Long-term outcome of thyroid function after amiodarone-induced thyrotoxicosis, as compared to subacute thyroiditis.
BACKGROUND
Two main forms of amiodarone- induced thyrotoxicosis (AIT) exist: type 1 AIT is a condition of true hyperthyroidism developing in patients with pre-existing thyroid disorders, and usually requires thyroid ablative treatment. On the other hand, type 2 AIT is a form of destructive thyroiditis occurring in normal thyroids, the management of which usually consists in glucocorticoid treatment.


OBJECTIVE
To assess the long-term outcome of thyroid function in a prospective study of type 2 AIT patients, as compared to patients with De Quervain's subacute thyroiditis (SAT).


METHODS
Sixty consecutive patients with type 2 AIT were evaluated during oral glucocorticoid treatment (oral prednisone 30 mg/day, gradually tapered and withdrawn over a 3-month period) and followed for 38+/-4 months (range 6-72) thereafter. Sixty consecutive patients with SAT, referred to our Institutes during the same period and treated with the same therapeutic schedule, served as controls.


RESULTS
Type 2 AIT patients were older (p<0.0001) and showed a larger male preponderance (M:F 3.6:1 vs 0.5:1, p<0.0001) than SAT patients. Mean serum free T4 (FT4) and free T3 (FT3) concentrations at diagnosis were increased in both conditions, but higher in type 2 AIT than in SAT (FT4 47.6+/-18.8 and 29.6+/-8.3 pmol/l, respectively, p<0.0001; FT3 15.4+/-7.0 and 11.2+/-3.0 pmol/l, respectively, p<0.001). Correction of thyrotoxicosis was obtained in all patients in both groups, but restoration of euthyroidism occurred earlier in SAT than in type 2 AIT (p=0.006). Ten type 2 AIT patients (17%) and 3 SAT patients (5%, p<0.03) became permanently hypothyroid after glucocorticoid withdrawal and required levothyroxine replacement.


CONCLUSIONS
A relevant proportion of type 2 AIT patients develop permanent hypothyroidism after correction of thyrotoxicosis. Thus, periodic surveillance of thyroid status is required after type 2 AIT.
Bogazzi
F
F
Department of Endocrinology and Metabolism, University of Pisa, 56124 Pisa, Italy. f.bogazzi@endoc.med.unipi.it
Dell'Unto
E
E
Tanda
M L
ML
Tomisti
L
L
Cosci
C
C
Aghini-Lombardi
F
F
Sardella
C
C
Pinchera
A
A
Bartalena
L
L
Martino
E
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000638:Amiodarone / Q000009:adverse effects*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000502:physiology*; D013968:Thyroiditis, Subacute / Q000139:chemically induced* / Q000503:physiopathology / Q000628:therapy; D013971:Thyrotoxicosis / Q000139:chemically induced* / Q000503:physiopathology / Q000628:therapy; D013997:Time Factors; D016896:Treatment Outcome
D000638:Amiodarone