Endocrine Abstracts

Background: Muscle weakness persists in patients with acromegaly (ACRO) even long-term after disease control. Mechanisms determining this sustained impairment are not known. We hypothesized that alteration of muscle architecture, due to intramuscular fatty infiltration, is associated with muscle dysfunction in these patients.

Patients and Methods: Thirty-seven acromegalic patients [21 females and 16 males, mean (± s.d.)age, 53 ± 9 years, BMI, 27 ± 4 kg/m² and duration of control, 92 ± 58 months], and 37 age, gender and BMI-matched controls were studied. The degree of fatty infiltration (FF, fat fraction) in the thigh muscles was measured using magnetic resonance imaging (MRI), 2-point Dixon sequence in the anterior, posterior, and combined anterior and posterior compartments, rectus femoris and vastus intermedius. The following muscle function tests were also performed: Gait Speed Velocity (GS), Timed Up and Go (TUG), 30-Second Chair Stand and Hand Grip Strength.

Results: Mean FF (%) in all the compartments analysed was increased in patients as compared with controls (P < 0.01 for all the comparisons). ACRO female patients had greatermean FF in the anterior (29.2 ± 6.8% vs 20.5% ± 3.9%, P < 0.01), posterior (38% ± 8.4% vs 27% ± 5%, P < 0.01), combined anterior and posterior compartments (33.7% ± 7% vs 23.7% ± 4%, P < 0.01),rectus femoris (28.9% ± 8% vs 16.9% ± 4.9, P < 0.01) and vastus intermedius (21.3% ± 5.6 vs 14.9% ± 2%, P < 0.01), as compared with males. Gait speed was slower in ACRO patients as compared with controls (1.18 ± 0.2 vs 1.33 ± 0.2 P < 0.05). Performance on TUG was worse in ACRO women as compared with ACRO men (6.5 ± 1.1 vs 5.5 ± 1 for TUG; P < 0.05). Greater mean intramuscular FF in all the compartments analysed was associated with worse performance on TUG (P < 0.01), in patients only. Muscle mass and intramuscular FF in both posterior and combined anterior and posterior compartments were associated with IGF-I SDS in ACRO men only (r = 0.49 and r = 0.54, P < 0.05 for both correlations). Thirty-second chair stand was negatively associated with GH in ACRO men only (P < 0.05). In a multiple linear regression model, female gender and older age predicted intramuscular FF in the combined anterior and posterior compartment (β = 0.49; P < 0.05), in ACRO patients. Intramuscular FF of the combined anterior and posterior compartments predicted the performance on TUG after adjusting for gender and age (β = 0.75, P < 0.01) in ACRO. Conclusions: Intramuscular fatty infiltration is increased in ACRO patients with long-term control of the disease, especially in females. ACRO females also present with poorer muscle function than males. Intramuscular fat accumulation may be one of the mechanisms underlying sustained muscle weakness in acromegaly.