Figures & data
Figure 1 Major components of the GH neuroregulatory system. Question marks on the arrows leading from the stomach indicate uncertainty about the physiological role of gastric ghrelin in the regulation of GH; and on arrows from ghrelin in the hypothalamus indicate uncertainty as to whether ghrelin found in the hypothalamus is synthesized in neurons there, or is synthesized elsewhere and acts at hypothalamic or pituitary levels. IGF-1 is synthesized in many GH target tissues, but more than 85% of circulating IGF-1 is liver-derived. From CitationAnawalt and Merriam 2001.
Figure 2 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 CitationHo et al 1987.
Figure 3 Effects of a single intravenous bolus of GHRH on GH secretion in healthy subjects of different ages. While the highest responses are seen in young adults, there is no significant decrease with aging, and pituitary GH responses are well preserved even in the oldest subjects. From CitationPavlov et al 1986.
Table 1 Clinical features of the adult GHD syndrome
Table 2 Effects of GH replacement in GHD adults