HORMONE AND RECEPTOR STUDIES - RELATIONSHIP TO LINEAR GROWTH IN CHILDHOOD AND PUBERTY

Preliminary data suggested different patterns of hormonal control of linear growth in males and females. To better define these patterns, serum samples were collected from 75-125 boys and a similar number from girls for each year of age between 3-16 yr (n = 2416). Fewer samples were collected from 2-yr-olds, newborns, and adults (n = 151). Samples for each age were aliquoted, combined, and assayed for GH, GH-binding protein (GHBP), insulin-like growth factor-I, and testosterone. GHBP, expressed as a percentage of the [I-125]GH bound, increased yearly in males and females, with no relationship to the secretion of sex hormones. The increase in binding of [I-125] GH and, by inference, GH receptors occurred at a greater rate between the ages of 2-10 yr than between 10-16 yr (in terms of absolute binding, 1.2 +/- 0.11% vs. 0.38 +/- 0.04% yearly; P < 0.001). In each age group, however, the increase in GHBP exhibited a strong positive correlation with linear height (r = 0.96-0.98 in males; r = 0.92-0.99 in females). Before puberty, GH and insulin-like growth factor-I concentrations were consistently greater in females. Between 10-16 yr of age, height velocity (centimeters of growth per yr) correlated strongly with GH in girls (r = 0.86), but did not correlate with GH in boys of a similar age (r = -0.13). The major pubertal growth spurt in males strongly correlated with a rise in serum testosterone concentration beginning at age 11 yr (r = 0.92). Small peaks of GH secretion before and after the major period of accelerated growth in males possibly prolonged the major growth phase, but did not initiate it.