Acromegaly with Normal IGF-1 Levels Probably due to Poorly Controlled Diabetes Mellitus

Acromegaly with Normal IGF-1 Levels Probably due to Poorly Controlled Diabetes Mellitus

ZENEI ARIHARA,¹ KANAKO SAKURAI,¹ SHOZO YAMADA,² OSAMU MURAKAMI³ and KAZUHIRO TAKAHASHI⁴

¹Department of Endocrinology and Metabolism, KKR Suifu Hospital, Mito, Japan
²Department of Hypothalamic and Pituitary Surgery, Toranomon Hospital, Tokyo, Japan
³Division of Nephrology, Endocrinology and Vascular Medicine, Tohoku University School of Medicine, Sendai, Japan
⁴Department of Endocrinology and Applied Medical Science, Tohoku University Graduate School of Medicine, Sendai, Japan

Acromegaly is characterized by the somatic disfigurement and excessive production of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Here we report a patient with aromegaly and diabetes mellitus, who showed normal IGF-1 levels in spite of elevated GH levels. The patient was a 52-year-old woman with acromegalic manifestations. Serum GH level was elevated (32.4 ng/mL) with hyperglycemia (fasting plasma glucose, 277 mg/dL) and an extremely high level of glycosylated hemoglobin (HbA1c 17.7%), whereas serum IGF-1 level was within normal range (110 ng/mL, normal range 37-266). Brain magnetic resonance imaging detected a pituitary tumor, with involvement of the right cavernous sinus. Oral glucose tolerance test (OGTT) showed no suppression of serum GH. Thyrotropin-releasing hormone test showed paradoxical increases in serum GH. We therefore diagnosed acromegaly accompanied with diabetes mellitus. A large amount of insulin (34 units/day) was required to control the blood glucose level. The patient was treated with octreotide, a somatostatin analogue, followed by transsphenoidal surgery. After the surgery, serum GH levels were suppressed by OGTT, although basal serum GH levels remained to be high. Basal serum GH levels, however, were normalized 5 months later. Blood glucose became well controlled by the diet alone. In contrast, serum IGF-1 increased to the range of 219-233 ng/mL. Pre-operative serum IGF-1 levels were low probably due to poorly controlled diabetes mellitus. In conclusion, the presence of normal serum IGF-1 levels cannot exclude the diagnosis of acromegaly especially when the patient is accompanied by diabetes mellitus.

keywords —— Acromegaly; Insulin-like Growth Factor-1 (IGF-1); Growth Hormone (GH); octreotide; transsphenoidal surgery.

===============================

Tohoku J. Exp. Med., 2008, 216, 325-329

Correspondence: Zenei Arihara, M.D., Ph.D., Department of Endocrinology and Metabolism, KKR Suifu Hospital, 1-1, Akatsuka, Mito, Ibaraki 311-4141, Japan.

e-mail: zari@mx6.nisiq.net