Relations between sex hormone level and characters of hair and skin in healthy young men

Hormonal regulation in male androgenetic alopecia-Sex hormones and beyond: Evidence from recent genetic studies

Male-pattern hair loss, also termed androgenetic alopecia (AGA), is a highly prevalent age-related condition that is characterized by a distinct pattern of hair loss from the frontotemporal and vertex regions of the scalp. The phenotype is highly heritable and hormone dependent, with androgens being the recognized critical hormonal factor. Numerous molecular genetic studies have focused on genetic variation in and around the gene that encodes the androgen receptor. More recently, however, the availability of high-throughput molecular genetic methods, novel methods of data analysis and sufficiently large sample sizes have rendered possible the systematic investigation of the contribution of other components of the androgen receptor pathway or hormonal pathways beyond the androgen receptor signalling pathways. Over the past decade, genome-wide association studies of increasingly large cohorts have enabled the genome-wide identification of genetic risk factors for AGA, and yielded unprecedented insights into the underlying pathobiology. The present review discusses some of the most intriguing genetic findings on the relevance of (sex)hormonal signalling in AGA.

A hypothetical pathogenesis model for androgenic alopecia: clarifying the dihydrotestosterone paradox and rate-limiting recovery factors

Androgenic alopecia, also known as pattern hair loss, is a chronic progressive condition that affects 80% of men and 50% of women throughout a lifetime. But despite its prevalence and extensive study, a coherent pathology model describing androgenic alopecia's precursors, biological step-processes, and physiological responses does not yet exist. While consensus is that androgenic alopecia is genetic and androgen-mediated by dihydrotestosterone, questions remain regarding dihydrotestosterone's exact role in androgenic alopecia onset. What causes dihydrotestosterone to increase in androgenic alopecia-prone tissues? By which mechanisms does dihydrotestosterone miniaturize androgenic alopecia-prone hair follicles? Why is dihydrotestosterone also associated with hair growth in secondary body and facial hair? Why does castration (which decreases androgen production by 95%) stop pattern hair loss, but not fully reverse it? Is there a relationship between dihydrotestosterone and tissue remodeling observed alongside androgenic alopecia onset? We review evidence supporting and challenging dihydrotestosterone's causal relationship with androgenic alopecia, then propose an evidence-based pathogenesis model that attempts to answer the above questions, account for additionally-suspected androgenic alopecia mediators, identify rate-limiting recovery factors, and elucidate better treatment targets. The hypothesis argues that: (1) chronic scalp tension transmitted from the galea aponeurotica induces an inflammatory response in androgenic alopecia-prone tissues; (2) dihydrotestosterone increases in androgenic alopecia-prone tissues as part of this inflammatory response; and (3) dihydrotestosterone does not directly miniaturize hair follicles. Rather, dihydrotestosterone is a co-mediator of tissue dermal sheath thickening, perifollicular fibrosis, and calcification - three chronic, progressive conditions concomitant with androgenic alopecia progression. These conditions remodel androgenic alopecia-prone tissues - restricting follicle growth space, oxygen, and nutrient supply - leading to the slow, persistent hair follicle miniaturization characterized in androgenic alopecia. If true, this hypothetical model explains the mechanisms by which dihydrotestosterone miniaturizes androgenic alopecia-prone hair follicles, describes a rationale for androgenic alopecia progression and patterning, makes sense of dihydrotestosterone's paradoxical role in hair loss and hair growth, and identifies targets to further improve androgenic alopecia recovery rates: fibrosis, calcification, and chronic scalp tension.

The Role of Facial and Body Hair Distribution in Women's Judgments of Men's Sexual Attractiveness

Facial and body hair are some of the most visually conspicuous and sexually dimorphic of all men's secondary sexual traits. Both are androgen dependent, requiring the conversion of testosterone into dihydrotestosterone via the enzyme 5α reductase 2 for their expression. While previous studies on the attractiveness of facial and body hair are equivocal, none have accounted as to how natural variation in their distribution may influence male sexual attractiveness. In the present study, we quantified men's facial and body hair distribution as either very light, light, medium, or heavy using natural photographs. We also tested whether women's fertility influenced their preferences for beards and body hair by comparing preferences among heterosexual women grouped according their fertility (high fertility, low fertility, and contraceptive use). Results showed that men with more evenly and continuously distributed facial hair from the lower jaw connecting to the mustache and covering the cheeks were judged as more sexually attractive than individuals with more patchy facial hair. Men with body hair were less attractive than when clean shaven, with the exception of images depicting some hair around the areolae, pectoral region, and the sternum that were significantly more attractive than clean-shaven bodies. However, there was no effect of fertility on women's preferences for men's beard or body hair distribution. These results suggest that the distribution of facial and body hair influences male attractiveness to women, possibly as an indication of masculine development and the synthesis of testosterone into dihydrotestosterone via 5α reductase.

Androgenic hormone profile in patients with androgenetic alopecia

In this article, the outcomes of the range of researches are described including the data on levels of testosterone, dihydrotestosterone, dehydroepiandrosterone sulfate, sex hormone-binding globulin and other components of androgen hormone profile in issues and biological fluids of males with androgenetic alopecia. Besides, in this article we describe results of recent studies devoted to effects of androgens on hair follicles and the role of 5-alpha reductase in conversion of androgens.

The value of middle phalangeal hair as an anthropometric marker: A review of the literature

Middle phalangeal hair (MPH) is a trait frequently examined in anthropological studies throughout the 20th century. MPH is found on the back of the middle segment of the fingers, excluding the thumb. Typically, researchers examined the presence and absence of hair in various populations, and described it in terms of age, ancestry, and sex. Recently MPH has been examined as a potential anthropometric indicator of: androgen levels, androgen-related side effects in women, gene homozygosity, and disease resistance. Given the potential value of this marker, the present paper provides a comprehensive overview of MPH and its associated characteristics (i.e., ethnicity, sex, age, and hormonal variations) and presents new data on the reliability of MPH assessment. Findings suggest that ethnicity, sex, and age need to be controlled in any studies examining MPH and its relationship with other variables. Two measures of MPH (i.e., presence/absence of MPH and actual hair count) are both acceptable to use in MPH assessment; and the use of a hand lens to examine MPH provides high reliability when MPH is assessed by expert raters. However, researchers should avoid participant self-assessment. Future avenues for research are suggested (e.g., measurement issues and studies on hormonal correlates in women). MPH could be useful in research or for clinical purposes as a possible non-invasive indicator of hormone levels or hormonal sensitivity, or of predisposition toward androgen-related or gene-homozygosity-related health issues or behaviors.

Clinical biochemistry of dihydrotestosterone

Dihydrotestosterone (DHT) is the most potent natural androgen in humans. There has been an increasing interest in this androgen and its role in the development of primary and secondary sexual characteristics as well as its potential roles in diseases ranging from prostate and breast cancer to Alzheimer's disease. Despite the range of pathologies shown to involve DHT there is little evidence for measurement of serum DHT in the management of these diseases. In this review we describe the physiology of DHT production and action, summarize current concepts in the role of DHT in the pathogenesis of various disorders of sexual development, compare current methods for the measurement of DHT and conclude on the clinical utility of DHT measurement. The clinical indications for the measurement of DHT in serum are: investigation of 5α reductase deficiency in infants with ambiguous genitalia and palpable gonads; men with delayed puberty and/or undescended testes; and to confirm the presence of active testicular tissue. Investigation is aided by the use of human chorionic gonadotrophin stimulation. Due to paucity of published data on this procedure, it is important to follow guidelines prescribed by the laboratory performing the analysis to ensure accurate interpretation.

Putting a finger on potential predictors of oral contraceptive side effects: 2D:4D and middle-phalangeal hair

Many women experience emotional or physical side effects when taking oral contraceptives (OCs). Despite the potential impact on women's health and well-being, there are no valid methods to screen women for their risk of OC side effects. The present paper presents the results of two studies where anthropometric indicators of androgen exposure, 2D:4D and middle-phalangeal hair, were examined for their potential as predictors of OC side effects. In study 1, 2D:4D was associated with women's reports of a history of: (a) negative mood side effects; (b) discontinuation due to negative mood side effects; (c) specific mood side effects (i.e., crying, sadness, and altered trust in one's partners) and (d) specific physical side effects (i.e., headaches, fatigue, and decreased sex drive). In study 2, 2D:4D and/or middle-phalangeal hair was/were associated with a reported history of: (a) discontinuation due to negative mood side effects; (b) specific mood-related side effects (i.e., negative mood, disrupted sleep, increased aggression, and altered trust in one's partner) and (c) specific physical side effects (i.e., headaches, decreased menstrual cramps, and increased sex drive/arousal). The general pattern was that adverse OC side effects were experienced by women with lower 2D:4D and fewer middle-phalangeal hairs. Almost all relationships remained significant when response bias was controlled. These results suggest a possible role for prenatal testosterone exposure and both androgen action and sensitivity in women's experience of OC side effects. Furthermore, these two digit measures may be useful predictors of hormonal contraceptive side effects in women.

Sex hormone levels and body hair growth in !Kung San and Kavango men from Namibia

The relation between hair growth and levels of sex hormones in serum and saliva was investigated in 256 !Kung San and Kavango men (ages 18 to 39 years) from Namibia/Southern Africa. Serum concentrations of total testosterone (Tser), 5 alpha-dihydrotestosterone (DHT), and estradiol (E2) as well as the level of bioavailable non-SHBG-bound testosterone in the saliva (Tsal) were determined by radioimmunoassay. The distribution and density of scalp and facial hair as well as the development of terminal hair on the chest, abdomen, pubic area, arms, fingers, and legs were categorized using objective criteria. Covariance analyses revealed marked differences in the distribution of body hair in the San and the Negro sample. This is partly explained by a significant influence of androgen and estrogen levels on the growth of terminal hair. DHT and the ratio DHT/Tser are significantly positively related to midphalangeal hair growth and negatively to pubic hair development. Tsal, the bioavailable fraction of total testosterone, exerts a weak positive influence on the degree of arm and leg hair growth; the most significant positive effect on the growth of abdominal, arm, and leg hair in our samples is caused by E2. The ratio Tser/E2 correlates significantly negatively with the arm and leg hair development and the ratio DHT/E2 with the degree of abdominal, pubic, arm, and leg hair, whereas lower DHT concentrations occur in men with stronger hair development.