Hashimoto Thyreoiditis Is Associated with Defects of Cytochrome-c Oxidase in Oxyphil Askanazy Cells and with the Common Deletion (4,977) of Mitochondrial DNA

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Abstract
The activity of cytochrome-c oxidase, the terminal enzyme of the respiratory chain (complex IV), was studied at the ultra-structural level in a case of Hashimoto thyreoiditis. Cytochrome-c oxidase showed a heterogeneous reaction pattern in oxyphil cells, with scattered foci of oxyphil cells lacking cytochrome-c oxidase staining. In most of the cells the defect involved all the mitochondria, but there were also oxyphil cells with a heterogeneous mitochondrial population characterized by an intracellular coexistence of mitochondria with either intact cytochrome-c oxidase or lacking activity. Immunocyto-chemistry further disclosed loss of mitochondrially and nucle-arly encoded subunits of the enzyme. Molecular genetic analysis of mitochondrial DNA (mtDNA) revealed the presence of the 4977 base pair deletion (“common deletion”) of mtDNA (8,482–13,459) in the affected areas but not in normal thyroid tissue of the patient. The amount of deleted mtDNA varied between 2 and 8% of total mtDNA. The results demonstrate that oxyphil cell change in Hashimoto thyreoiditis is associated with functional and molecular genetic defects of the respiratory chain.