Endocrine Abstracts

Introduction: Hypopituitary patients with GHD tend to have a reduced exercise capacity. GH is secreted during exercise, has a strong lipolytic action and has been shown to be positively correlated with exercise performance. We hypothesized that the lack of GH leads to a reduced systemic availability of free fatty acids (FFA) during exercise thereby affecting exercise performance.

Methods: Patients with GHD and matched sedentary control subjects (CS) were exposed to an increasing workload on a treadmill for the determination of VO_2max. On a separate day, the patients and CS performed a 2-h exercise session on a treadmill (50–60% of the VO_2max). Usual hydrocortone replacement therapy was administered prior to exercise as needed. Blood samples were taken at baseline and every 30 min during the exercise. Analysis of the samples included GH, catecholamines (noradrenaline, adrenaline) as well as glucose and FFA. Area under the curve (AUC) as well as peak concentrations of hormones and metabolites were analyzed.

Results: Ten patients with GHD (four females, age: 42.5±12.4, years, mean±S.D.; BMI: 26.6±3.8 kg/m²; waist: 89.3±12.9 cm) and 10 CS matched for gender, age, BMI and waist (age: 42.8±12.6 years; BMI: 25.2±5.3 kg/m²; waist: 90.7±19.1 cm) volunteered for the study. GHD patients tended to have a reduced VO_2max compared with CS (GHD: 36.3±6.7 ml O₂/kg per bodyweight; CS: 41.7±6.0, P=0.07). GH-AUC and GH peak concentrations were lower in GHD patients compared to CS (by a factor 15). AUC and peak concentrations of catecholamines were similar in patients and CS. FFA-AUC, Glucose-AUC and glucose peak concentrations were not significantly different between the two groups. GHD patients tended to have lower FFA peak-concentrations compared to sedentary controls (patients: 1.03±0.39 mmol/l; CS: 1.51±0.53; P=0.054).

Conclusion: This study indicates that i) there is a tendency towards a reduced exercise capacity in GHD patients compared to matched control subjects and ii) systemic availability of FFA may be slightly reduced whereas glucose availability is similar during exercise in GHD.