Subacute thyroiditis in a lateral thyroid gland: evaluation of the pituitary-thyroid axis during the acute destructive and the recovery phases.

Subacute thyroiditis in a lateral, ectopic thyroid has been previously unreported. A 4 10/12-YEAR-OLD GIRL HAD AN ENLARGING MASS IN THE LEFT UPPER ANTERIOR NECK. Initially, the serum concentration of T4 was normal, T3 was elevated, and TSH was undetectable without response to TRH. RAI uptake was 1%. The data were consistent with subacute thyroiditis. Twelve weeks later the serum concentration of T4 was low and TSH was elevated; thyroid replacement therapy was given for 20 weeks. When this was discontinued, there was an initial increase and then a decrease in the TSH values accompanied by an increase in serum concentrations of T3 and T4 to normal during eight weeks. One must consider a lateral ectopic thyroid gland in the differential diagnosis of masses in the neck. Physicians must be aware that temporary hypothyroidism occurs during the course of subacute thyroiditis.