Higher prevalence of thyroid dysfunction in patients with erythrodermic psoriasis

The association of psoriasis with thyroid dysfunction has been investigated. However, it remains unclear; some papers indicate it, and others do not. In this study, we evaluate the prevalence of thyroid dysfunction in patients with psoriasis vulgaris (PsV), psoriatic arthritis (PsA), generalized pustular psoriasis (GPP) and erythrodermic psoriasis (EP), and the association of thyroid dysfunction with inflammation. Data on 201 psoriatic patients visiting our hospital from January 2014 to November 2017 (159 men and 42 women; 74 PsV, 42 PsA, 38 GPP and 47 EP) were retrospectively analyzed. Thirty-three percent of psoriatic patients had thyroid dysfunction. The percentage of patients with thyroid dysfunction was the highest in those with EP (60% EP, 42% GPP, 19% PsA, 19% PsV). The prevalence of thyroid dysfunction decreased significantly when patients switched from EP to PsV or PsA (58% vs 17%; median, 20.5; range, 4-65 months). Most of the patients with thyroid dysfunction had low thyroxine syndrome (serum levels of free thyroxine are low, but serum thyroid-stimulating hormone level is normal). Patients with thyroid dysfunction demonstrated significantly higher CD3⁺ and CD4⁺ T-cell absolute count levels than those without thyroid dysfunction. Meanwhile, patients with thyroid dysfunction demonstrated lower immunoglobulin (Ig)A and IgM levels than those without thyroid dysfunction. Finally, patients with thyroid dysfunction demonstrated higher elevated serum C-reactive protein levels than those without dysfunction in total, although there were no statistical differences. Our data indicate that thyroid dysfunction in patients with psoriasis may be associated with inflammation caused by psoriasis.