Acromegaly associated with type 2 diabetes showing normal IGF-1 levels under poorly controlled glycemia

Acromegaly is caused by excessive secretion of growth hormone (GH), and a resultant persistent elevation of insulin-like growth factor-1 (IGF-1) levels. Diabetes mellitus is accompanied in some acromegalic patients with insulin resistance. We encountered a type-2 diabetic patient who had a poorly controlled glycemic state and was diagnosed as acromegaly with normal IGF-1 levels. The patient showed definite acromegalic features. However, in the first screening test, GH levels were high and IGF-1 levels were inappropriately normal so the results were not close to the diagnosis of acromegaly. After moderate glycemic control, an oral glucose suppression test was performed, showing no suppressed GH response. TRH test revealed paradoxical increases in growth hormone levels and a brain MRI discovered a pituitary adenoma. After several-months insulin treatment, IGF-1 levels were increased to the abnormal state and GH levels were decreased without treatment for acromegaly. Here we report the rare case of acromegaly that presents inappropriately normal IGF-1 levels at the time of diagnosis in uncontrolled type 2 diabetic patient and shows increased IGF-1 levels after glycemic control with insulin therapy. When evaluating acromegaly in type 2 diabetes under poorly controlled glycemia, cautious IGF-1 analysis is needed after sufficient glycemic control.