Androgen levels and sex functions in testosterone-treated hypogonadal men.

This study investigated the correlation of sex functions in testosterone-treated hypogonadal men and in tamoxifen-treated eugonadal men in relation to blood androgen levels. Self-reported sex functions in men treated with parenteral testosterone esters (levels fall very rapidly with this type of substitution therapy) declined at levels ranging between 11 and 5 nmole/L of testosterone. Although wide variations in individual responses were noted, levels of response in given individuals appeared to be reproducible. The critical level for oral testosterone undecanoate lies between 4 and 6 nmole/L testosterone, although the relatively high levels of dihydrotestosterone in testosterone undecanoate therapy probably produce an additive effect upon sex functions. Dihydrotestosterone is capable of maintaining sex functions in hypogonadal men. There is no evidence in this study design that androgen administration in excess of the individually determined critical levels further enhances sex functions. In view of the rapidly declining blood levels of androgens with the available parenteral testosterone ester preparations, the results suggest that hypogonadal patients may benefit from a more frequent administration of these preparations.