High Prevalence of Antithyroid Antibodies in a New Zealand Cohort of Patients With Systemic Sclerosis.

Background: Autoimmune thyroid disease affects 1% of the general population, and autoimmune thyroid antibodies are noted in up to 15%.

Objective: We hypothesized systemic sclerosis (SSc) is associated with higher prevalence of antithyroglobulin (anti-Tg) and anti-thyroid peroxidase (anti-TPO) antibodies) to justify monitoring of thyroid function for earlier detection and treatment.

Methods: Waikato Hospital SSc clinic patients were prospectively tested for thyroid function tests and antithyroid antibodies (ATAs).

Results: Of the 75 patients with SSc and 10 patients with SSc overlap syndrome (SOS) followed up in the SSc clinic, anti-Tg and anti-TPO were prospectively tested in 61 (70.6%) of the 85 patients. The cohort comprised 38 patients with limited cutaneous SSc (lcSSc), 15 with diffuse cutaneous SSc, and 8 with SOS.Anti-Tg and anti-TPO antibodies were found in 34.2% in lcSSc patients and 33.3% in diffuse cutaneous SSc patients, whereas in SOS they were found in 25% (Tg) and in 12.5% (TPO) of patients.At baseline, 10 patients (11.7%) had thyroid dysfunction: 8 (9.4%) with subclinical hypothyroidism and 1 each (1.2%) with subclinical hyperthyroidism and with clinical hyperthyroidism.After 18 months, 1 woman with lcSSc, positive for both ATAs, developed clinical hypothyroidism.

Conclusions: There is a higher prevalence of ATAs in SSc and SOS compared with the general population. Screening these patients for ATAs is a reasonable measure.