NEW ORLEANS — Physiologic doses of growth hormone can increase exercise capacity in adults with growth hormone deficiency, as well as improve their body composition and lipid levels, Jostein Hallen, M.D., said at the annual meeting of the Endocrine Society.
The 7% increase in exercise capacity that he found in his placebo-controlled study “is similar to what you would see if you put a similar population on a training program,” said Dr. Hallen of Norwegian University of Sport and Physical Education, Oslo.
The small study included 55 patients with adult-onset growth hormone deficiency; 96% had multiple pituitary hormone deficiencies; 4% had isolated growth hormone deficiency. Mean body mass index for men was 29; the mean BMI for women was 26. Average subject age was 48.5 years.
As many patients were already taking growth hormone, the study began with a 4-month washout period. Then, subjects were randomized to 9 months of placebo or growth hormone. Subjects' therapy was titrated to acheive an insulin-like growth factor-1 (IGF-1) level within the upper normal range for their age and sex. Final mean daily dose was 0.4 mg for men and 0.6 mg for women.
At outset, subject exercise capacity was determined by treadmill, increased until exhaustion occurred. Body composition was measured by dual-energy x-ray absorptiometry. Three quality-of-life scales were completed.
In men who took growth hormone, the mean IGF-1 levels increased from 95 mg/L to 216 mg/L; in women, the mean level increased from 68 mg/L to 186 mg/L. Subjects in the study group lost an average of 1.9 kg of fat and gained 1.8 kg of lean body mass. Their total and LDL cholesterol levels both dropped an average of 0.5 mmol/L.
Compared with placebo, growth hormone treatment increased the subjects' maximal oxygen uptake by 6%. Endurance increased by 7% over baseline in the study group.
There were no significant effects on quality of life, Dr. Hallen said, who is an investigator for Pfizer Inc. The company funded the study and supplied the drug.