PMON132 Biochemical and Radiologic Discordance in the Post-operative Surveillance of a Filipino Patient With Acromegaly

BACKGROUND: Trans-sphenoidal surgery is the recommended initial therapy in patients with acromegaly. Early cure rate is 80-90% for microadenomas and <50% for macroadenomas. The goal is a serum IGF-1 that is normal for age and gender with GH <1mcg/L by immunoradiometric or chemiluminescent assays. CLINICAL CASE: A 71-year old male who consulted for diabetes management was eventually worked up for acromegaly He presented with coarsened facial features, hoarse voice, frontal bossing and enlarged hands and feet. Medical history includes hypertension, hepatosplenomegaly, colonic polyposis, obstructive sleep apnea and nasal septal deviation post-repair. Laboratory tests showed elevated IGF-1 (566.15, n: 91-282 ng/ml) and non suppressed GH after 75g OGTT (50.1, n<2.47 ng/mL). Pituitary hormonal profile showed normal prolactin (98.13, n: 86-324 mIU/L), TSH (1.63, n: 0.27-4.2 uIU/ml), FT4 (17.78, n: 12-22 pmol/L), ACTH (35, n: 7.2-63.3 pg/mL), Cortisol (387.4, n: 172-497 nmol/L), LH (4.56, n: 1.7-8.6 mIU/mL) and FSH (15.4, n: 1.5-12.4 mIU/mL). Contrast-enhanced pituitary MRI revealed a 1.5×2.0×1.9 cm pituitary macroadenoma with compression of the optic chiasm. Patient underwent trans-phenoidal surgery and excision of the tumor. Histopathology revealed a homogenous cells in sheets, acidophilic, densely granular and consistent with sommatotrophs, mammotrophs and sommatomammotrophs. Post-procedure GH was normal (2.731 ng/mL). Two months post-operatively, there was a significant decrease in both GH (1.84 ng/mL) and IGF-1 levels (258.59 ng/mL) while other pituitary hormones all within reference range. Contrast-enhanced pituitary MRI at 2 months showed interval surgical removal of the mass, with decompression of the optic chiasm. Clinically, there was softening of facial features and improvement in his voice. His cranial did not show pituitary mass. However, repeat GH after 75g OGTT (0.37 ng/mL, 2.3 ng/mL) and IGF-1 (361 ng/mL, 523,6 ng/mL) at 9 and 12 months post-surgery, respectively, were found above the reference range. CONCLUSION: Discordance between anatomic and biochemical testing must be investigated thoroughly considering pulsatile hormone secretion, comorbidities and possible microscopic residual disease. Testing with the same assay is important to avoid inter-assay variability. Post-operative monitoring should be done at 12 weeks as it may take time for IGF-1 to normalize. If IGF-1 remains elevated, medical, surgical, radiotherapy, or combination may be considered especially in the presence of an identifiable focus. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.