Endocrine Abstracts

Background: Active acromegaly induces insulin resistance despite a lean phenotype, both of which reverse by curative surgery. The impact of somatostatin analogue treatment on insulin sensitivity is less certain and may be offset by its anti-lipogenic effects.

Aim: To study insulin sensitivity, body composition and extopic lipid content in newly diagnosed patients with acromegaly before and ≥6 months after successful surgical or medical treatment.

Patients and methods: 21 patients with acromegaly underwent a hyperinsulinemic, euglycemic glucose clamp (HEC), dual x-ray absorptiometry (DXA) scan, and MR spectroscopy to quantify lipid content in liver (IHL) and muscle (IMCL).

Results: 10 patients were controlled by surgery alone and 11 patients were controlled by a somatostatin analog (SA). Mean±S.E. serum IGF-I levels (μg/l) before and after treatment were 696±90 and 221±33 with no treatment-specific difference either before (P=0.75) or after treatment (P=0.11). Insulin sensitivity assessed by mean±SE glucose infusion rate (GIR) during the HEC (mg/kg per min) increased after treatment (P=0.001) regardless of modality (P=0.505) [GIR: 3.3±0.4 (before) vs. 4.7±0.5 (after)]. Disease control induced a 17% increase in total body fat (P=0.001) and 8% decrease in lean body mass (P<0.000). IHL (% CH2/water) increased after disease control, regardless of modality: 2.8±0.6 (before) vs. 6.7±2.2 (after) (P=0.04). IMCL did not change in either group.

Conclusions: 1) The improvement in insulin sensitivity and change in body composition after disease control of acromegaly appear independently of treatment modality, 2) Our data extend and support the notion that IHL is a GH target, 3) Acromegaly and its treatment exemplifies that insulin sensitivity and body composition do not always walk hand in hand.