6619 An Unlikely Cause of Oligomenorrhea: Acromegaly Secondary to a Sparsely Granulated, Somatotroph-Lactotroph Adenoma

Abstract Disclosure: S.I. Alicea: None. Y. Wu: None. J. Marquez: None. C.S. Botero Suarez: None. M. Kinaan: None. Introduction: Acromegaly most commonly presents as a pituitary tumor that causes excessive production ofgrowth hormone (GH); and rarely due to excess of GHRH or ectopic production of GH. Approximately 15% of surgically removed pituitary adenomas represent GH-producing neoplasms, and about 5% are bihormonal, secreting both GH and prolactin (PRL). We present a case of an unexpected presentation of oligomenorrhea which ended up with the diagnosis of acromegaly secondary to plurihormonal mixed somatotroph-lactotroph sparsely granulated adenoma. Case Description A 32-year-old female with history of prediabetes was referred to our clinic by her gynecologistfor evaluation of oligomenorrhea which was initially attributed to polycystic ovarian syndrome.She reported menarche at age 10 and has experienced irregular menses and periods of amenorrhea over the years. Physical exam revealed macroglossia, a widened thickened nose, acanthosis nigricans in the neck skin folds, facial hair thickening, and significant thickening of all fingers, toes and soft tissues. Given physical exam findings, we evaluated the patient for acromegaly and lab testing revealed markedly high IGF I, mildly elevated prolactin, and hemoglobin A1C of 5.7%. An MRI of the brain with IV contrast revealed a heterogeneously enhancing pituitary macroadenoma measuring 2.9 x 2.9 x 2.2 cm with suprasellar extension resulting in mass effect on the optic chiasm without definite cavernous sinus extension. She was started on Cabergoline 0.5mg twice weekly temporarily and underwent pituitary transsphenoidal resection. Pathology results revealed tumor cells that were positive for Chromogranin and Cam5.2. About 10% of cells showed immunoreactivity for Prolactin and negative for TSH, ACTH, FSH, LH and immunostains. There was also weak focal (about 2%) immunoreactivity for GH. Occasional mitotic figures were present. The MIB-1 proliferation index was 3%. The reticulin stain demonstrates loss of acinar architecture, supporting the diagnosis. Aside from transient sodium fluctuations consistent with triphasic response, she had no long-lasting postoperative complications. One month after her surgery, her IGF I level and hemoglobin A1C are trending down and she reports symptomatic relief. She continues follow up in our clinic. Discussion This patient has acromegaly secondary to a mixed somatotroph-lactotroph sparsely granulated adenoma. Sparsely granulated adenomas are more common in younger populations, can be more aggressive, and are less responsive to somatostatin analogs. Early detection and treatment is imperative in the prevention of complications secondary to the disease. Our case will closely examine the differences in the clinical, prognostic, and pathologic features of sparsely- vs. densely granulated adenomas. We will also discuss the effects of acromegaly on gonadal function. Presentation: 6/1/2024