Growth at puberty: interaction of androgens and growth hormone.

Puberty is characterized by the onset and continued development of secondary sexual characteristics and an abrupt onset of linear growth. Growth in boys occurs due to the rising levels of androgens and also indirectly mediated by growth hormone (GH) and the insulin-like growth factors. Data are presented to show marked androgen-dependence of GH increases at puberty. The mode of this increase is through an augmentation in the amplitude of the pulses rather than in their frequency. Shortly after the maximal rate of growth, the pattern of GH release reverts toward that of the prepubertal child. To investigate the neuroendocrine mechanism through which androgens increase the mean circulating GH level, deconvolutional analysis has been applied. At mid-puberty the maximal rate of GH release per secretory burst and the total amount released per burst were increased. There were no significant alterations in the duration or frequency of the GH secretory burst or in the serum half-life reflecting the metabolic clearance of the hormone. Thus, the pubertal growth spurt in boys is likely subserved by the altered neurosecretory dynamics for GH. These altered hormone levels likely produce the equally profound changes in body composition, regional fat distribution, and muscular strength that occur during puberty in boys.