Can low vitamin D status and CYP2R1 rs10741657 AG affect autoimmune thyroid antibody activity?

Low systemic vitamin D status, compounded by genetic variations in its metabolic pathways, plays an important role in immune function and autoimmunity.

Genetic and physiological mechanisms

• The CYP2R1 gene encodes the principal hepatic 25-hydroxylase enzyme responsible for converting dietary and synthesized vitamin D into its primary circulating form, 25-hydroxyvitamin D [25(OH)D].
• The rs10741657 AG genotype, which carries the risk-associated G-allele, is robustly linked to decreased CYP2R1 expression and reduced hepatic 25-hydroxylase activity.
• This genetic impairment, combined with a low baseline vitamin D status, directly restricts the systemic 25(OH)D pool available for downstream metabolic and immune pathways.

Immune tolerance and thyroid autoimmunity

• Active 1,25(OH)2D is a potent immunomodulator that maintains immune tolerance by regulating dendritic cells, promoting T-regulatory (Treg) cell differentiation, and modulating the inflammatory Th1/Th17 cytokine axis.
• Reduced circulating 25(OH)D levels limit the capacity of local immune cells to synthesize active 1,25(OH)2D via intracrine pathways, compromising immune tolerance and creating a pro-inflammatory state.
• While epidemiological evidence consistently connects vitamin D deficiency to autoimmune thyroid diseases, direct clinical evidence mapping the CYP2R1 rs10741657 AG genotype specifically to quantitative thyroid peroxidase (TPO) or thyroglobulin (Tg) antibody levels remains limited. However, an indirect pathway linking genetically reduced vitamin D availability to altered immune tolerance and elevated thyroid autoantibody activity is highly plausible.

Bottom line

• Bottom line: The CYP2R1 rs10741657 AG genotype and low baseline vitamin D status directly impair hepatic 25-hydroxylase activity, leading to lower circulating 25(OH)D. This deficit compromises local immune tolerance mechanisms, which plausibly influences autoimmune thyroid antibody activity, though direct quantitative genetic-correlation data are still emerging.