Diagnosis of acromegaly in a patient with type 1 diabetes mellitus.

OBJECTIVE

To describe a case of acromegaly in a young patient with poorly controlled diabetes mellitus and suggest guidelines to distinguish acromegaly and high growth hormone (GH) levels previously reported in poorly controlled type 1 diabetes.

METHODS

We present a detailed case report, including clinical findings and serial laboratory results in a patient with type 1 diabetes and a GH-secreting pituitary tumor.

RESULTS

A 28-year-old woman with type 1 diabetes underwent assessment for secondary amenorrhea and worsening glycemic control. A low estradiol level and an inappropriately low level of follicle-stimulating hormone prompted magnetic resonance imaging of the head, which demonstrated a pituitary adenoma. Subsequent endocrine investigation revealed a high insulin-like growth factor I (IGF-I) level (849 mg/L; normal range, 122 to 400). The concentration of insulin-like growth factor-binding protein-3 (IGFBP-3) was also elevated (5.5 mg/L; normal range, 2.0 to 4.2). GH levels measured during episodes of spontaneous hyperglycemia (>180 mg/dL) were in the range of 3 to 5 ng/mL and failed to suppress to below 2 ng/mL after a bromocriptine suppression test. The patient underwent transsphenoidal resection of a pituitary tumor, which stained positively for GH by immunohistochemistry. Postoperatively, glycemic control improved, with decreased fluctuations of hypoglycemia and hyperglycemia, despite a decrease in insulin requirements.

CONCLUSION

This report highlights the difficulty in interpreting GH and IGF-I levels in patients with type 1 diabetes. In addition, a detailed review of the literature suggests that IGFBP-3 measurements may be helpful in confirming the diagnosis of concurrent acromegaly and distinguishing it from high GH levels attributable to poor control of diabetes.