RF13 | PMON92 Chance or Pedigree?: A Rare Case of Familial ACTH Producing Pituitary Tumor

BACKGROUND: ACTH secreting pituitary adenomas are rare accounting for only 5-10% of pituitary adenomas. Most often these are sporadic, however there are rare associated familial disorders and genetic mutations. This case highlights a 41-year-old male with an ACTH secreting macroadenoma similar to one found in his brother previously. CASE: A 41-year-old male with no significant medical history presented to the hospital with headaches and visual changes for the past week and decreased libido, weight gain, and cold intolerance for the past year. Physical exam demonstrated left eye ptosis, proptosis, and pupillary dilation with intact visual fields, as well as Cushingoid features including BMI 35.1, abdominal obesity with striae, enlarged breasts and tanned skin. Family history revealed a brother diagnosed with an ACTH producing pituitary microadenoma requiring surgical resection 18 years prior.Brain MRI revealed a 2.6×2.5×3.7 cm sellar mass with optic chiasm compression and pituitary apoplexy. Labs revealed elevated ACTH 708 pg/mL (7.2–63 pg/mL) suggesting a functional macroadenoma, as well as signs of early hypopituitarism with TSH 0.37 uIU/mL (0.35-5.50 uIU/mL), free T4 0.5 ng/dL (0.5-1.3 ng/dL), free T3 2.6 pg/mL (2.3–4.2 pg/mL), prolactin 2.0 ng/mL (2.6-13.1 ng/mL), GH 0.2 ng/mL (</= 7.1 ng/mL). He received Dexamethasone and Levothyroxine before undergoing transsphenoidal resection which confirmed an ACTH-secreting macroadenoma resulting in Cushing's disease. Given his family history, he underwent evaluation for MEN (multiple endocrine neoplasia) which revealed normal gastrin, calcium, calcitonin, PTH and chromogranin A. Furthermore, the patient and his brother underwent genetic testing which was negative for mutations associated with isolated familial pituitary adenomas (including MEN1, CDKN1A, PRKAR1A, AIP). After discharge, he was started on testosterone and transitioned to hydrocortisone with plans for ACTH stimulation test and steroid taper as tolerated. CONCLUSION: Pituitary adenomas are fairly common, and most tend to be sporadic. ACTH secreting pituitary adenomas are rare and in rarer instances can be inherited as isolated tumors or as part of multiple endocrine neoplasia syndrome [1]. Early identification of genetic predisposition can allow for screening of associated comorbidities and early screening in family members. The patient and his brother both had rare ACTH-secreting adenomas, however genetic testing for genes associated with familial disorders was unrevealing in this case. While it is possible that the ACTH secreting tumors in both brothers were sporadic or due to environmental exposure, it is also possible that they share a genetic mutation not yet identified. REFERENCES: [1] Dworakowska D, et al. The pathophysiology of pituitary adenomas. Best Practice & Research Clinical Endocrinology & Metabolism. 2009;23(5): 525-541. Presentation: Sunday, June 12, 2022 1:24 p.m. - 1:30 p.m., Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.