The precursor cells for adult Leydig cells begin their transformation at approx 10 yr of age, and differentiation is complete by 13 yr of age (33). During puberty, the number of adult Leydig cells increases and reaches a maximum of 5x108 per testis in the early 20s (25). At this time, a third peak in testosterone concentrations occurs. Thereafter, Leydig cell numbers gradually decrease by 50% in men aged 60 yr and older (34). Between ages 20 and 60 yr, there is an equilibrium in the numbers of Leydig cells, which comprise approx 4% of the volume of the mature testis (14). The overall scheme of human Leydig cell development is summarized in Fig. 3.
Was this article helpful?