Genetic predisposition to hypothyroidism

Why it matters

The thyroid gland produces predominantly T4, while a significant proportion of active T3 is formed outside the thyroid. This conversion is carried out by specialised enzymes called deiodinases. Their activity affects the availability of thyroid hormones in the bloodstream and individual tissues. Deiodinase activity is partly influenced by genetic factors. Certain variants in DIO1 and DIO2 have been associated with differences in thyroid hormone metabolism, although the magnitude and clinical significance of these effects may vary.

The test provides the physician with additional information about inherited differences in thyroid hormone conversion. Results are interpreted alongside TSH, free T4, clinical symptoms, medical history, and other diagnostic findings.

Genetic assessment of thyroid function

Hypothyroidism develops when the effects of thyroid hormones in the body are insufficient. Diagnosis is based primarily on laboratory assessment of thyroid function. One of the key markers is TSH, which is usually assessed together with free T4. When hypothyroidism symptoms are present, the physician interprets laboratory findings alongside the patient’s symptoms, medical history, and other clinical information.

A genetic analysis for hypothyroidism provides additional information about inherited characteristics of thyroid hormone metabolism. A genetic test for hypothyroidism examines variants in DIO1 and DIO2, genes associated with deiodinase function and the conversion of T4 into active T3. The results complement the clinical picture and are interpreted alongside standard thyroid function markers.

Genetic characteristics of thyroid hormone metabolism

Conversion of thyroxine T4 into active T3

Gene variants associated with deiodinase function

Individual characteristics of T3 availability in tissues

Additional information for a comprehensive assessment of thyroid status

Family history of thyroid disorders

Reduced thyroid function

Diagnosed hypothyroidism

Changes in TSH and thyroid hormone levels

Additional assessment when selecting or adjusting treatment

Persistent symptoms during thyroid hormone replacement therapy

Pregnancy planning and thyroid function monitoring

Assessment of thyroid status during adolescence

Monitoring thyroid function in older adults

Conditions that may affect thyroid hormone metabolism

Extended assessment of individual thyroid hormone metabolism

Programme components

The panel includes analysis of DIO1 and DIO2. Both genes are associated with enzymes involved in thyroid hormone metabolism, although their physiological roles differ. DIO1 contributes to peripheral thyroid hormone metabolism, while DIO2 plays a particularly important role in the local production of active T3 within tissues.

Genetic variants are determined once and remain unchanged throughout life. The results are considered as an additional part of the overall clinical picture.

DIO1 gene

DIO1 is associated with type 1 deiodinase, an enzyme involved in thyroid hormone metabolism, including the activation and inactivation of different forms of thyroid hormones.
The panel includes: 3 DIO1 polymorphisms. Their analysis provides additional information about inherited characteristics of peripheral thyroid hormone metabolism and the production of circulating T3. Certain DIO1 variants have been associated with differences in thyroid hormone levels and ratios, although the magnitude of these effects may be small.

DIO2 gene

DIO2 is associated with type 2 deiodinase. This enzyme converts T4 into active T3 directly within tissues and therefore contributes to the local regulation of thyroid hormone action. D2 is particularly relevant to the central nervous system and pituitary-thyroid regulation.
The test includes: 2 DIO2 polymorphisms and identifies genetic variants that may influence local T3 production. The possible association of certain DIO2 variants with patient well-being and response to thyroid hormone replacement therapy continues to be studied. Current evidence is insufficient to select treatment based solely on the results of this genetic test.

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Genetic predisposition to hypothyroidism