MON-081 - Monocular Hemianopsia as an Initial Presentation of Somatotroph Macroadenoma

Somatotroph adenomas are a type of neuroendocrine tumor that result in overproduction of growth hormone and clinically presents with acromegaly at time of diagnosis. In our case, we have a 20-year-old male with a complaint of acute left eye blurred vision that began upon waking. MRI brain revealed a large 2.7cm sellar and suprasellar mass lesion with configuration most typical of a large pituitary macroadenoma. The optic chiasm was noted to be markedly thinned, draped along the upper margin of the mass. He was promptly admitted for resection of the pituitary mass. Labs initially showed IGF-1 elevated to 629ng/mL, growth hormone elevated to 9.69 ng/mL, ACTH 55.5pg/mL, FSH 8.7 IU/L, LH 3.9 IU/L, and prolactin 8.0 ng/mL.

The patient underwent transsphenoidal resection with neurosurgery and otolaryngology. Pathology results revealed sheetlike proliferation of cells with neuroendocrine cytomorphology and tumor cells positive for synaptophysin with nuclear labeling for PIT-1, cytoplasmic staining for growth hormone, and abundant fibrous bodies indicative of sparsely granulated somatotroph adenoma. The immunohistochemical profile was positive for synaptophysin with a Ki67 index of 3-4%.

Two weeks after his transsphenoidal resection, he continued to experience polyuria and polydipsia. He continued to have mild blurred vision although improved from his initial presentation. Labs obtained six weeks after post-resection showed stable sodium of 145 mmol/L and GH 1.67. IGF-1 improved to 247, sex hormone binding globulin was 14 nmol/L. At post op week 10, he continues to have some blurred vision which remains stable and polyuria but otherwise feels well. He will require frequent follow up for neuroendocrine tumor monitoring.

Somatotroph adenomas are typically diagnosed as macroadenomas, when the size is significant enough to cause presenting symptoms of acromegaly. While vision change is gradual but evident for unresected macroadenomas, typical initial presentation includes acromegaly rather than abrupt vision change alone. It is important to note that in large tumors with proliferative rates and impingement of the optic chiasm, early resection is favorable for improvement of visual defects.

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