Subacute thyroiditis. Eleven cases with histological confirmation and thyrotrophic response to thyrotrophin releasing hormone.

Eleven cases are reported of subacute thyroiditis with histopathological study; there were 9 females and 2 males. Bacteriological studies were inconclusive. Different stages of pathological involvement were observed at the same time in all patients. The clinical course followed the classical pattern in most cases: hyperthyroid-like, hypothyroid-like phase and recovery. Blood TSH assessment before and after TRH stimulation revealed an early phase of depression unresponsive to TRH, followed by high levels with marked stimulation; during the first phase, radioiodine uptake was low, but was enhanced by exogenous TSH administration; accordingly the low uptake seems to be due to low TSH levels and not to complete destruction of the thyroid gland. Failure of TSH levels to rise after TRH stimulation is typical of this stage of the disease. Although the final outcome is not yet predictable in some patients, definitive myxoedema appears to be probable in two cases.