This test detects autoantibodies against selenoprotein P in serum, which interfere with the normal transport and cellular utilization of selenium. Selenoprotein P (SelP) is the main selenium transporter from the liver to peripheral tissues via specific receptors. The presence of autoantibodies may prevent Selenoprotein P from binding to these receptors, resulting in reduced cellular selenium uptake, even when total serum selenium levels appear normal.
This analysis is primarily recommended in cases of unexpectedly poor response to selenium supplementation, suspected functional selenium deficiency, or persistent symptoms such as fatigue, despite adequate dietary intake and normal serum levels of both selenium and selenoprotein P.
The method is based on specialized immunoenzymatic assays that detect IgG autoantibodies against selenoprotein P in serum. Although this is a specialized test, it contributes significantly to a more comprehensive assessment of selenium bioavailability, particularly in cases where symptoms appear disproportionate to standard biochemical findings.
Interpretation
The presence of autoantibodies against selenoprotein P is considered an indicator of immunological interference with its normal function. Specifically, these autoantibodies may block the interaction between Selenoprotein P and its cellular receptors, preventing selenium from reaching target tissues. This may lead to a functional selenium deficiency, even when total serum selenium and selenoprotein P levels appear within normal ranges.
A positive SELENOP-aAb result is not diagnostic of an autoimmune disease but rather serves as supportive laboratory evidence of impaired cellular selenium utilization. This finding becomes particularly relevant in cases where:
- Free T3 is low
- Fatigue or mitochondrial dysfunction persists
- The clinical response to selenium supplementation is suboptimal
Interpretation should always be based on the overall clinical context and take into account the patient’s symptom profile, comorbidities, and results of other relevant functional markers such as selenoprotein P, free T3, or inflammation indicators.
Diagnostic Value of the Test
The detection of autoantibodies against selenoprotein P is a specialized tool for assessing the body's ability to utilize selenium effectively. This test is particularly useful when clinical symptoms or biochemical findings are not fully explained by total selenium levels or SelP concentration. In such contexts, the presence of autoantibodies against selenoprotein P may reveal a hidden mechanism of impaired selenium transport and uptake that is not detectable by standard testing. It is especially relevant in the following clinical scenarios:
- Thyroid dysfunction with normal hormone levels. In patients with chronic fatigue, suspected hypothyroidism, or impaired T4-to-T3 conversion, despite normal TSH or T4, autoantibodies against selenoprotein P may indicate a local selenium deficit in the thyroid, due to disrupted SelP-mediated delivery. The test aids in the differential diagnosis of thyroid dysfunction in the presence of normal laboratory values.
- Poor response to selenium therapy. When selenium supplementation fails to deliver expected benefits, this test may show that selenium is not reaching target tissues effectively. Especially in individuals with normal selenoprotein P levels but persistent functional symptoms, the presence of autoantibodies against the protein enables a more accurate assessment of selenium status.
- Chronic fatigue and low T3 profile. In patients with low energy availability, mental sluggishness, reduced mitochondrial performance, or low free T3, the presence of autoantibodies against Selenoprotein P may explain the disconnect between selenium intake and its intracellular utilization. The test also supports a broader metabolic and energy profiling.
- Immune dysregulation and hormone-sensitive cancers. Preliminary research has linked autoantibodies against selenoprotein P to worse prognosis in patients with breast cancer, suggesting a potential role in limiting antioxidant defense. In the setting of inflammation or autoimmunity, the test may additionally contribute to a more complete immunometabolic evaluation of the patient.
The test is recommended as a complementary diagnostic tool to be used alongside the measurement of selenoprotein P, free T3, and other functional markers and should not be interpreted in isolation.
A negative result has value for exclusion purposes, though it does not rule out other causes of impaired selenium uptake or utilization. Conversely, a positive finding strengthens the suspicion of immunological interference in a critical metabolic pathway and may explain why selenium is not "working," even though it is "present." Thus, this test does not replace selenium or selenoprotein P measurements but rather complements them, especially in complex or unexplained cases.
Therapeutic Approaches
Therapeutic strategies for positive autoantibody detection against selenoprotein P focus on understanding and addressing the functional disruption of selenium transport, which may lead to intracellular selenium deficiency even when dietary intake appears sufficient.
This test serves as a clinical guidance tool for personalized interventions, particularly within the context of functional and preventive medicine. In collaboration with the treating physician, the findings may support decisions such as adjusting the selenium supplementation strategy (e.g., dose, form, timing), supporting thyroid and energy metabolism, or monitoring treatment response in conditions such as chronic fatigue, thyroid disorders, or chronic inflammation.
Last updated: 20/1/2026
