Diagnosing Thyroid-Stimulating Hormone (TSH)-Secreting Pituitary Adenomas by Short-Term Somatostatin Analogue Test

Abstract

Background: Diagnosis of thyroid-stimulating hormone (TSH)-secreting pituitary adenomas (TSHoma) before surgery remains a challenge, especially microadenomas. We aimed to establish a short-term somatostatin analogues (SSA) test to differentiate TSHoma from resistance of thyroid hormone (RTH). Methods: We first evaluated the sensitivity and specificity of SSA test in a retrospective cohort (TSHoma, N=32; RTH, N=20). We then applied the SSA test in a perspective SITSH cohort without THRB gene mutation (pituitary microadenoma, N=10; negative pituitary imaging, N=7). Findings: In the retrospective cohort, both TSHoma and RTH patients showed a decrease of TSH at the start of the SSA test, but the velocity of TSH slowly decreased in RTH patients after 2 h. The suppression ratio of TSH at 24 h versus 2 h and 0 h in TSHoma patients was remarkably greater than in RTH patients. The 24 h versus 2 h suppression ratio showed the best diagnostic accuracy at a cut-point of 44·46%, with sensitivity as 95·00%, specificity as 93·75%. In the perspective cohort, 10/17 patients diagnosed as TSHoma with mean TSH suppression ratio of 68·91%, in which seven patients with microadenoma received pituitary surgery and achieved euthyroid with positive TSH staining in the resected tissues. Interestingly, two patients with negative pituitary imaging showed TSH suppression ratio greater than 44·46% and developed microadenomas at follow-up. Interpretation: A short-term SSA test provides an alternative diagnostic approach for TSHoma, especially microadenoma. It may also diagnose TSHoma in very early stage before positive findings in pituitary imaging. Funding Statement: This study was sponsored by the grants from National Science Foundation of China (81570702, 81400772, 81700686). Foundation of Health and Family planning Commission of Shanghai (20174Y0204). National International Science Cooperation Foundation (2015DFA30560). The National Key Research and Development Program of China (2016YFC0901503). Declaration of Interests: The authors state: No conflicts of interest to declare. Ethics Approval Statement: The board of medical ethics of Ruijin Hospital approved the study, and all patients provided informed written consent.