Cardiopulmonary performance during exercise in acromegaly, and the effects of acute suppression of growth hormone hypersecretion with octreotide

We studied 10 adult patients with active acromegaly (4 men and 6 women, mean age 55 ± 5 years and mean body mass index 27.9 ± 1.1 kg/m2). Control values for the echocardiographic and exercise studies were obtained from 10 normal subjects matched for sex and age (5 men and 5 women, age 51.1 ± 3.7 years and body mass index 25.3 ± 1 kg/m2). Each patient underwent: (1) blood sampling for growth hormone (GH) assay every 3 hours; (2) a 2-dimensional, guided M-mode echocardiographic study; and (3) a cycloergometric exercise test at baseline and after treatment with a portable pump infusing octreotide, 500 μg/24 hours subcutaneously. All patients had left ventricular hypertrophy. Systolic function indexes did not significantly differ among normal subjects, whereas baseline Doppler studies showed abnormalities in left ventricular diastolic filling in acromegalic patients. At anaerobic threshold and at maximal exercise, acromegalic subjects sustained a significantly (p < 0.05) decreased workload (54 ± 23 vs 94 ± 11 and 87 ± 37 vs 152 ± 15 W) compared with control subjects. After octreotide, baseline heart rate (79 ± 7 vs 87 ± 8 beats/min, p < 0.05) and serum GH levels significantly decreased compared with levels before administration of octreotide. Systolic and diastolic functional indexes at rest significantly improved after octreotide in acromegalic patients. Both at anaerobic threshold and at maximal exercise, workload and oxygen consumption were significantly increased after octreotide administration. Exercise capacity at anaerobic threshold was not significantly different in acromegalic subjects after octreotide infusion when compared with normal subjects. We hypothesize that elevated circulating GH levels in acromegaly may have a functional negative effect on cardiovascular function at baseline and during exercise. This functional alteration is promptly reversible if GH levels are sustainedly decreased for 24 hours by continuous octreotide infusion.