In women the major circulating androgen precursors and bioactive androgens, in descending order of serum concentrations, are dehydroepiandrosterone sulphate (DHEAS), dehydroepiandrosterone (DHEA), androstenedione (A4), T and dihydrotestosterone (DHT) (Davison & Davis 2003). T and DHT are the only potent bioactive androgens that bind directly to the AR, while DHEAS, DHEA and A4 are pro-androgens which require conversion to T and/or DHT to exert androgenic effects (Burger 2002). In females, T and DHT are predominantly formed by peripheral conversion (in liver, adipose tissue and skin) of androgen precursors that are secreted from the adrenal glands and the ovaries. DHEA and DHEAS are largely derived from the adrenal glands (Abraham 1974), while T, DHT and A4 levels originate equally from the ovary and adrenals (Davison & Davis 2003). In the ovary androgen synthesis favours the ∆ ۵ -pathway (Figure 1), which involves the conversion of cholesterol to pregnenolone by the enzyme P450 side chain cleavage (P450scc, CYP11A1). Pregnenolone is then metabolized to DHEA by P450c17 (CYP17A1) and then A4 by 3βHSD. A4 can then be converted to the bioactive androgen T by 17βHSD. Subsequently, T can then either be aromatized into oestradiol (E2) by P450arom (CYP19) or educed to DHT by 5α-Reductase 1 (SRD5A1) or 2 (SRD5A2). DHT can be enzymatically reduced into 5α-androstanediols, reversibly into 3α-diol and irreversibly to 3β-diol (Longcope 1986; Miller & Auchus 2011). The production of androgens within the ovarian follicle is under the control of luteinizing hormone (LH), with LH acting via LH receptors on theca cells to stimulate the rate-limiting conversion of cholesterol to pregnenolone (Longcope 1986; Erickson et al. 1985). Within the ovarian follicle, androgen synthesis and then the subsequent conversion of androgens to estrogens is compartmentalized in a cell-specific manner, known as the two-cell, two gonadotrophin hypothesis (Hillier et al. 1994). A4 and T are synthesized in the theca cells, before being diffused into the granulosa cells where they are converted into oestrone (E1) or E2, respectively (Ghayee & Auchus 2007; Burger 2002).