Endocrine Abstracts

JOINT2595

Co-secretion of growth hormone (GH) and prolactin occurs in approximately 25% of GH-secreting tumors. Monomorphic expression of a single cell type producing both GH and prolactin occurs in the mammosomatotroph adenoma (MSA), while dimorphic expression of two cell types separately secreting GH and prolactin occurs in the mixed somatotroph-lactotroph adenoma (MSLA). Compared to pure GH-secreting adenomas, co-secreting adenomas are associated with younger age, larger tumor size, greater tumor invasion, and more frequent presurgical hypopituitarism. We retrospectively reviewed the medical records of patients at our medical center with a histopathological diagnosis of MSA (n = 19) or MSLA (n = 3) following surgical resection from 2021 to 2024. The mean age at surgery was 48 years and 64% were female. Preoperative symptoms included headache (68%), irregular menses (60%), acromegalic features (59%), arthralgias (45%), and visual disturbances (36%). Comorbidities included hyperlipidemia (59%), glucose intolerance (45%), colon polyps (45%), thyroid nodules (41%), hypertension (36%), obstructive sleep apnea (36%), and carpal tunnel syndrome (27%). Preoperatively, the average prolactin level was 53 ng/ml, GH level 17 ng/ml, and IGF-1 level 856 ng/ml. Radiographically, the majority were macroadenomas (91%) with cavernous sinus invasion in 45%, suprasellar extension in 41%, and optic chiasm compression in 23%. T2-hypointensity was noted in 27%. Tumor size did not correlate with IGF-1 levels. All tumors stained positive for GH, prolactin, and PIT-1. Somatic mutations in GNAS were detected in 32%. Resection was subtotal in 7 cases (32%). The postsurgical remission rate was 50%. The frequencies of postoperative hypogonadism, hypothyroidism, and adrenal insufficiency were 27%, 18%, and 45%, respectively, with recovery in 17% and 25% for hypogonadism and adrenal insufficiency, respectively. There was one case of postoperative total anterior hypopituitarism and no cases of permanent AVP deficiency. With regards to methylation data, the identified pituitary adenoma classes were pituitary adenoma, STH densely granulated, group B (n = 14), pituitary adenoma, STH sparsely granulated (n = 5), pituitary adenoma, TSH (n = 2), and pituitary adenoma, STH densely granulated, group A (n = 1) with a positive calibrated score (>0.9) in 82%. Both cases of pituitary adenoma, TSH class were associated with a score below threshold. To our knowledge, this is the first study examining the different methylation classes in GH and prolactin co-secreting tumors. Further investigation is needed to better characterize these co-secreting adenomas and how they differ both from their pure GH-secreting counterparts as well as amongst themselves to guide prognosis and management with consideration for tumor methylation data as a potential tool.