Elevated TSH levels in the presence of hyperthyroidism should prompt consideration of a concomitant TSHoma; specific biochemical markers, including a high alpha subunit/TSH ratio, elevated TSH alpha-subunit, and a reduced response of TSH to TRH stimulation, exhibit sensitivities of 83 %, 75 %, and 71 %, respectively [6]. This evidence concerns the gene TRH and TSH-secreting pituitary adenoma.