Glucocorticoid response in amiodarone-induced thyrotoxicosis resulting from destructive thyroiditis is predicted by thyroid volume and serum free thyroid hormone concentrations.
BACKGROUND
Amiodarone-induced thyrotoxicosis (AIT) resulting from destructive thyroiditis (type 2) is commonly treated with glucocorticoids, but time needed to restore euthyroidism may be unacceptable for patients with underlying cardiac disorders.


OBJECTIVE
The objective of this prospective study was to identify factors affecting the response to glucocorticoids in a large cohort of patients with type 2 AIT followed prospectively.


METHODS
This study was conducted at university centers.


METHODS
Sixty-six untreated patients with type 2 AIT were enrolled in the study.


METHODS
All patients were treated with prednisone (initial dose, 0.5 mg/kg.d) as long as needed to restore euthyroidism, defined as cure of AIT.


METHODS
The main outcome measure was cure time.


RESULTS
The median cure time was 30 d (95% confidence interval, 23-37 d). Serum free T4 concentration (picograms per milliliter) and thyroid volume (milliliters per square meter) (and, to a lesser extent, serum free T3 concentration) at diagnosis were the main determinants of response to glucocorticoids, with a cure hazard ratio of 0.97 (95% confidence interval, 0.95-0.99; P = 0.005) and 0.84 (95% confidence interval, 0.77-0.91; P = 0.000) for unit of increment, respectively. AIT was cured in all patients with a complete follow-up; euthyroidism was reached in 30 d or less in 60% of patients but in more than 90 d in 16%. A prompt control of thyrotoxicosis (<or=30 d of treatment) was more frequent (77%) in patients with serum basal free T4 concentration no greater than 50 pg/ml and thyroid volume (normalized for body surface area) no greater than 12 ml/m2. The cure probability and the mean cure time in an individual patient can be obtained using a formula generated by multiple regression models.


CONCLUSIONS
Baseline serum thyroid hormone concentrations and thyroid volume help identify patients with type 2 AIT at risk of a delayed response to glucocorticoids.
Bogazzi
Fausto
F
Department of Endocrinology, University of Pisa, Ospedale Cisanello, Via Paradisa, 2, 56124 Pisa, Italy. f.bogazzi@endoc.med.unipi.it
Bartalena
Luigi
L
Tomisti
Luca
L
Rossi
Giuseppe
G
Tanda
Maria Laura
ML
Dell'Unto
Enrica
E
Aghini-Lombardi
Fabrizio
F
Martino
Enio
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000638:Amiodarone / Q000009:adverse effects*; D000889:Anti-Arrhythmia Agents / Q000009:adverse effects*; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D005938:Glucocorticoids / Q000008:administration & dosage*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D013961:Thyroid Gland / Q000000981:diagnostic imaging; D013966:Thyroiditis / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000453:epidemiology; D013971:Thyrotoxicosis / Q000139:chemically induced / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000453:epidemiology; D013974:Thyroxine / Q000097:blood*; D016896:Treatment Outcome; D014284:Triiodothyronine / Q000097:blood*; D018615:Ultrasonography, Doppler, Color
D000889:Anti-Arrhythmia Agents; D005938:Glucocorticoids; D014284:Triiodothyronine; D000638:Amiodarone; D013974:Thyroxine