Ectopic Acromegaly Arising from a Pituitary Adenoma within the Bony Intersphenoid Septum of a Patient with Empty Sella Syndrome.

OBJECTIVE: To describe the work-up and treatment of rare ectopic acromegaly caused by a biopsy-proven somatotroph pituitary adenoma located within the bony intersphenoid septum of a patient with empty sella syndrome (ESS). METHODS: We report the presentation, clinical course, diagnostic work-up, and lesion localization and treatment challenges encountered in a 55-year-old patient, with a brief review of relevant literature. RESULTS: A 55-year-old African-American man presented with acromegaly and ESS. Attempts to definitively localize the causative tumor were unsuccessful, though petrosal sinus sampling supported central growth hormone production and imaging suggested bone-enclosed subsellar pituitary tissue. Endoscopic endonasal transphenoidal exploration was undertaken with resection of a somatotroph pituitary microadenoma, and subsequent clinical improvement and biochemical remission. Retrospective review revealed the patient's pituitary to have been located ectopically within a unique bony intersphenoid septum. CONCLUSION: This report describes the first known case of an ectopic pituitary adenoma located within the midline bony intersphenoid septum, which we postulate to have resulted from anomalous embryological pituitary migration. Intra-intersphenoid septal tumors should be considered in cases of apparent central acromegaly with ESS or absence of tumor tissue within the paranasal sinuses or other peripheral locations. INDEXING: Acromegaly, ESS, pituitary adenoma, sphenoid sinus septum.

Pseudoinsulinoma in a white man with autoimmune hypoglycemia due to anti-insulin antibodies: value of the free C-Peptide assay.

OBJECTIVES: Insulin autoimmune syndrome (IAS) is an extremely rare cause of hypoglycemia, particularly in non-Asian populations. METHODS: In this report, we describe a white male patient with elevated total insulin (>100.0 µIU/mL), C-peptide, and proinsulin levels who was diagnosed with IAS due to anti-insulin antibodies. He also had a small IgG κ M-protein. RESULTS: We show that anti-insulin antibodies and/or the monoclonal protein can significantly interfere with insulin and C-peptide immunoassays and propose polyethylene glycol precipitation to quantitate free C-peptide levels as a useful assay in differentiating IAS due to anti-insulin antibodies from insulinoma. CONCLUSIONS: In patients presenting with hypoglycemia with excessively high insulin levels, consideration needs to be given to autoimmune hypoglycemia due to anti-insulin antibodies as a cause. Additionally, if total C-peptide levels are increased, free C-peptide needs to be quantitated following polyethylene glycol precipitation.