8188 Pituitary hyperplasia resulting from primary hypothyroidism: A case report

Abstract Disclosure: M. Aziz: None. M.I. Manolas: None. V. Tabatabaie: None. L. Rincon: None. Pituitary hyperplasia resulting from primary hypothyroidism: A case report.Background: Primary hypothyroidism is a common endocrine condition seen in 4.6% of USpopulation (1). We describe an uncommon presentation of prolonged severe primaryhypothyroidism leading to significant hyperplasia of the pituitary gland resembling a pituitarymacroadenoma. Clinical Case: A 34-year male with schizophrenia and Hashimoto’s hypothyroidism diagnosedat the age of 17 presented with hallucinations, chest pain, fatigue, and dyspnea. The patient hada 15-year history of uncontrolled hypothyroidism with persistently elevated TSH with values ashigh as 2,299 (n 0.30-4.20 uU/mL) due to poor adherence to levothyroxine. Initial laboratorystudies revealed hyponatremia (Na 130, n135-145 mEq/L), elevated TSH (>100, n0.30-4.20 uU/mL), undetectable FT4 (<0.4, n0.6-1.5 ng/dL) and elevated CK (5671, n<200 U/L).Levothyroxine was restarted at dose of 150 mcg daily. Head CT performed for evaluation ofaltered mental status and hallucinations revealed hyperdensity within the pituitary gland,concerning for underlying hemorrhage and apoplexy. Neurosurgical consultation was requested,and a pituitary MRI was obtained in preparation for potential surgical intervention. MRI showeda prominent anterior pituitary gland measuring up to 14 mm with homogeneous enhancementwithout evidence of hemorrhage. In the absence of any hemorrhage or definitive mass, thepituitary enlargement was considered secondary to the long-standing history of uncontrolledprimary hypothyroidism leading to pituitary hyperplasia, and surgical intervention was deemedunnecessary. Repeat labs 1 week later showed TSH >100uU/mL, FT4 0.6 ng/dL, CK 2799 andrepeat MRI showed slight decrease in size of the pituitary gland, confirming hyperplasiasecondary to severe, prolonged hypothyroidism. Conclusion: Prolonged primary hypothyroidism can lead to pituitary hyperplasia which can bemistaken as pituitary macroadenoma, leading to unnecessary surgical intervention. Carefulreview of history and TSH trends can help elucidate this diagnosis. References: (1) Wyne KL, Nair L, Schneiderman CP, et al. Hypothyroidism Prevalence in theUnited States: A Retrospective Study Combining National Health and Nutrition ExaminationSurvey and Claims Data, 2009-2019. J Endocr Soc. 2022;7(1):bvac172. Published 2022 Nov10. doi:10.1210/jendso/bvac172 Presentation: 6/3/2024