Endocrine Abstracts

Background: 20% of patients with acromegaly can have visual field defect due to compression of optic chiasm. This patient presented with visual field defect but no evidence of pressure effect on optic chiasm, but later found to have pituitary macroadenoma and acromegaly.

Clinical Details: 59 yr old man presented 7 years ago to ophthalmologist with left inferior field defect of 2 months duration. The field defect was confirmed with perimetry. Subsequent CT scan of orbit, optic nerve, brain and MRI scan of brain were all reported to be normal at that time. Lebers optic atrophy was ruled out by genetic testing. His final diagnosis was ischemic optic neuritis followed by atrophy. 2 years later the patient developed Type 2 diabetes and hypertension for which he was followed up in the diabetic clinic. His diabetes is poorly controlled in spite of large dose of insulin (HbA1c always above 10 grams%).

During his recent visit to the diabetes annual review clinic he was found to have clinical features of acromegaly. His random growth hormone level was 294 milliunits/litre(normal 12 milliunits/l)and insulin like growth factor was 592 micrograms/litre (normal less than 300 micrograms/litre). Subsequent glucose tolerance test with growth hormone confirmed the diagnosis of acromegaly. MRI scan of the pituitary showed a 1.8 cm pituitary macroadenoma, which has suprasellar extension but no definite compression of the optic chiasm. The patient was started on a somatostatin analogue and was referred to neurosurgeons.

Conclusion: In acromegaly field defect can occur without actual invasion of optic chiasm though it is rare. Pituitary function test and imaging should be done in all patients with undiagnosed field defects to prevent delay in diagnosis as in this patient.