OBJECTIVE: Subacute thyroiditis (SAT) is a transient inflammatory disease of the 
thyroid. We evaluated the clinical characteristics based on laboratory and 
imaging studies in patients with SAT before treatment.
PATIENTS: We reviewed the medical records of 852 patients (107 men and 745 
women) with SAT who visited our thyroid clinic at Kuma Hospital from 1996 
through 2004.
RESULTS: SAT developed most often in female patients aged 40 to 50 years, with 
significant seasonal clusters during summer to early autumn. While the rates of 
any virus infections and diseases did not differ from those in the general 
population, recurrent episodes of SAT at intervals of 13.6+/-5.6 years accounted 
for 1.6% of all cases. At the onset of SAT, 28.2% of patients had temperatures 
greater than 38 degrees C and typical symptoms associated with thyrotoxicosis 
developed in more than 60% of patients. Before treatment, most of the abnormal 
laboratory findings associated with thyrotoxicosis, inflammation, and liver 
dysfunction reached peak levels within 1 week after onset. Ultrasound 
examination showed that half of the patients with unilateral thyroid pain 
presented with bilateral hypoechogenic area in the thyroid and the rate of 
bilateral hypoechogenic area tended to increase 2 months after onset.
CONCLUSION: Laboratory studies of thyroid dysfunction and inflammation related 
to SAT presented peak levels within 1 week after onset.