Fig. 1.

Schematic overview of C₁₉steroid biosynthesis, intracrine action, metabolism and urinary excretion. Yellow balls represent the androgen sulfate, blue balls the glucuronide. After metabolic activation the androgen binds the androgen receptor (red) and the complex translocates into the nucleus (grey) to work as transcription factor. It should be noted that while intracrine pathways play the major role for peripheral androgen action, active androgens such as T are produced by the testes and the adrenal, albeit only low levels, and these do not require activation in target tissue. CYP, cytochrome P450; HSD, hydroxysteroid dehydrogenase; SHBG, sex hormone binding globulin; STS, steroid sulfatase; SULT, sulfotransferase.