Thyroid gland carcinoma (TGC), though only 1% of all carcinomas, is the most common endocrine neoplasm with an increasing incidence since the 1990s. Of the TGC types, papillary thyroid carcinoma (PTC) is the most common and has the best overall prognosis. Although primarily studied in various neural spectrum disorders, monoamine oxidase A (MAOA) may also contribute to cancer occurrence. This case control study assessed the prevalence of MAOA uVNTR polymorphism in PTC patients, compared its frequency with a healthy control, and assessed the variant’s impact on clinical features. The research participants consisted of 30 PTC patients (20 female, 10 male) over 18 years old who underwent thyroidectomy and radioiodine therapy at a Federal District private clinic and 30 paired and unrelated healthy volunteers (18 female, 12 male). The most frequent MAOA uVNTR alleles were 3R and 4R. Although no significant difference was detected in the genotypic distribution nor the PTC patients’ thyroglobulin, thyroid-stimulating hormone, and antithyroglobulin levels; body mass indexes; administered radiopharmaceutical (131I) doses; or biological sex, the presence of at least one 3R allele was associated with a larger tumor size (T3 + T4 staging). Thus, the 3R allele seems to be associated with PTC pathogenesis severity.
