SERUM PREGNENOLONE, PROGESTERONE, 17α-HYDROXYPROGESTERONE, ANDROSTENEDIONE, TESTOSTERONE, 5α-DIHYDROTESTOSTERONE AND ANDROSTERONE DURING PUBERTY IN BOYS

We have determined the concentrations of pregnenolone, progesterone, 17α-hydroxyprogesterone, androstenedione, testosterone, 5α-dihydrotestosler-one and androsterone in serum samples collected from a total of seventy-nine boys who were 8–18 years of age at the time the first blood samples were drawn. Additional samples were drawn from sixty-six and forty-four of these boys after 1 and 2 year intervals, respectively. The first increases in serum steroid concentrations were those of androstenedione and androsterone, thus supporting the hypothesis that an early activation of the adrenal cortex is the first hormonal change in puberty. This increase in serum androstenedione occurred 2 years earlier than the first significant increase in serum testosterone, which took place by 13 5 years, after the first signs of external genital development, but in concert with the onset of pubic hair growth. The serum concentrations of 5α-dihydrotestosterone were closely related to those of testosterone, but the relative increases were smaller, the consequence of which is a decrease in the ratio of 5α-dihydrotestosterone: testosterone throughout puberty. The main increase in serum androsterone tends to take place after that of 5α-dihydrotestosterone and testosterone. In comparison with the four androgens, the serum concentrations of their C₂₁ precursors correlated rather poorly with the physical signs of advancing puberty. As in the case of androstenedione, the concentrations of pregnenolone and 17α-hydroxyprogesterone were relatively high in the youngest age groups, which probably also reflects an early adrenal activation. In contrast to testosterone, the major increases in precursor steroids occur at a relatively late stage of puberty. It seems likely therefore that a major qualitative shift in the testicular secretion of steroids occurs during puberty in boys.