A controlled prospective study was conducted to determine whether thyroid d
isorders are present with increased frequency in patients with MS. We found
that thyroid disorders were at least three times more common in women with
MS than in female controls. This was accounted for mainly by the prevalenc
e of hypothyroidism among the female MS patients. Because hypothyroidism is
usually due to Hashimoto's thyroiditis, its association with MS may suppor
t the hypothesis of autoimmune pathogenesis for MS. Our findings might have
therapeutic implications because interferon treatment can induce antithyro
id antibodies and thyroiditis.