Leydig cell development in humans, although for years described as being biphasic, with fetal and adult phases of maturation, is better considered as a triphasic developmental phenomenon. The morphological literature is summarized in this commentary. Although the majority of studies are of a qualitative nature and many questions remain as to the relative and absolute numbers of cells involved in these developmental phases, this literature is more consistent with a triphasic developmental pattern. This view of Leydig cell development is in accord with the well-known triphasic history of testosterone production, i.e. peaks at 14-18 weeks of fetal life, 2-3 months after birth, and from puberty throughout adult life. It is also significant that the neonatal phase of testosterone production is dependent upon reactivation of the hypothalamic-pituitary-testicular axis (HPT). The current interest in the functional implications of the neonatal period will be better served by considering human Leydig cell development as triphasic.

This article has been cited by other articles:

				C. Bodo and E. F. Rissman The Androgen Receptor Is Selectively Involved in Organization of Sexually Dimorphic Social Behaviors in Mice Endocrinology, August 1, 2008; 149(8): 4142 - 4150. [Abstract] [Full Text] [PDF]

				A. Ferlin, A. Garolla, F. Rigon, L. Rasi Caldogno, A. Lenzi, and C. Foresta Changes in Serum Insulin-Like Factor 3 during Normal Male Puberty J. Clin. Endocrinol. Metab., September 1, 2006; 91(9): 3426 - 3431. [Abstract] [Full Text] [PDF]

				S. Ramaswamy Pubertal Augmentation in Juvenile Rhesus Monkey Testosterone Production Induced by Invariant Gonadotropin Stimulation Is Inhibited by Estrogen J. Clin. Endocrinol. Metab., October 1, 2005; 90(10): 5866 - 5875. [Abstract] [Full Text] [PDF]

				S Ramaswamy, C R Pohl, G R Marshall, and T M Plant A switch from continuous to episodic testicular testosterone release in response to pulsatile LH stimulation in juvenile rhesus monkeys (Macaca mulatta) J. Endocrinol., October 1, 2004; 183(1): 61 - 68. [Abstract] [Full Text] [PDF]

				E. B. Berensztein, M. I. Sciara, M. A. Rivarola, and A. Belgorosky Apoptosis and Proliferation of Human Testicular Somatic and Germ Cells during Prepuberty: High Rate of Testicular Growth in Newborns Mediated by Decreased Apoptosis J. Clin. Endocrinol. Metab., November 1, 2002; 87(11): 5113 - 5118. [Abstract] [Full Text] [PDF]

				N. Pitteloud, F. J. Hayes, A. Dwyer, P. A. Boepple, H. Lee, and W. F. Crowley Jr. Predictors of Outcome of Long-Term GnRH Therapy in Men with Idiopathic Hypogonadotropic Hypogonadism J. Clin. Endocrinol. Metab., September 1, 2002; 87(9): 4128 - 4136. [Abstract] [Full Text] [PDF]