China
Africa
Explore chapters and articles related to this topic
Geriatric hair and scalp disorders
Published in Robert A. Norman, Geriatric Dermatology, 2020
The pathophysiology of androgenetic alopecia in females is less well defined. In women, 50–60% of testosterone and dihydrotestosterone is produced by peripheral conversion of weaker androgens such as dehydroepiandrosterone. Sawaya and Price52 demonstrated consistent differences in hair follicles from young women and men with and without androgenetic alopecia. With reference to type II 5α-reductase, young females and males with androgenetic alopecia have higher levels of types I and II 5α-reductase in frontal hair follicles than occipital follicles. Androgen receptor content is 40% lower on the frontal scalp of females with androgenetic alopecia than males. Aromatase, responsible for converting testosterone and dihydrotestosterone back to estradiol, is six times more plentiful on female scalps. It is postulated that the higher levels of aromatase found in females may be responsible for the phenotypic differences and less severe expression of androgenetic alopecia in females52.
Effects on Human Males of In Utero Exposure to Exogenous Sex Hormones
Published in Takao Mori, Hiroshi Nagasawa, Toxicity of Hormones in Perinatal Life, 2020
The third mechanism of DES antagonism of testicular androgens in the developing male fetus is directly on the target organs. The target organs are the accessory or secondary sexual organs which are the epididymis, vas deferens, seminal vesicles, prostate, urethra, penis, and scrotum. Liao and Fang77 reported that DES competed with 5α-dihydrotestosterone for 5α-dihydrotestosterone nuclear receptor at concentrations of 10 to 50 Mil rodent prostates. Rennie and Bruchovsky78 and Bellis et al.79 have extensively studied the competitive binding of androgen and estrogen binding to target organ epithelium and muscle in both in vivo and in vitro studies. Lasnitzki80 demonstrated estrogen antagonism of androgens on prostatic epithelium in organ culture. Several groups (Baulieu and Robel,81 Shimazaki et al.,82 and Lee et al.83) have studied the direct inhibition of estrogens on the enzyme 5α-reductase which is necessary to convert testosterone to the more active dihydrotestosterone in certain target organs (prostate, urethra, penis).
Mechanism of Action of Isotretinoin
Published in Ayse Serap Karadag, Berna Aksoy, Lawrence Charles Parish, Retinoids in Dermatology, 2019
FoxO1 also binds directly to the POMC promoter and negatively regulates its transcription. In addition, FoxO3a interacts with STAT3 and inhibits POMC promoter activity (52,53). Isotretinoin-induced upregulation of FoxO1 and FoxO3a may thus explain isotretinoin-mediated suppression of POMC-dependent pituitary gene expression, the precursor of ACTH. Isotretinoin-mediated upregulation of p53 attenuates androgen receptor (AR) gene expression (54). p53 and FoxO1 suppress AR expression and transactivation, respectively (55,56). This has been demonstrated in the skin of isotretinoin-treated acne patients, where isotretinoin has reduced AR expression as well as 5α-reductase activity in the skin, which has lost 80% of their ability to form 5α-dihydrotestosterone (57,58). In contrast, p53 deletion has activated AR signaling and restored c-MYC-induced differentiation in sebaceous glands (59). p53 is a negative regulator of thyroid hormone receptor-signaling pathways (60).
Microneedle mediated transdermal delivery of β-sitosterol loaded nanostructured lipid nanoparticles for androgenic alopecia
Published in Drug Delivery, 2022
Kousalya Prabahar, Ubaidulla Udhumansha, Nehal Elsherbiny, Mona Qushawy
Alopecia is the partial or total reduction of hair in a specific area of the skin that affects millions of men and women worldwide (Pereira et al., 2018). Alopecia affects 50% and 40% of adult male and female respectively, and the percentage is increasing by nearly 5% every year (Ashique et al., 2020). Androgenetic alopecia has been linked to higher levels of dihydrotestosterone (DHT) in balding scalp follicles than in non-balding ones. Hair loss is caused by an increase in the concentrations of 5α-reductase and androgen receptors. Androgenetic alopecia was first treated with finasteride, a 5-hydroxysteroid reductase inhibitor, which was approved by the FDA to be used in the handling of alopecia. As a result, it can cause impotence and other sexual dysfunctions as well as testicular pain and myalgia (Jain et al., 2015). Therefore, development of alternative safe and effective therapeutic strategies is of great demand. Natural products have been widely used to treat androgenic alopecia (AGA) due to their safety with less or no toxic effects.
To What Extent are Prenatal Androgens Involved in the Development of Male Homosexuality in Humans?
Published in Journal of Homosexuality, 2022
Although hirsutism and mesomorphism are typically associated with adult, rather than prenatal, androgen levels, they may also be hinting at a relationship between male homosexuality and elevated 5α-reductase activity. 5α-reductase converts testosterone to dihydrotestosterone (DHT), a more potent androgen regulating body hair growth and male genital development, but not musculature. If 5α-reductase activity is elevated, then more testosterone will be converted to DHT, leading to a smaller musculature (due to the reduced circulating testosterone), increased hirsutism, and larger genital size, as well as potential effects on brain development during gestation. A finding by Doerr, Pirke, Kockott, and Dittmar (1976) that the ratio of circulating DHT/testosterone levels was higher in gay than straight men in adulthood supports this theory. Bogaert and Hershberger (1999) also found in a sample of 5,122 men that gay men had significantly larger and thicker penises than straight men. However, those results were self-reported and subjects may have inflated their own measurements, thus potentially introducing bias. The experiment by Alias also fails to analyze factors such as exercise levels and hair removal, while ethnicity, a significant confounder, and the methods of subject recruitment and sexual orientation evaluation are not clearly outlined.
Homeostasis: apoptosis and cell cycle in normal and pathological prostate
Published in The Aging Male, 2020
Norelia Torrealba, Gonzalo Rodríguez-Berriguete, Raúl Vera, Benito Fraile, Gabriel Olmedilla, Pilar Martínez-Onsurbe, Manuel Sánchez-Chapado, Ricardo Paniagua, Mar Royuela
Prostate cancer is the second most prevalent cancer in men worldwide. Likewise, most men will develop benign prostatic hyperplasia (BPH) around the age of 60. Both pathologies develop in a different anatomical area. BPH appears in the transition zone of the gland while prostate cancer develops from epithelial cells located in the peripheral zone of the prostate gland along with a small percentage that arises from those cells that are in the transition zone. However, in 20% of the cases, BPH and cancer coexist in the same prostatic area [1]. We can define the BPH as a noncancerous increase in size of the prostate, perhaps due to the influence of cytokines [2–4]. To alleviate the most significant symptoms, different treatments have been used, including the use of alpha-blocking inhibitors of 5α-reductase, such as finasteride or dutasteride, which have different efficacy [5]. In the last time, nucleotide polymorphisms are significantly associated with the efficacy of BPH treatment [6]. Prostate cancer is related to many factors. Among them, there would be factors as different as cytokines [7], human papillomavirus [8], or even nutrition. In this sense, some recent works relate the importance of a good diet may lower the risk of prostate cancer [9–11].