Thyroid Cancer and Psoriasis: A Nested Case-Control Study.

Previous researchers have suggested an elevated risk of thyroid cancer (TC) in patients with psoriasis with mixed results. The current study evaluated the relationship of psoriasis with the risk of TC in an adult population. The data from the Korean National Health Insurance Service—Health Screening Cohort ≥ 40 years old were analyzed. In total, 6822 patients with TC were equalized with 27,288 control participants using overlap weighting adjustment based on the propensity score. The history of psoriasis was compared between the TC and control groups using multivariable logistic regression analysis. Secondary analyses were conducted according to age, sex, income, region of residence, systolic blood pressure, diastolic blood pressure, fasting blood glucose, total cholesterol, obesity, smoking, alcohol consumption, the Charlson Comorbidity Index scores, hypothyroidism, goiter, thyrotoxicosis, and thyroiditis. The history of psoriasis was not different in patients with TC (overlap-weighted odds ratio (OR) = 1.02, 95% confidence intervals (CI) = 0.85−1.22). The <55-year-old group showed a high rate of TC associated with psoriasis (overlap-weighted OR = 1.69, 95% CI = 1.22−2.36, p = 0.002). The population without hypothyroidism demonstrated an increased rate of TC related to psoriasis (overlap-weighted OR = 1.29, 95% CI = 1.06−1.57, p = 0.012). The patients with hypothyroidism showed a low rate of TC for psoriasis (overlap-weighted OR = 0.59, 95% CI = 0.37−0.96, p = 0.034). None of the other subgroups showed an association between psoriasis and TC. Psoriasis was not related to the risk of TC in the overall adult population. Young adults and populations without hypothyroidism indicated an elevated rate of TC for psoriasis.