PSAT251 Examination of TRH test in Central Hypothyroidism due to Non-Functional Pituitary Adenoma

OBJECTIVES: There is a little evidence for the TRH test criteria in the diagnosis of Central Hypothyroidism (CeH). Therefore, we investigated the significance of the TRH test for Central Hypothyroidism due to Non-Functional Pituitary Adenoma. METHODS: 107 cases of Non-functional pituitary adenoma (NFPA) in Gunma University Hospital Neurosurgery and Toranomon Hospital Intercerebral Pituitary Surgery, between 2007 to 2020 are studied. Subjects divided into CeH group (n = 19) with FT4 below the reference value and a normal group (n = 88). Serum TSH level was determined before (basal-TSH value) and 30, 60, 120 minutes after TRH administration. Peak-TSH value, delayed and prolonged responses were analyzed. A peak-TSH occurring at 60 minutes or later was considered as a delayed response. If 120-minutes TSH value to peak-TSH value ratio is equal to or higher than 0.6 was considered as a prolonged response. RESULTS: The basal-TSH was higher in the CeH group than in the normal group (median 2.7 vs. 1.5μIU/mL) (p <0.01). There was no difference between two groups, in both 30-minute value and the peak value. Delayed response occurred in 10/19 (53%) in the CeH group, and 18/88 (20%) in the normal group (p < 0.01). Prolonged response occurred at a higher rate of 15/19 (79%) in the CeH group, while in 23/88 (26%) in the normal group (p <0.01). AUC was maximum when prolonged response (120-minute value to peak value ratio) is equal to or lower than 0.65. CONCLUSION: In central hypothyroidism due to Non-Functional Pituitary Adenoma, the basal-TSH value does not usually decrease, but rather be higher value within the reference range. 30-minute value or peak value was not useful in diagnosis, yet the prolonged response was more significant. Central Hypothyroidism in Non-Functional Pituitary Adenoma, can be diagnosed with sensitivity of 79% and specificity of 78% when the 120-minute value to peak value ratio is equal to or lower than 0.65. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.