DIO2 rs225014: Understanding the Thr92Ala Variant
The rs225014 variant is a common genetic change in the DIO2 gene that results in a threonine-to-alanine substitution at position 92. This polymorphism is frequently studied for its potential influence on how the body activates thyroid hormones and its possible associations with various metabolic and physiological traits.
What each genotype means
Typical DIO2 enzyme function
You carry two copies of the reference T allele, which encodes the ancestral threonine (Thr) at position 92 of the type 2 deiodinase enzyme. Research suggests this genotype provides baseline intracellular conversion of thyroxine (T4) to active triiodothyronine (T3) in tissues such as skeletal muscle and the central nervous system. Clinical associations with altered metabolic rate or endurance remain limited and inconsistent across broader population studies.
Found in roughly 35% to 45% of individuals of European ancestry and more than 70% of individuals of East Asian ancestry.
Intermediate DIO2 enzyme function
You carry one copy of the C allele, which encodes alanine (Ala) instead of threonine at codon 92 of the DIO2 enzyme. Published studies report mixed evidence regarding whether a single copy subtly influences local intracellular T4-to-T3 thyroid hormone conversion or baseline metabolic phenotypes. If you are taking thyroid hormone replacement therapy such as levothyroxine, any questions regarding your symptom response or medication dosing should be discussed directly with your clinician or pharmacist.
Carried by approximately 45% to 50% of European-ancestry populations and roughly 25% of East Asian populations.
Altered DIO2 enzyme activity
You carry two copies of the C allele (homozygous Ala92), which has been linked in some research to reduced intracellular type 2 deiodinase activity and altered local tissue T3 generation. Clinical evidence regarding effects on baseline metabolic rate, muscle performance, or psychological symptoms remains limited and variable between cohorts. If you receive thyroid hormone therapy and experience persistent symptoms despite normal standard lab values, consult your healthcare provider or pharmacist before considering any regimen adjustments.
Present in approximately 12% to 16% of individuals of European ancestry and fewer than 5% of individuals of East Asian ancestry.
What is the rs225014 Variant?
The rs225014 variant is a single-nucleotide polymorphism (SNP) located within the DIO2 gene. In this specific genetic change, a threonine amino acid is replaced by an alanine at position 92 of the protein, which is why it is often referred to as the Thr92Ala polymorphism. This variant is located on the DIO2 gene, which provides instructions for making the type 2 deiodinase enzyme. This enzyme is responsible for converting the inactive thyroid hormone, thyroxine (T4), into the active form, triiodothyronine (T3), within specific tissues. Because this conversion is essential for regulating cellular metabolism and energy expenditure, researchers have long investigated whether this structural change in the enzyme affects its efficiency or stability, potentially altering how different tissues respond to thyroid hormone signals.
The Role of the DIO2 Gene
The DIO2 gene encodes the type 2 deiodinase enzyme, which plays a critical role in the body's endocrine system. Unlike other deiodinases that act primarily in the liver or kidneys, type 2 deiodinase is highly expressed in tissues such as the brain, skeletal muscle, and brown adipose tissue. By converting T4 to T3 locally, this enzyme allows these tissues to maintain appropriate levels of active thyroid hormone, which is vital for processes like thermogenesis, glucose metabolism, and neurological function. Because the enzyme acts as a local regulator, it helps the body fine-tune its response to thyroid hormone independently of the levels circulating in the bloodstream. When the Thr92Ala variant is present, some studies suggest it may lead to reduced enzyme activity or altered expression, prompting researchers to explore if this contributes to localized differences in how tissues manage energy and metabolic health.
Research Associations and Evidence Strength
Scientific research into rs225014 has produced mixed and often conflicting results. Over the years, the variant has been investigated for associations with a wide range of conditions, including type 2 diabetes, insulin resistance, obesity, and even osteoarthritis. Some studies have reported that individuals with the Ala/Ala genotype might show subtle differences in glucose disposal or insulin sensitivity. However, other large-scale studies, such as those involving thousands of participants, have failed to find a consistent, statistically significant link between this variant and these metabolic diseases after correcting for multiple testing. The current consensus in the endocrinology community is that the evidence for a direct, causative role of rs225014 in these common metabolic disorders remains limited. Because of the heterogeneity in study designs, sample sizes, and ethnic backgrounds, it is difficult to draw definitive conclusions about the clinical impact of this variant on an individual's health.
Understanding Your Genetic Information
If you have received information about your rs225014 genotype, it is important to view it within the context of current scientific uncertainty. Genetic variants like this are rarely the sole cause of complex metabolic traits, which are typically influenced by a combination of many genes, lifestyle factors, diet, and environment. Because the scientific community has not reached a consensus on the clinical significance of this variant, it is not currently used as a diagnostic tool for thyroid disorders or metabolic conditions. You should never use this information to make changes to your medical care, such as adjusting thyroid medication or dietary habits, without consulting a qualified healthcare professional. If you have concerns about your thyroid function or metabolic health, speak with your doctor, who can order validated clinical tests to assess your actual hormone levels and overall health status.
How common is this variant?
The minor allele (G) frequency varies significantly by ancestry, appearing in approximately 35–40% of European populations and roughly 15% of East Asian populations.
Frequently asked questions
Does the rs225014 variant cause thyroid disease?
No, the rs225014 variant is not considered a direct cause of thyroid disease. While it is involved in the conversion of thyroid hormones, current research has not established it as a diagnostic marker for clinical thyroid conditions.
Should I change my diet based on my DIO2 genotype?
No. There is no scientific evidence to support changing your diet based on this specific genetic variant. Metabolic health is complex and should be managed through evidence-based guidance from a doctor or registered dietitian.
Is the rs225014 variant linked to weight gain?
Some studies have explored a potential link between this variant and body mass index or metabolic traits, but results have been inconsistent. Large-scale studies have often failed to find a significant association, meaning it is not a reliable predictor of weight.
Can I use this result to adjust my thyroid medication?
Absolutely not. You must never adjust your medication based on genetic test results. Always consult your endocrinologist or primary care physician before making any changes to your prescribed treatment plan.
Sources & further reading
Educational information only, last refreshed 10/19/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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