Abstract 95: Coexisting pituitary adenoma and primary hypothyroidism: Unique case series

Introduction: Markedly elevated thyroid stimulating hormone (TSH) in patient withsellar-suprasellar mass generally indicates pituitary hyperplasia but very rarely primary untreated hypothyroidism and pituitary adenoma may co-exist. It is crucial to differentiate these two conditions, because of significant difference in treatment modalities. Here, we report a caseseries of pituitary adenoma with markedly elevated TSH. Methods: Case records of sella-suprasellar masses with elevated TSH (> 20 mIU/ml), registered between January 2021 and September 2022 were reviewed and those with the diagnosis of pituitary adenoma are included. The diagnosis of pituitary adenoma was based either on histopathology or radiological characteristics compatible with pituitary adenoma with no lesion size reduction with levothyroxine replacement. Results: A total of five patients (4 males) presented at a median age of 37 (range: 23-62) years with headache (n = 4) and visual disturbances (n = 3) Median TSH level was 115.5 (range: 84-430) mIU/ml. Two patients had coexisting central hypocortisolism and hypogonadism. Magnetic resonance imaging revealed macroadenomas with heterogeneous enhancement in all patients. Optic chiasm compression and dome shaped elevation were seen in three patients each. None (n = 4) of the patients showed reduction in lesion size after 3 months of levothyroxine replacement. Three patients underwent surgery and histological confirmation as pituitary adenoma. Conclusion: We report a unique series of pituitary macroadenomas with markedly elevated TSH due to coexisting primary hypothyroidism. This series cautions that all sellar masses with markedly elevated TSH are not pituitary hyperplasia. Baseline imaging characteristics and assessment of lesion size reduction after levothyroxine replacement help to differentiate pituitary adenoma from pituitary hyperplasia.