Growth hormone secretory dynamics in subjects with normal stature

Children of short stature may be tested to detect a deficiency in growth hormone (GH). This test involves artificially stimulating the secretion of GH and then measuring the level of this hormone in the blood. Recently the validity of this testing has been questioned, arguing that a child may test normally when GH secretion is artificially stimulated, but the child still may not be spontaneously producing adequate quantities. A more valid test may be to measure the level of GH produced spontaneously. Forty-six normal seven to 18 year old children participated in this study. Levels of GH in these normal adolescent and preadolescent children were monitored over a 24-hour period. The amount of GH secreted spontaneously varied widely during that time. Peaks of GH secretion occurred at various times during waking and sleeping, but the greatest amount was secreted during sleep. There was an increase in spontaneous GH secretion seen in the adolescent. GH values for normal children were found to overlap those found in children who had a proven growth hormone deficiency and short stature. This study failed to show a relationship between a child's height and his level of GH, measured over a 24-hour period. The data suggested that for normally growing children, the amount of GH circulating in the blood may not be the primary factor determining height; genetic influences may be more important.