Incidence of thyroid disorders in systemic sclerosis: results from a longitudinal follow-up.

CONTEXT: Systemic sclerosis (SSc) is a connective tissue disease of unknown etiology, and several studies reported its association with thyroid autoimmune disorders. No study has evaluated longitudinally the incidence of new cases of thyroid autoimmunity and dysfunction in patients with SSc.

OBJECTIVE: The purpose of this study was to evaluate the incidence of new cases of clinical and subclinical thyroid dysfunction in a wide group of women with SSc vs an age- and sex-matched control group from the same geographic area. DESIGN AND PATIENTS OR OTHER PARTICIPANTS: After exclusion of sclerodermic patients with thyroid dysfunction (n = 55) at the initial evaluation, the appearance of new cases of thyroid disorders was evaluated in 179 patients and 179 matched control subjects, with similar iodine intake (median follow-up 73 months in patients with SSc vs 94 months in control subjects).

RESULTS: A high incidence (P < .05) of new cases of hypothyroidism, thyroid dysfunction, anti-thyroperoxidase antibody positivity, and appearance of a hypoechoic thyroid pattern in sclerodermic patients (15.5, 21, 11, and 14.6 of 1000 patients per year; respectively) vs that in control subjects was shown. A logistic regression analysis showed that in patients with SSc, the appearance of hypothyroidism was related to a borderline high initial TSH level, anti-thyroperoxidase antibody positivity, and a hypoechoic and small thyroid.

CONCLUSIONS: Our study shows a high incidence of new cases of hypothyroidism and thyroid dysfunction in female sclerodermic patients. Female sclerodermic patients, who are at high risk (a borderline high [even if in the normal range] TSH value, anti-thyroperoxidase antibody positivity, and a hypoechoic and small thyroid) should have periodic thyroid function follow-up.