Comparative rapidity of response of height, limb muscle and limb fat to treatment with human growth hormone in patients with and without growth hormone deficiency.

The widths of muscle and fat in the upper arm and calf have been measured radiologically before treatment and at intervals of 1, 3. 6 and 12 months during administration of human growth hormone in 41 pre-pubertal patients with "isolated" growth hormone deficiency and in 22 patients with multiple deficiencies following gross CNS lesions. Height was also measured. The curves of response of muscle and fat on the one hand and height on the other were strikingly dissimilar. A very rapid increase of muscle took place in the first month; but after 6 months the increments had fallen to normal values for size and bone age. Decrements in fat followed the same pattern. Height, however, showed a smaller increment in the first month than in the period 1 to 3 months in the "isolated" deficiency cases, and much slower fall back towards normal. The first-year height increment was not at all correlated with the first-month height increment in the "isolated" deficiency cases, though it had a correlation coefficient of 0.46 with the first-month muscle increment. Nine cases of short stature not due to GH deficiency were similarly studied. There was considerable overlap between deficient and non-deficient in all responses in the first 3 months, though children in the top half of the responder's distribution could be distinguished. A 1-month radiological test of responses to hGH in doubtful cases is proposed, using in all only 40 IU of hormone. It is emphasised that a small response of muscle and fat may occur in cases who do nevertheless respond in height to hGH administration; a large response in muscle and fat, however, is indivative that treatment will be effective, though it does not well predict the precise amount of height that may be gained.