The cause and course of isolated thyrotropin (TSH) deficiency are not well understood. We report a 65-year-old man with a transient, probable isolated TSH deficiency associated with cavernous sinus syndrome secondary to tympanitis. On his admission, serum TSH and triiodothyronine levels were very low. No TSH response to thyrotropin releasing hormone (TRH) was observed. However, 6 years later, TSH response to TRH was restored. The present case showed that inflammation in the cavernous sinus could be one of the causes of TSH deficiency. Further, it demonstrated that TSH deficiency is not always permanent and the reevaluation of pituitary function is necessary.