Do the new TSH reference ranges have any implications for the diagnosis of TSH-secreting tumours?
Leeds, U.K. Carole Spencer Ph.D., FACB.: I do not think the setting of the TSH reference limits relates to the diagnosis of TSH secreting pituitary tumor which are detected in patients with biochemically high thyroid hormone levels and paradoxically DETECTABLE TSH. The TSH might only be in the 0.05-0.1 mIu/L range and be paradoxically high if the patient had very high thyroid hormone levels and/or was exhibiting symptoms of thyroid hormone excess. The differential diagnosis in this case rests more with excluding heterophilic antibody (HAMA) as the cause of the paradoxically high TSH (by blocker tube and testing TSH by different manufacturers assays) before embarking on expensive sella imaging. Why is the assumption made (on page 24) that the TSH distribution should be simple Gaussian (thereby justifying cutting off the upper tail of the observed TSH distribution)? Log-normal distributions are not uncommon in endocrinology, particulary for trophic hormones that participate in negative f
