Role of oestrogen in male sexual behaviour: insights from the natural model of aromatase deficiency

OBJECTIVE In order to evaluate the role of oestrogens on human male sexual behaviour, the gender-identity, psychosexual orientation and sexual activity of a man with a congenital lack of oestradiol resulting from an inactivating mutation of the aromatase P450 gene was investigated. The psychosexual and sexual behavioural evaluations were performed before and during testosterone treatment and before oestradiol treatment, during three phases of different dosages of oestradiol treatment. DESIGN The study was performed before (phase A) and during (phase B) testosterone enanthate treatment (250 mg i.m, every 10 days, for 6 months), during testosterone withdrawal (phase C), and during each of the following transdermal oestradiol treatments: 50 mu g twice a week for 6 months (phase D); 25 mu g twice a week for 9 months (phase E), and 12.5 mu g twice a week for 9 months (phase F). MEASUREMENTS Sexual behaviour was investigated by a sexological interview and by a 2-month self-reported daily diary performed during each phase of the protocol study. Furthermore, during each oestradiol treatment (phase C, D, E and F), a study of depression, anxiety trait and sexual behaviour was performed by the Beck Depression Inventory (BDI), the Spielberger Trait Anxiety Inventory (STAI) and the Golombok-Rust Inventory of Sexual Satisfaction (GRISS), respectively. Sexual orientation and gender-identity were evaluated by the BEM Sex Role Inventory (BSRI), Serum testosterone and oestradiol were measured during each phase of the study. RESULTS Before oestradiol treatment (phase C), serum oestradiol was undetectable, while it rose to 356.1, 88.1 and 55.1 pmol/l during phases D, E and F, respectively. Before any oestradiol treatment, during phase D, phase E and phase F serum testosterone was 18.13, 0.72, 14.3 and 18.51 nmol/l, respectively. The patient's gender-identity as assessed by BSRI and by the sexological interview was clearly male. The psychosexual orientation evaluated by BSRI, by the sexological interview and by the analysis of the self-filled diary was heterosexual. Relevant modification of the patient's sexual behaviour occurred only during oestrogen treatment. This was more evident during both phase E and phase F, and concerned the behavioural parameters with an increase of libido, frequency of sexual intercourse, masturbation and erotic fantasies. A reduction of BDI and STAI scores was detected during the oestrogen phases. CONCLUSIONS The study of the sexual behaviour in this man with aromatase deficiency suggests that oestrogens in humans do not affect gender-identity and sexual orientation but could have a role in male sexual activity.