Dr. Ron’s Research Review – May 18, 2016

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This week’s research review focuses on estrogen and male sexuality.

Traditionally, testosterone and estrogen have been considered to be male and female sex hormones. However, estradiol is essential for modulating libido, erectile function, and spermatogenesis. Estrogen receptors and aromatase are abundant in brain, penis, and testis. In the brain, estradiol synthesis is increased in areas related to sexual arousal. In the penis, estrogen receptors are found throughout the corpus cavernosum with high concentration around neurovascular bundles. Low testosterone and elevated estrogen increase the incidence of erectile dysfunction independently of one another. In the testes, spermatogenesis is modulated at every level by estrogen, starting with the hypothalamus-pituitary-gonadal axis, followed by the Leydig, Sertoli, and germ cells, and finishing with the ductal epithelium, epididymis, and mature sperm. Regulation of testicular cells by estradiol shows both an inhibitory and a stimulatory influence, indicating an intricate symphony of dose-dependent and temporally sensitive modulation. (Schulster et al., 2016)

Administration of testosterone concurrently with aromatase inhibitors markedly impaired sexual functioning. In men with serum testosterone <300 ng dl−1, libido was significantly improved when estradiol levels were >5 ng dl−1 It thus appears that both estrogen and testosterone are necessary for libido in hypogonadal men. Estrogenic excess from the peripheral aromatization of adipose tissue can also lead to a direct inhibitory effect of pituitary function and, thus, impaired spermatogenesis. Aromatase inhibitors, such as Arimidex, are primarily used in patients with a testosterone to estradiol ratio <10:1 to increase testosterone production and spermatogenesis. (Smith et al., 2016)

Dr. Ron


 

Articles

The role of estradiol in male reproductive function.
            (Schulster et al., 2016) Download
Traditionally, testosterone and estrogen have been considered to be male and female sex hormones, respectively. However, estradiol, the predominant form of estrogen, also plays a critical role in male sexual function. Estradiol in men is essential for modulating libido, erectile function, and spermatogenesis. Estrogen receptors, as well as aromatase, the enzyme that converts testosterone to estrogen, are abundant in brain, penis, and testis, organs important for sexual function. In the brain, estradiol synthesis is increased in areas related to sexual arousal. In addition, in the penis, estrogen receptors are found throughout the corpus cavernosum with high concentration around neurovascular bundles. Low testosterone and elevated estrogen increase the incidence of erectile dysfunction independently of one another. In the testes, spermatogenesis is modulated at every level by estrogen, starting with the hypothalamus-pituitary-gonadal axis, followed by the Leydig, Sertoli, and germ cells, and finishing with the ductal epithelium, epididymis, and mature sperm. Regulation of testicular cells by estradiol shows both an inhibitory and a stimulatory influence, indicating an intricate symphony of dose-dependent and temporally sensitive modulation. Our goal in this review is to elucidate the overall contribution of estradiol to male sexual function by looking at the hormone's effects on erectile function, spermatogenesis, and libido.

Estradiol exerts alterations in sexual function and fertility in human males.
            (Smith et al., 2016) Download
A recent study by Finkelstein et al.4 found that administration of testosterone concurrently with aromatase inhibitors markedly impaired sexual functioning. Similarly, Ramasamy et al.5 posed a compelling argument by demonstrating that in men with serum testosterone <300 ng dl−1, libido was significantly improved when estradiol levels were >5 ng dl−1 It thus appears that both estrogen and testosterone are necessary for libido in hypogonadal men. Estrogenic excess from the peripheral aromatization of adipose tissue can also lead to a direct inhibitory effect of pituitary function and, thus, impaired spermatogenesis. Aromatase inhibitors, such as Arimidex, are primarily used in patients with a testosterone to estradiol ratio <10:1 to increase testosterone production and spermatogenesis.

 


References

Schulster, M, AM Bernie, and R Ramasamy (2016), ‘The role of estradiol in male reproductive function.’, Asian J Androl, PubMed: 26908066
Smith, RP, LI Lipshultz, and JR Kovac (2016), ‘Estradiol exerts alterations in sexual function and fertility in human males.’, Asian J Androl, PubMed: 27048785