Adrenal Cushing’s syndrome (CS) is caused by cortisol-producing adrenal adenoma (CPA) and is frequently accompanied with impaired glucose tolerance (IGT) or diabetes mellitus (DM). Previous cross-sectional studies showed that glucose metabolism disorders in CS are characterized by insulin resistance and insufficient β-cell compensation. However, because of the rarity of CS, there are few studies that assessed whether glucose metabolism disorders could be ameliorated by surgical treatment. We evaluated the changes in glucose metabolism before and after surgery for CPA. The participants were 11 (10 female and 1 male) patients with overt adrenal CS, treated with unilateral adrenalectomy for CPA between 20and 2017. Patients with pre-diagnosed DM were excluded. A 75 g oral glucose tolerance test (OGTT) was performed before and after surgery. Using the data from OGTT, insulin resistance and insulin secretion indices were calculated. After surgery, cortisol secretion and body mass index decreased significantly (24 h urinary free cortisol: 582 [321-743] to 31.3 [23.6-40.6] μg/day, p = 0.001, and 25.8 [20.6-26.2] to 21.4 [19.6-24.2], p = 0.0077, respectively). The type of OGTT was largely improved (normal glucose tolerance/IGT/DM: 2/8/1 to 8/3/0). The immunoreactive insulin and glucose levels during the OGTT decreased significantly. The homeostatic model assessment of insulin resistance decreased significantly (2.4 [1.4-2.8] to 1.0 [0.6-1.1], p = 0.002), and the Matsuda index increased significantly (3.0 [2.3-4.5] to 8.2 [6.3-11.4], p < 0.001). In addition, the insulinogenic and disposition indices increased significantly (0.70 [0.22-1.51] to 1.22 [0.78-1.64], p = 0.04, and 609.1 [237.8-1095.2] to 1286.0 [1034.6-1857.6], p = 0.001, respectively).
In conclusion, our study showed that insulin resistance and insulin secretion were largely ameliorated after surgery for CPA, indicating that β cell dysfunction caused by cortisol overproduction is reversible.
K. Miyoshi: None. Y. Tsurutani: Research Support; Self; Astellas Pharma US, Inc.. Speaker's Bureau; Self; Astellas Pharma US, Inc., Amgen Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Merck Sharp & Dohme Corp., Kissei Pharmaceutical Co., Ltd., Kowa Pharmaceuticals America, Inc., Kyowa Hakko Kirin Co., Ltd., Mitsubishi Tanabe Pharma Corporation, Mochida Pharmaceutical Co., Ltd., Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sanofi, Sumitomo Dainippon Pharma Co., Ltd., Takeda. A. Suzuki: None. T. Takiguchi: None. C. Sugisawa: None. J. Saito: None. T. Nishikawa: None.