The prepubertal testis: a quiescent or a silently active organ?

The development of the testis is characterised by dramatic changes between birth and adulthood. The most conspicuous changes take place during puberty, when the seminiferous tubule diameter increases significantly owing to an important proliferation of germ cells, giving rise to spermatozoa, and to the development of a tubular lumen; in the interstitial tissue characteristic Leydig cells appear and secrete high levels of testosterone. These pubertal changes of the testis can be detected clinically since they result in testicular volume and serum androgen level increments. The prepubertal testis has classically been defined as a quiescent organ. However, since adequate stereological methods for microscopic analysis are available, it has been shown that the male gonad triplicates its volume between birth and the onset of puberty. Sertoli cells and spermatogonia proliferate intensely; this is critical for the development of quantitatively normal adult spermatogenesis. Seminiferous tubule volume increases owing to an increment in tubular length, not diameter. Sertoli cells are also functionally active during childhood: they produce high amounts of anti-Müllerian hormone during the whole prepubertal period, and inhibin B until the age of 2-4 years. Anti-Müllerian hormone and inhibin seem to play a role as modulators of the proliferation and differentiation of Leydig cell precursors.