ripheral tissues (Labrie et al., 1995), meaning that it may also have effects through testosterone and estrogen receptors, not only within the brain but also on immune function and bone and muscle growth. For instance, males with 21-hydroxylase deficiency, a condition that leads to the overproduction of DHEA/S, have reduced fertility, as a result of increased estrogen concentrations suppressing gonadotropin stimulation of the testes (Cabrera et al., 2001; Stikkelbroeck et al., 2001). However, such individuals are also likely to have testicular tumors, clouding the implication of these findings for normal maturation.

DHEA/S is known to have a variety of physiological effects during maturation, including promoting muscle and bone growth (Argquitt et al., 1991; Zemel and Katz, 1986) and disease resistance (Kurtis et al., 2001), as well as playing a role in mood (Goodyer et al., 1996). In addition premature adrenarche has been shown to have effects on both cognition and psychosocial development (Dorn et al. 1999; Nass et al. 1990). Though it is unclear how far findings on cognition can be generalized, Goodyer et al. found that DHEA/S hyposecretion was related to major depression in a sample of 8- to 16-year olds, suggesting that DHEA/S does have important effects on mood during development in normal children.

BIOLOGY OF REPRODUCTIVE MATURATION IN HUMAN MALES

To understand the role of reproductive maturation in the development of reproductive behavior in human males, its important to separate various strands, including reproductive maturation, pubertal development, and somatic growth. Reproductive maturation involves maturation of the hypothalamic-pituitary testicular axis. This starts with gonadarche or the beginning of testicular growth and the onset of spermatogenesis and testosterone production by the testes, which plays some role in libido. Pubertal maturation, or the development of secondary sexual characteristics as a consequence of increasing testosterone levels, represents the outward appearance of reproductive maturation and plays a role in changing social status.

Both reproductive maturation and pubertal maturation are necessary conditions for adult maturation common to mammalian species. Somatic growth, on the other hand, is not essential to the beginning of reproduction; in fact, in many species reproductive maturation begins when somatic growth has reached its nadir. In contrast, for humans somatic growth during adolescence includes a reacceleration of growth in both weight and height that has been slowing down ever since infancy, suggesting that the pubertal growth spurt may be a specifically human adaptive feature (Bogin, 1999).

However, more recent work suggests that other primate species exhibit a similar growth spurt (Leigh, 1998) in weight, especially among sexually dimorphic species. Chimp males, for instance, show important gains in



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