BACKGROUND: Oral glucocorticoids are administered in moderate and severe cases 
of subacute thyroiditis (SAT), providing dramatic relief from pain and fever. 
However, there have been no reports regarding the optimal dose of prednisolone 
(PSL) for treatment of SAT. In this study, we used 15 mg/day of PSL as the 
initial dosage and tapered it by 5 mg every 2 weeks. We assessed the 
effectiveness of this treatment protocol.
METHODS: We examined 384 consecutive and untreated patients with SAT who visited 
our thyroid clinic between February 2005 and December 2008. We excluded patients 
who did not fit our protocol, and the final number of subjects was 219. When 
patients complained of pain in their neck or C-reactive protein (CRP) was still 
high, physicians were able to extend the tapering of the dose of PSL or increase 
it at 2-week intervals. The endpoint of the study was the duration of the PSL 
medication. We also compared the severity of thyrotoxicosis and rate of 
hypothyroidism after SAT between the short medication group (patients who 
recovered within 6 weeks) and long medication group (patients who recovered in 
12 weeks or more).
RESULTS: The number of patients whose thyroiditis improved within 6 weeks and 
did not recur was 113 (51.6%), and 61 (27.9%) improved within 7 to 8 weeks and 
did not have a recurrence. The longest duration was 40 weeks. Seven patients 
(3.2%) needed increases in the dosage of PSL. Thyroid hormone (free thyroxine 
and free triiodothyronine) levels measured at the initial visit in the short 
medication group were significantly higher than those in the long medication 
group (p<0.05). Serum CRP, male-to-female ratio, body weight, and age showed no 
differences between the two groups. There were no differences in the rate of 
hypothyroidism after SAT between the two groups (p=0.0632).
CONCLUSIONS: The treatment protocol that we employed had 15 mg/day of PSL as the 
initial dosage for the treatment of SAT, with tapering by 5 mg every 2 weeks, 
and was effective and safe for Japanese patients. However, 20% of patients with 
SAT needed longer than 8 weeks to recover from the inflammation.