Growth hormone substitution titrated to obtain IGF-I levels in the physiological range in hypopituitary adults: effects upon dynamic strength, endurance and EMG

Abstract

We studied the effects of individualised growth hormone (GH) substitution, aiming at normal insulin-like growth factor I (IGF-I) levels, on biomechanical output and surface electromyogram (EMG) of isokinetic muscle strength and endurance performance in 18 hypopituitary adults and compared with 17 matched healthy controls. The muscle function tests consisted of isokinetic contractions of the right knee extensors, from which torque and EMG were recorded. Three patients were excluded from the final analysis of the muscle function tests due to technical errors and one control subject moved from the area during the study. We found that GH-deficient adults without GH substitution were weaker and had less endurance than healthy control subjects. At the group level, plasma levels of IGF-I were normalised but generally no significant effects upon biomechanical output and EMG were found after dose titration and 6 months of a constant GH dose. However, subjects with the largest changes in IGF-I had significantly better biomechanical output and EMG compared to those with small changes in IGF-I. This finding may indicate that the net increase in IGF-I levels is critical for improvements in biomechanical output, EMG and perception of fatigue to occur.

The effects of five‐year growth hormone replacement therapy on muscle strength in elderly hypopituitary patients

“…8,43 Furthermore, in a study by Ekman et al, 44 hypopituitary patients with the largest changes in IGF-I in response to GH replacement had better biomechanical output than patients with small changes in IGF-I. This is in line with previous observations that GH as well as IGF-I are of importance for muscle morphology, function, and metabolism.…”

“…This is in line with previous observations that GH as well as IGF-I are of importance for muscle morphology, function, and metabolism. 8,43 Furthermore, in a study by Ekman et al, 44 hypopituitary patients with the largest changes in IGF-I in response to GH replacement had better biomechanical output than patients with small changes in IGF-I. No correlation, however, was found in the present study between the change in serum IGF-I concentration and the change in any measure of muscle function.…”

Growth hormone deficiency with late-onset hypothalamic hypoadrenocorticism associated with respiratory and renal dysfunction: a case report

“…Adult patients with CPHD have been reported to show impairment of ventilatory function, and GH-replacement therapy can help restore it [4,11,12]. It has also been reported that GH-replacement therapy for GHD in adults results in increased maximal oxygen uptake, presumably due to increased respiratory muscle strength [13] and increased mean frequency of the surface electromyogram of the muscle fiber area in quadriceps [14]. However, only one report appears to have described severe respiratory failure requiring use of NPPV [12].…”