Clinical and subclinical autoimmune thyroid disorders in systemic sclerosis

Several studies have reported the association of systemic sclerosis (SSc) with thyroid autoimmune disorders, but most of them have neither an appropriate control group nor include a complete thyroid work-up.

The aim of our study was to evaluate the prevalence of thyroid disorders in a large number of patients with SSc using a complete clinical evaluation.

Thyroid-stimulating hormone (TSH), free triiodothyronine, free thyroxine, antithyroglobulin and antithyroid-peroxidase (AbTPO) autoantibodies, thyroid ultrasonography and blood flow and fine needle aspiration were performed in 202 SSc patients versus 404 gender- and age-matched controls from the general population, with similar iodine intake, to evaluate the prevalence of clinical and subclinical thyroid disorders.

Odds ratio (OR) for female SSc versus controls was: for subclinical hypothyroidism, 3.2 (95% CI)=1.8-5.7); for clinical hypothyroidism, 14.5 (95% CI=2.3-90.9); for AbTPO positivity, 2.7 (95% CI=1.8-4.1); for hypoechoic pattern, 3.2 (95% CI=2.2-4.7); for thyroid autoimmunity, 3.7 (95% CI=2.6-5.4); for thyroid volume <6 ml, 1.8 (95% CI=1.2-2.7). OR for thyroid autoimmunity in male SSc versus controls was 10.8 (95% CI=2.2-52.4). Mean values of TSH in female SSc, and of AbTPO in female and male SSc were higher (P<0.01) than in controls. We observed three cases of Graves' disease in female SSc versus zero in controls (P=0.0140), and two cases of papillary thyroid cancer in SSc patients.

Thyroid function, AbTPO and ultrasonography should be tested as part of the clinical profile in SSc patients. Females, subjects with positive AbTPO and hypoechoic and small thyroid should have thyroid function follow-up and appropriate treatment in due course.