Basic Intracellular Mechanism of
Action of Testosterone
Most of the effects of testosterone result basically from increased
rate of protein formation in the target cells. This has been studied
extensively in the prostate gland, one of the organs that is most affected by
testos-terone. In this gland, testosterone enters the prostatic cells within a
few minutes after secretion. Then it is most often converted, under the
influence of the intracellular enzyme 5a-reductase,
to dihydrotestos-terone, and this in
turn binds with a cytoplasmic “receptor protein.” This combination migrates to
the cell nucleus, where it binds with a nuclear protein and induces DNA-RNA
transcription. Within 30 minutes, RNA polymerase has become activated and the
con-centration of RNA begins to increase in the prostatic cells; this is
followed by progressive increase in cellu-lar protein. After several days, the
quantity of DNA in the prostate gland has also increased and there has been a
simultaneous increase in the number of prostatic cells.
Testosterone stimulates production of proteins virtually everywhere
in the body, although more specifically affecting those proteins in “target”
organs or tissues responsible for the development of both primary and secondary
male sexual characteristics.
Recent studies suggest that testosterone, like other steroidal
hormones, may also exert some rapid, non-genomic effects that do not require
synthesis of new proteins. The physiological role of these nongenomic actions
of testosterone, however, has yet to be determined.