on your original genetic report. Seeing a name here does not tell you whether it affects your health or whether you need treatment.

rs1021737

Names you may see

Cystathionine Gamma-Lyase

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