Lower Visceral and Subcutaneous but Higher Intermuscular Adipose Tissue Depots in Patients with Growth Hormone and Insulin-Like Growth Factor I Excess Due to Acromegaly

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Abstract
Context: GH and IGF-I are important regulators of metabolism and body composition. In acromegaly, a state of GH and IGF-I excess, the lipolytic and insulin antagonistic effects of GH may alter adipose tissue (AT) distribution. Objectives: Our objective was to test the hypothesis that in acromegaly whole-body AT mass is less and to examine for the first time the relationship between GH/IGF-I excess and intermuscular AT (IMAT), an AT depot associated with insulin resistance in other populations. Design, Setting, and Patients: We conducted a cross-sectional study in 24 adults with active acromegaly compared with predicted models developed in 315 healthy non-acromegaly subjects. Outcome Measures: Mass of AT in the visceral AT (VAT), sc AT (SAT), and IMAT compartments from whole-body magnetic resonance imaging and serum levels of GH, IGF-I, insulin, and glucose were measured. Results: VAT and SAT were less in active acromegaly (P < 0.0001); these were 68.2 ± 27% and 79.5 ± 15% of predicted values, respectively. By contrast, IMAT was greater (P = 0.0052) by 185.6 ± 84% of predicted. VAT/trunk AT ratios were inversely related to IGF-I levels (r = 0.544; P = 0.0054). Acromegaly subjects were insulin resistant. Conclusions: VAT and SAT, most markedly VAT, are less in acromegaly. The proportion of trunk AT that is VAT is less with greater disease activity. IMAT is greater in acromegaly, a novel finding, which suggests that increased AT in muscle could be associated with GH-induced insulin resistance. These findings have implications for understanding the role of GH in body composition and metabolic risk in acromegaly and other clinical settings of GH use.

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