Criteria of cure and follow-up of central hyperthyroidism due to thyrotropin-secreting pituitary adenomas

The recorded number of patients with central hyperthyroidism due to TSH- secreting pituitary adenoma doubled in the last few years after the introduction of ultrasensitive TSH assays in the assessment of thyroid function; however, information about the results and the criteria for cure after pituitary surgery is scanty. Seventeen patients with a TSH-secreting adenoma, diagnosed on the basis of detectable TSH levels in the face of high free thyroid hormone concentrations and pituitary lesion at neuroimaging, underwent pituitary surgery. Hypersecretion of other pituitary hormones was diagnosed in 5 of 17 patients. Four patients were initially misdiagnosed and treated with thyroid surgery or radioiodine therapy. The majority (86%) of hyperthyroid patients normalized thyroid hormone concentrations and regained euthyroidism, although pituitary imaging, α-subunit, and α-subunit/TSH molar ratio normalized in only 47%, 54%, and 58% of patients, respectively. Moreover, TSH secretion was normally suppressed by T₃ in 40% of the patients. Interestingly, the finding of undetectable TSH levels 7 days after surgery was highly predictive of successful outcome. During long term follow- up, there was one relapse of hyperthyroidism. Early diagnosis of TSH- secreting adenomas permits a high rate of remission of hyperthyroidism after surgery. However, normalization of thyroid function alone does not necessarily reflect complete removal of the tumor, and more comprehensive criteria of cure based on pituitary imaging, hormone measurement, and suppression of TSH during T₃ administration should be used. Lastly, all patients need an accurate long term follow-up to monitor the possible recurrence of the adenoma.