8342 A Rare Case of a Corticotropic and Gonadotropic Pituitary Double Adenoma

Abstract Disclosure: S. Gruber: None. D. Kirschenbaum: None. T. Hortobagyi: None. C. Serra: None. A. Bink: None. F. Beuschlein: None. Z. Erlic: None. Background: Pituitary adenomas account for about 15% of all intracranial neoplasms and typically arise from monoclonal proliferation of anterior pituitary cells. While lactotropic and clinically hormone-inactive adenomas make up by far the largest proportion, somatotropic and corticotropic adenomas have a significantly lower prevalence. This case describes the very rare finding of a corticotropic and gonadotropic double adenoma. Clinical Case: A 63-year-old Caucasian man (BMI 36.7 kg/m2) presented in the obesity clinic. Hypercortisolism was suspected by repeated lack of cortisol suppression in low-dose dexamethasone suppression tests [minimal 87 nmol/l] and disrupted circadian rhythm of cortisol secretion according to salivary cortisol profile. Cortisol levels in a 24-hour sample of urine were normal. ACTH levels were elevated [73 ng/l; n<61 ng/l] leading to suspicion of Morbus Cushing. Concomitant diseases include sleep apnea, arterial hypertension and newly diagnosed type 2 diabetes mellitus. Medical history was notable for deep vein thrombosis and pulmonary embolism. Other stigmata of hypercortisolism were not evident. The rest of endocrine work up confirmed partial secondary hypothyroidism and hypogondotropic hypogonadism. An MRI of the pituitary gland revealed a pituitary macroadenoma with a maximum dimension of 20 mm. The patient underwent an endoscopic transnasal adenomectomy with post-operative corticotropic insufficiency. Contrary to our expectations, the histological examination of the surgical resection revealed a gonadotrophic pituitary adenoma with SF1 and focal FSH expression. The discrepancy between clinical, biochemical and histological findings led to subsequent examinations of the specimen with detection of an small fragment accounting for less than 5% of the total sample with expression of T-Pit and ACTH but neither SF1 nor Pit-1, corresponding to an additional corticotropic adenoma with densely granulated pattern. The tumor cells did not show overlapping expression patterns of transcription factors or hormones, which indicates the coincidence of two distinct adenomas. Three months postoperatively, the patient is biochemically cured. Partial anterior pituitary insufficiency remained. Conclusion: Pituitary double adenomas are found in 0.5-1.5% of all surgical specimens. They are characterized by their origin from different cell lines, which distinguishes them from plurihormonal adenomas, which originate from one single cell line. Here we demonstrate a SF1-T-Pit lineage combination resulting in a neighboring ACTH and FSH-adenoma. In this particular case, the clinically relevant corticotropic adenoma was comparatively tiny, making it easy to miss. This illustrates well the importance of careful correlation of clinical, laboratory and histologic findings as correct diagnosis is crucial for postoperative patient management. Presentation: 6/2/2024