Body Composition and Ectopic Lipid Changes With Biochemical Control of Acromegaly

Abstract

Context: Acromegaly is characterized by growth hormone (GH) and insulinlike growth factor-1 (IGF-1) hypersecretion, and GH and IGF-1 play important roles in regulating body composition and glucose homeostasis.

Objective: The purpose of our study was to investigate body composition including ectopic lipids, measures of glucose homeostasis, and gonadal steroids in patients with active acromegaly compared with age-, body mass index (BMI)-, and sex-matched controls and to determine changes in these parameters after biochemical control of acromegaly.

Design: Cross-sectional study of 20 patients with active acromegaly and 20 healthy matched controls. Prospective study of 16 patients before and after biochemical control of acromegaly.

Main outcome measures: Body composition including ectopic lipids by magnetic resonance imaging/proton magnetic resonance spectroscopy; measures of glucose homeostasis by an oral glucose tolerance test; gonadal steroids.

Results: Patients with active acromegaly had lower mean intrahepatic lipid (IHL) and higher mean fasting insulin and insulin area under the curve (AUC) values than controls. Men with acromegaly had lower mean total testosterone, sex hormone-binding globulin, and estradiol values than male controls. After therapy, homeostasis model assessment of insulin resistance, fasting insulin level, and insulin AUC decreased despite an increase in IHL and abdominal and thigh adipose tissues and a decrease in muscle mass.

Conclusions: Patients with acromegaly were characterized by insulin resistance and hyperinsulinemia but lower IHL compared with age-, BMI-, and sex-matched healthy controls. Biochemical control of acromegaly improved insulin resistance but led to a less favorable anthropometric phenotype with increased IHL and abdominal adiposity and decreased muscle mass.

Figure 1.

Axial T1-weighted images of the abdomen at the level of L1-2 and L4 and the proximal and midthigh of a 75-year-old woman with acromegaly (A) before and (B) after biochemical control of the disease. After therapy, there was an increase in abdominal and thigh subcutaneous adipose tissue (black asterisks) and visceral adipose tissue (+) and a decrease in muscle mass (white asterisks).

Figure 2.

Proton magnetic resonance spectroscopy of the right hepatic lobe in a 56-year-old man with acromegaly obtained (A) before and (B) after biochemical control of the disease. IHL increased after therapy. For purposes of visual comparison, the amplitudes of unsuppressed water are scaled identically.