How does my DNA influence DIO1 activity?

The DIO2 thyroid-conversion enzyme that turns inactive T4 into active T3. The COMT and CYP1A1 enzymes that move estrogen through Phase I detox. The SHBG variants that bind or release testosterone. The CYP17A1 and HSD3B2 nodes in the steroid synthesis cascade. Your "normal" labs may sit on top of a genome that needs a different intervention.

What kind of test do I need to see my DIO1 Activity result?

Whole-genome sequencing at 30× clinical depth. Consumer SNP-chip tests like 23andMe or AncestryDNA only read ~0.02% of your DNA and miss most of the variants this analysis needs. Mosaic reads all 3 billion base pairs and produces the full report, all 108 insights.

How is DIO1 Activity different from clinical lab testing?

Clinical labs measure downstream biomarkers (blood levels, hormone values, metabolic byproducts) at a single point in time. Genomic insights like DIO1 Activity reveal the underlying variant that shapes the biology, which is constant for life. The two are complementary: labs show the current snapshot; genomics shows the long-term tendency and where lifestyle leverage is highest.

DIO1 Activity

One of 108 insights in your Genomic Lifestyle Optimization Report.

DIO1 handles the body-wide conversion of inactive T4 into active T3. Reduced activity is a common reason for persistent hypothyroid symptoms (fatigue, weight gain, cold intolerance) even when TSH looks "normal." Standard testing misses this entirely.

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How your DNA shapes DIO1 activity.

DIO1 (deiodinase 1) is one of the three enzymes that activate thyroid hormone, converting T4 (the storage form) into T3 (the active form). DIO1 acts primarily in the liver and contributes to the circulating pool of T3; DIO2 (a Phase 1 exemplar) acts in tissues. Together they decide how much active thyroid hormone reaches the cells that need it.

Carriers of common DIO1 reduced-activity variants are associated with lower hepatic T3 production and reduced circulating T3 levels, even when T4 and TSH look adequate. Carriers of DIO2 reduced-activity variants compound the picture at the tissue level. The combined effect can produce the symptom pattern of clinical hypothyroidism even with "normal" thyroid labs.

Selenium is the required cofactor for both DIO1 and DIO2. Brazil nuts, seafood, and selenium-rich foods support both enzymes. Iodine status shapes upstream T4 availability. Zinc and iron each influence the broader thyroid network. Chronic stress, severe caloric restriction, and certain medications (lithium, amiodarone) all suppress deiodinase activity.

The "labs look normal but I feel hypothyroid" pattern is much more common than the standard workup suggests. Which DIO1/DIO2 combination you carry decides whether the conversation with a clinician needs to include free T3 testing, and whether selenium and supporting cofactors are the variable that actually shifts how you feel.

In your report, DIO1 Activity is one dark card: a color marker set by your variants, the mechanism in plain language, and one practical next step.

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Thyroid: the 4-insight cluster.

DIO1 Activity is one finding in a tightly related cluster. Mosaic reads the other 3 alongside it, so you see the whole biology, not an isolated data point.

About DIO1 Activity.

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This is one of 108. Your report reads all of them, from one cheek swab.

See the real pages first. Then order your kit and the full Lifestyle Report lands in 15 to 20 days.

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