Beyond the Somatopause: Growth Hormone Deficiency in Adults over the Age of 60 Years

GH secretion declines by 14% decade of adult life, leading to the suggestion that people over the age of 60 yr are functionally GH deficient. If this is the case, one might not be able to detect a difference in GH secretion between the elderly with documented hypothalamic-pituitary disease and an age-matched control group. We studied GH secretion in 24 patients with hypothalamic-pituitary disease and 24 controls matched for body mass index and age using 24-h GH profiles, arginine stimulation tests, and serum insulin-like growth factor I (IGF-I) levels. The median (range) area under the curve of the GH profile [< 9.6 (< 9.6-20) vs. 18.5 (10.7-74.4) micrograms/L.24 h; P < 0.0001], the median stimulated peak GH response to arginine [< 0.4 (< 0.4-7.7) vs. 8.0 (1.6-37.0) micrograms/L; P < 0.0001], and the median serum IGF-I concentration [102 (< 14-162) vs. 147 (65-255) ng/mL; P = 0.0002] were significantly lower in the patients than in the controls. Fifteen patients showed no evidence of spontaneous or stimulated GH secretion, whereas all controls had evidence of both. The area under the GH curve in the 33 subjects with demonstrable GH secretion correlated significantly with the peak GH response to arginine (r = 0.71; P < 0.0001), but not with serum IGF-I concentration. This study suggests that organic GH deficiency in the elderly is distinct from the decline in GH secretion associated with the aging process. These patients may benefit from GH replacement therapy.