The major androgens secreted by these cells is testosterone and secretion begins 8 to 10 weeks after conception. Testosterone secretion reaches a peak at 12 to 14 weeks, and declines to very low levels by the end of the second trimester (about 21 weeks). Levels are the barely detectable 4–6 months of age postnatal.[19][20] High levels of testosterone will not appear again until the time of puberty.[5][21]