HISTOLOGY OF SKELETAL-MUSCLE IN ADULTS WITH GH DEFICIENCY - COMPARISON WITH NORMAL MUSCLE AND RESPONSE TO GH TREATMENT

The histology of needle biopsy specimens of skeletal muscle from the vastus lateralis was quantitatively assessed in a group of adults with growth hormone (GH) deficiency, most of whom had hypopituitarism treated with conventional pituitary hormone replacement. The mean age of the 21 patients (16 males and 5 females) was 39 +/- 2 (SEM). Comparisons were made with age- and sex-matched controls following six months double-blind, placebo-controlled treatment with recombinant human GH (rhGH) in the GH-deficient patients. Before treatment, needle muscle biopsies from patients with GH deficiency showed mean type I and II fibre areas of 5,153 +/- 273 and 4,828 +/- 312-mu-m2 respectively, which did not differ from the controls (4,482 +/- 306 and 4,699 +/- 310-mu-m2). Percentages of type I fibres were similar in the two groups (47.2 +/- 2.5 % in GH deficiency and 45.3 +/- 2.2 % in controls). No difference in the variability of type I or II fibre areas was demonstrated between the groups. Correlations between the relative contribution to total fibre area by type I fibres (mean fibre area X percent) and maximal oxygen uptake (p = 0.006), and between type II fibres and quadriceps force (p = 0.035) were noted in GH-deficient adults before treatment. Following rhGH treatment, no change was noted in mean fibre areas, variability of fibre areas, or percentage of either fibre type. We conclude that in adults with GH deficiency: (a) no consistent histological evidence of myopathy was seen; (b) qualitatively, the muscle fibres function similarly to normal, and (c) rhGH treatment does not result in any detectable change in fibre areas or proportion.