Long-term follow-up of 106 multiple sclerosis patients undergoing interferon-beta 1a or 1b therapy: predictive factors of thyroid disease development and duration.
BACKGROUND
Conflicting data have been reported on the association between interferon (IFN)-beta therapy of multiple sclerosis (MS) patients and thyroid disease development.


OBJECTIVE
The goals of this study are as follows: to assess the actual occurrence of thyroid dysfunction and autoimmunity during long-term IFN-beta therapy; to establish the possible presence of predictive factors for thyroid dysfunction development and duration; and to suggest an effective follow-up protocol for patients receiving long-term IFN-beta therapy.


METHODS
A total of 106 MS patients (76 women) underwent IFN-beta 1a or 1b therapy for up to 84 months (median, 42 months). Thyroid function and autoimmunity were assessed at baseline and every 3-6 months throughout the treatment course.


RESULTS
Baseline thyroid autoimmunity was detected in 8.5% of patients and hypothyroidism in 2.8%. Thyroid dysfunction (80% hypothyroidism, 92% subclinical, 56% transient) developed in 24% (68% with autoimmunity) of patients and autoimmunity in 22.7% (45.5% with dysfunction), without significant differences between the two cytokines; 68% of dysfunctions occurred within the first year. Autoimmunity emerged as the only predictive factor for dysfunction development (relative risk, 8.9), whereas sustained disease was significantly associated with male gender (P < 0.003).


CONCLUSIONS
Both incident thyroid autoimmunity and dysfunction frequently occur in MS patients during IFN-beta therapy, particularly within the first year of treatment. Thyroid dysfunction is generally subclinical and transient in over than half of cases; preexisting or incident autoimmunity emerged as the only significant predictive factor for thyroid dysfunction development. Thyroid function and autoimmunity assessment is mandatory within the first year of IFN-beta therapy; thereafter, serum TSH measurement only in patients with thyroid disease could be sufficient.
Caraccio
N
N
Department of Internal Medicine, University of Pisa, via Roma 67, 56126 Pisa, Italy.
Dardano
A
A
Manfredonia
F
F
Manca
L
L
Pasquali
L
L
Iudice
A
A
Murri
L
L
Ferrannini
E
E
Monzani
F
F
D000328:Adult; D015551:Autoimmunity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D000068556:Interferon beta-1a; D000068576:Interferon beta-1b; D016899:Interferon-beta / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000188:drug therapy*; D013959:Thyroid Diseases / Q000209:etiology*; D013961:Thyroid Gland / Q000276:immunology; D013997:Time Factors
D000068576:Interferon beta-1b; D016899:Interferon-beta; D000068556:Interferon beta-1a