Thyrotropinomas

Thyroid-stimulating hormone (TSH)-secreting pituitary adenomas (thyrotropinomas) are a rare but important cause of hyperthyroidism. Recent studies point to a higher incidence than previously suspected, with a greater proportion of microadenomas. This is likely to reflect, at least in part, the increased use of combined free hormone and TSH measurements to screen for thyroid dysfunction, coupled with improvements in modern magnetic resonance (MR) imaging. The latter has allowed the detection of smaller tumours, but at the same time carries the risk of identifying pituitary incidentalomas that are then falsely identified as the cause of hyperthyroxinaemia with non-suppressed TSH. Accordingly, a systematic approach (combining clinical, biochemical, radiological, and genetic investigations) is required to ensure a robust diagnosis. For most patients transsphenoidal surgery remains the preferred treatment, with somatostatin analogues (SSAs) used to facilitate safe surgery (by normalizing thyroid hormone levels) and as adjunctive therapy when complete surgical resection is not possible. However, emerging data suggests that primary SSA therapy alone is a reasonable option for some patients. Radiotherapy is generally reserved for aggressive (especially SSA resistant) tumours.