Estradiol, the most important biologically active estrogen, has important functions in men . One of the most critical is its role in bone metabolism.
Men with aromatase deficiency or inactive estrogen receptor a develop severe osteoporosis. Most of the effects of T on bone depend on its aromatization into estradiol. Estradiol is also supposed to be the main active metabolite of T concerning its effects on the brain, though no significant sexual dysfunction was observed in men affected by congenital estrogen deficiency [258-260]. However in two men with aro-matase deficiency, Carani etal. observed a synergistic effect of estradiol and T on sexual behavior
In men about 20% of estradiol is formed in the Leydig cells, and the rest in peripheral tissues, especially fat cells, from aromatization of androgens— mainly T but also adrenal androstenedione . As a result, the estradiol level is higher in men with increased BMI, as well as in diabetic patients, while aromatization seems decreased by physical exercise . According to the studies there is no or only a slight decrease of serum estradiol with age, resulting in an increase in the estradiol/T ratio. However serum levels of free estradiol decrease because concentrations of SHBG, which binds estradiol, increase with age.
Animal experiments from Adaikan and co-workers show that any estrogen increase results in a reduction of circulating T levels (probably due to inhibition of the gonadotropic axis at the hypothalam-ic level, where estradiol is the active metabolite of T for its negative feedback action) and that the resulting estrogen/T imbalance precipitates ED in both rats
 and rabbits  by reducing intracavenosal pressure response to nerve stimulation, reducing relaxant response to acetylcholine and nitrergic transmission, and potentiating norepinephrine-induced anti-erectile contraction of corpora cavernosa
. Trichrome staining highlighted cavernosal connective tissue hyperplasia in the long-term study groups . These effects were observed following both estradiol and phytoestrogen administrations  leading to conjecture about the impact of exposure to environmental estrogens on male sexual function. One study of ED patients reported a high prevalence of exposure to pesticides, some of which have estrogenic or anti-androgenic properties, and an association between such an exposure and the severity of ED based on flat nocturnal erectile pattern was made . Mancini et al. also observed increased estradiol levels in a small group of ED
Continue reading here: Pregnenolone 17OH Pregnenolone
Was this article helpful?