Is thyroid endocrinopathy associated with psoriasis?

A recent study suggests that patients suffering from psoriasis and psoriatic arthritis may have an increased risk of developing autoimmune thyroid disease. 

The question of whether psoriasis is associated with thyroid disease was investigated by researches in Taiwan. Dr. Shu-Hui Wang and colleagues attempted to study the relationship between psoriasis and thyroid disease using Taiwan’s National Health Insurance Research Database (NHRID). They published their results November 2018 in the Journal of the American Academy of Dermatology.

They performed a retrospective study comparing the incidence of thyroid disease in psoriatic patients compared to non-psoriatic patients. Data were extracted with ICD-9 CM coding from the NHRID from January 2000 through December 2011.

Over this span, 162,842 patients with psoriasis were identified. The case psoriatic patients were then age-matched with non-psoriatic controls. The psoriatic patients were further divided into psoriasis alone and psoriasis with psoriatic arthritis.  When comparing psoriatic patients to controls there was an overall increase in the incidence of thyroid disease.

The authors further divided the risk of thyroid disease in their analysis as follows. In psoriatic patients the incidence of hyperthyroidism (adjusted HR 1.22, 95% CI 1.11-1.33), Graves’ disease (adjusted HR 1.26, 95% CI 1.13-1.41), hypothyroidism (acquired) (adjusted HR 1.38, 95% CI 1.23-1.56), thyroiditis (adjusted HR 1.42, 95% CI 217 1.22-1.64), and Hashimoto’ thyroiditis (adjusted HR 1.47, 95% CI 1.18-1.82).

In the psoriatic arthritis group there was a 1.44-fold (95% CI 1.24-1.66), 1.32-fold 220 (95% CI 1.07-1.65), 1.38-fold (95% CI 1.07-1.79), 1.74-fold (95% CI 1.34-2.27), 221 2.05-fold (95% CI 1.51-2.77), and 2.09-fold (95% CI 1.34-3.24) risk for the development of simple nontoxic goiter, hyperthyroidism, Graves’ disease, 223 hypothyroidism, thyroiditis, and Hashimoto’s thyroiditis.

The link between thyroid disease and psoriasis was not elucidated in this retrospective cohort study. The authors however suggest several possible explanations for this phenomenon. Both thyroid disease and psoriatic patients have T-helper 1 cell-mediated inflammation. Furthermore, there are several genes that have been implicated in both psoriasis and thyroid disease such as PTPN22 620W allele and a locus on chromosome 4q27.

This study illustrates that patients suffering from psoriasis have an increased risk of developing autoimmune thyroid disease. This risk increases if the patients are also suffering from psoriatic arthritis. The study’s result reaffirms the complexity of systemic inflammation in psoriasis and reminds clinicians of association between psoriatic patients and thyroid morbidity.

Wang SH, Wang J, Lin YS, Tung TH, Chi CC. Increased risk of incident thyroid diseases in people with psoriatic disease: A cohort study. Journal of the American Academy of Dermatology. 2018 Dec 5.