Can GSTP1 rs1695 AG, low CoQ10, and high ferritin impair thyroid function?

In individuals presenting with compromised antioxidant systems and altered genetic detoxification pathways, thyroid hormone regulation and tissue integrity are frequently compromised.

Genetic and biomarker interactions

• GSTP1 rs1695 AG genotype: This heterozygous variant produces an isoleucine-to-valine substitution (Ile105Val) at the substrate-binding H-site, resulting in a moderately reduced, intermediate-metabolizer phenotype. In cytosolic assays using 1-chloro-2,4-dinitrobenzene (CDNB), conjugation activity is intermediate (~62 nmol/mg/min) compared to the wild-type AA (~75 nmol/mg/min) and homozygous GG (~52 nmol/mg/min) genotypes. Under systemic challenge, this partially reduced capacity limits the clearance of reactive electrophiles and lipid peroxidation products.
• Low CoQ10 and high ferritin: High ferritin levels serve as an acute-phase inflammatory reactant while promoting iron-mediated reactive oxygen species (ROS) generation via the Fenton reaction. Concurrently, depleted levels of CoQ10 (ubiquinol) indicate a failing lipid-soluble antioxidant buffer, leading to unmitigated cellular oxidative-inflammatory stress.

Downstream mechanistic pathways

• Deiodinase enzyme dysregulation: Systemic oxidative-inflammatory stress and elevated cytokines (such as IL-6) directly inhibit type 1 (DIO1) and type 2 (DIO2) iodothyronine deiodinases, which are responsible for activating thyroxine (T4) into active triiodothyronine (T3).
• Hormone inactivation: Simultaneously, this stress environment upregulates type 3 deiodinase (DIO3), shifting thyroid hormone metabolism toward inactivation and generating elevated levels of reverse T3 (rT3). Additionally, because proper iron handling is essential for deiodinase and thyroid peroxidase function, dysregulated iron storage further impairs thyroid tissue integrity and downstream signaling.

Bottom line

• The GSTP1 rs1695 AG genotype reduces baseline detoxification efficiency, which—when paired with high ferritin and low CoQ10—promotes systemic oxidative-inflammatory stress that directly impairs thyroid function by suppressing DIO1/DIO2, upregulating DIO3, and causing a low-T3/high-rT3 signaling state.