Genetically predicted selenium concentrations and thyroid function: A two‐sample Mendelian randomization study

Summary

This two-sample Mendelian randomization study used genetic instruments from genome-wide association studies to examine causal relationships between selenium concentrations and thyroid function, minimising bias from confounding and reverse causation. Genetically determined toenail and blood selenium concentrations showed a significant negative association with FT4 levels and a suggestive protective association with hypothyroidism risk, with effects more pronounced in women. No significant causal effects were detected on TSH levels or hyperthyroidism risk.

Regional applicability

This is an international study using GWAS data from multiple populations; findings are applicable to understanding selenium's causal role in thyroid function across populations with similar genetic architecture. UK clinical practitioners should consider these causal estimates alongside existing dietary selenium guidance when evaluating thyroid health in their patient populations.

Key measures

Genetically predicted selenium concentrations (toenail and blood, blood only); thyroid-stimulating hormone (TSH), free thyroxin (FT4), hypothyroidism risk, hyperthyroidism risk

Outcomes reported

The study examined causal associations between genetically predicted selenium concentrations and thyroid phenotypes (TSH, FT4, hypothyroidism, hyperthyroidism) using Mendelian randomization. Genetically determined toenail and blood selenium was negatively associated with free thyroxin (FT4) and suggestively associated with reduced hypothyroidism risk.

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