aging 4 fig 1

Legend-: Patterns of GH secretion in younger and older women and men.
There is a marked age-related decline in GH secretion in both sexes and a loss of the nighttime enhancement of GH secretion seen during deep (slow-wave) sleep. This decrease is primarily due to a reduction in GH pulse amplitude, with little change in pulse frequency. L = large GH pulses, S = small GH pulses. From Ho et al. 1987 (4).