Immunohistochemical localization of types 1 and 2 5alpha-reductase in human scalp

Discovery of (2S)-N-(6-Cyano-5-(trifluoromethyl)pyridin-3-yl)-3-(6-(4-cyanophenyl)-3,6-diazabicyclo[3.1.1]heptan-3-yl)-2-hydroxy-2-methylpropanamide as a Highly Potent and Selective Topical Androgen Receptor Antagonist for Androgenetic Alopecia Treatment

Androgenetic alopecia (AGA) is the most prevalent form of progressive hair loss disorder in both men and women, significantly impacting their appearance and overall quality of life. Overactivation of the AR signaling pathway in dermal papilla cells (DPCs) plays a crucial role in the development and progression of AGA. Considering the severe systemic side effects associated with oral AR antagonists, the idea of developing of topical AR antagonists with rapid metabolic deactivation properties emerged as a promising approach. Herein, through systematic structural optimization, we successfully identified compound 30a as a potent and selective AR antagonist with favorable pharmacokinetic properties, resulting in high skin exposure and low plasma exposure following topical administration. Importantly, in both hair-growth and AGA mouse models, compound 30a showed potent hair-growth-promoting effects without any noticeable toxicity. These findings suggest that compound 30a holds significant potential as a topical AR antagonist for treating AGA patients.

Exploring the effects of Chinese herbal ingredients on the signaling pathway of alopecia and the screening of effective Chinese herbal compounds

ETHNOPHARMACOLOGICAL RELEVANCE

alopecia is a hair disorder that can add a significant medical and psychological burden to patients. Currently, the FDA-approved drugs for the treatment of androgenetic alopecia (AGA) are minoxidil and finasteride and immunosuppressives are therapeutic options for alopecia areata (AA), but the objective adverse effects and high cost of these treatments reduce patient compliance and thus the effectiveness of the drugs. Traditional Chinese medicine (TCM) has good efficacy, a high safety profile and low treatment costs, but its mechanism of action is still not fully understood. The use of signaling pathways to modulate hair loss is a major direction in the study of the pathogenesis and pharmacology of alopecia.

AIM OF THE STUDY

This review aims to collect the results of experimental studies related to alopecia, to screen previously documented combinations of herbs claimed to be effective based on the herbs and their constituent compounds used in the identified studies, and to uncover other useful information that we hope will better guide the clinical application and scientific research of drug combinations or individual herbs for the treatment of alopecia.

MATERIALS AND METHODS

We have reviewed experimental studies to determine the methods used and the mechanisms of action of the herbs and constituent compounds. The following keywords were searched in databases, including PubMed, EMBASE, CNKI and CSTJ." Medicinal plants" "Chinese herbal medicine", "hair loss", " alopecia", "androgenetic alopecia" and " alopecia areata ". We also collected combinations of drugs from books approved by various schools for screening.

RESULTS

Using known combinations of compounds within herbal medicine to match the documented combinations, 34 topical combinations and 74 oral combinations were identified, and among the 108 herbal combinations screened Angelica, Rehmannia glutinosaLigusticum chuanxiong hort, Radix Rehmanniae, etc. The number of occurrences was very high, and the association with vascular drugs was also found to be very close.

CONCLUSIONS

This review further elucidates the therapeutic mechanisms of the compounds within the herbal components associated with alopecia and screens for other combinations that may be dominated by this component for the treatment of alopecia, uncovering compounds from other drugs that may be key factors in the treatment of alopecia. This improvement will provide a better quality of evidence for the effectiveness of herbs and compounds used to treat alopecia.

Development and Qualification of a Physiologically Based Pharmacokinetic Model of Finasteride and Minoxidil Following Scalp Application

In this study, we aimed to develop and qualify a PBPK model for scalp application using two drugs with marked differences in physicochemical properties and PK profiles. The parameters related to scalp physiology, drug PK, and formulations were incorporated into a Multi-Phase and Multi-Layer (MPML) Mechanistic Dermal Absorption (MechDermA) model within the Simcyp® Simulator V17. The finasteride PBPK model was linked to its effect on dihydrotestosterone (DHT) levels in plasma and scalp using an indirect response model. Predicted PK (and PD for finasteride) profiles and parameters were compared against the clinically reported data and justified by visual predictive checks and two-fold error criteria for model verification. The PBPK/PD model for finasteride reasonably demonstrated an ability to predict its respective PK and PD profiles, and parameters following scalp application under various clinical scenarios. Using the same scalp physiological input parameters, the minoxidil PBPK model was then developed and satisfactorily qualified with independent clinical datasets. Collectively, these results suggested that the established PBPK model may have broader utility for other topical formulations intended for scalp application.

Understanding Hormonal Therapies: Overview for the Dermatologist Focused on Hair

Hormones have an intimate relationship with hair growth. Hormonal replacement therapy is used to treat menopausal symptoms and to provide protection from chronic diseases for which postmenopausal women may be at risk. Additionally, hormonal therapies are prescribed for contraception and treatment of acne. Considering the widespread use of such therapies, there is a demand for further understanding of their implications in hair disorders. This article reviews the specific properties of current estrogen- and progesterone-containing hormonal treatments and their implications for the patient with hair loss. The complexity of the task comes from the paucity of data and discrepancy in the literature on the effect of the specific hormonal-receptor activities.

Pharmacological therapeutics in androgenetic alopecia

Androgenetic alopecia (AGA) is the most common type of hair loss and affects both men and women. Male pattern hair loss shows characteristic frontal recession and vertex baldness, whereas female pattern hair loss produces diffuse alopecia over the mid-frontal scalp. AGA is mediated by increased androgen susceptibility in affected scalp hairs. 5α-Reductase converts testosterone into dihydrotestosterone, a potent androgen, in the scalp. Both androgen receptors and 5α-reductase have higher expression levels in the balding scalp than in non-affected regions. Increased androgen susceptibility induces hair follicle miniaturization, which leads to the progressive loss of thicker terminal hairs in the balding scalp. Currently, topical minoxidil and oral 5α-reductase inhibitors, such as finasteride and dutasteride, are approved options for the pharmacological treatment of AGA. Topical minoxidil remains the mainstay of therapy for mild to moderate AGA in both men and women. The daily intake of 1-mg finasteride or 0.5-mg dutasteride shows better efficacy than topical minoxidil in regard to hair regrowth in male AGA. Anti-androgens can be used in female AGA wit clinical and biochemical evidence of hyperandrogenism. Patients may be overwhelmed and confused by the variety of treatment options for AGA management, including over-the-count drugs with low evidence quality. Therefore, physicians must be aware of the current guidelines for the management of AGA based on evidence-based approaches to select better options for patients.

Consequences of steroid-5α-reductase deficiency and inhibition in vertebrates

In 1974, a lack of 5α-dihydrotestosterone (5α-DHT), the most potent androgen across species except for fish, was shown to be the origin of a type of pseudohermaphrodism in which boys have female-like external genitalia. This human intersex condition is linked to a mutation in the steroid-5α-reductase type 2 (SRD5α2) gene, which usually produces an important enzyme capable of reducing the Δ⁴-ene of steroid C-19 and C-21 into a 5α-stereoisomer. Seeing the potential of SRD5α2 as a target for androgen synthesis, pharmaceutical companies developed 5α-reductase inhibitors (5ARIs), such as finasteride (FIN) and dutasteride (DUT) to target SRD5α2 in benign prostatic hyperplasia and androgenic alopecia. In addition to human treatment, the development of 5ARIs also enabled further research of SRD5α functions. Therefore, this review details the morphological, physiological, and molecular effects of the lack of SRD5α activity induced by both SRD5α mutations and inhibitor exposures across species. More specifically, data highlights 1) the role of 5α-DHT in the development of male secondary sexual organs in vertebrates and sex determination in non-mammalian vertebrates, 2) the role of SRD5α1 in the synthesis of the neurosteroid allopregnanolone (ALLO) and 5α-androstane-3α,17β-diol (3α-diol), which are involved in anxiety and sexual behavior, respectively, and 3) the role of SRD5α3 in N-glycosylation. This review also features the lesser known functions of SRD5αs in steroid degradation in the uterus during pregnancy and glucocorticoid clearance in the liver. Additionally, the review describes the regulation of SRD5αs by the receptors of androgens, progesterone, estrogen, and thyroid hormones, as well as their differential DNA methylation. Factors known to be involved in their differential methylation are age, inflammation, and mental stimulation. Overall, this review helps shed light on the various essential functions of SRD5αs across species.

Frontal fibrosing alopecia: efficacy of treatment modalities

Frontal fibrosing alopecia (FFA) is a primary cicatricial alopecia characterized by loss of follicular stem cells, fibrosis, and a receding frontotemporal hairline, with frequent loss of eyebrows, and less commonly, body hair involvement. Diagnosis is clinical and the disease most often affects postmenopausal women. Treatment is difficult with the goal of disease stabilization rather than hair regrowth due to the scarring nature of FFA. To date, there are no randomized controlled trials evaluating efficacy of treatments. Therefore, much of our knowledge is based on small retrospective studies. In this review, we highlight the various and most current treatment options for FFA, including 5-α-reductase inhibitors, intralesional steroids, hydroxychloroquine, topical steroids, topical calcineurin inhibitors, systemic retinoids, pioglitazone, oral antibiotics, minoxidil, excimer laser, and hair transplantation. Currently, 5-α-reductase inhibitors, intralesional steroids, and hydroxychloroquine have the highest level of evidence for treating FFA, while the remaining therapies have variable results and require further data to draw definitive conclusions.

Serum Levels of Androgen-Associated Hormones Are Correlated with Curative Effect in Androgenic Alopecia in Young Men

Background

Androgenic alopecia (AGA) is the most common type of hair loss in men. However, the pathogenesis is not yet fully understood and therapeutic approaches are limited. This retrospective study investigated the association between levels of androgen-associated hormones and curative effect in androgenic alopecia in young male AGA patients.

Material/Methods

By using chemiluminescence immunoassay, serum levels of androgens and upstream regulated hormones were measured in 178 young male patients with AGA and in 61 normal controls before therapy, 1 and 2 weeks after administration of finasteride.

Results

Before oral finasteride therapy, we found significantly higher levels of serum free testosterone (FT) and dihydrotestosterone (DHT) in AGA patients than in normal controls. The levels of serum sex hormone-binding globulin (SHBG), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) were similar in the 2 groups. There were no significant differences in serum androgen levels, including DHT and FT, among AGA patients with different grades of hair loss severity (p>0.05). After finasteride therapy, the levels of DHT decreased significantly (p<0.05). Increased serum levels of LSH or LH were also observed in 55 patients after therapy (p<0.05). The levels of SHGB did not change significantly after therapy (p>0.05). Patients with lower levels of serum FT and DHT than before who accepted finasteride therapy had a higher ratio of curative effect manifested by improved severity grade (p<0.05). Patients with higher levels of LSH or LH had a lower curative rate compared to those without change after therapy (p<0.05).

Conclusions

We confirmed the role of the androgens hypothalamus-hypophysis-sexual gland axis in the pathogenesis of AGA and the treatment effect of oral anti-androgen therapy in young male Chinese patients.

Circulating and intraprostatic sex steroid hormonal profiles in relation to male pattern baldness and chest hair density among men diagnosed with localized prostate cancers

BACKGROUND

Prospective cohort studies of circulating sex steroid hormones and prostate cancer risk have not provided a consistent association, despite evidence from animal and clinical studies. However, studies using male pattern baldness as a proxy of early-life or cumulative androgen exposure have reported significant associations with aggressive and fatal prostate cancer risk. Given that androgens underlie the development of patterned hair loss and chest hair, we assessed whether these two dermatological characteristics were associated with circulating and intraprostatic concentrations of sex steroid hormones among men diagnosed with localized prostate cancer.

METHODS

We included 248 prostate cancer patients from the NCI Prostate Tissue Study, who answered surveys and provided a pre-treatment blood sample as well as fresh frozen adjacent normal prostate tissue. Male pattern baldness and chest hair density were assessed by trained nurses before surgery. General linear models estimated geometric means and 95% confidence intervals (95%CIs) of each hormone variable by dermatological phenotype with adjustment for potential confounding variables. Subgroup analyses were performed by Gleason score (<7 vs ≥7) and race (European American vs. African American).

RESULTS

We found strong positive associations of balding status with serum testosterone, dihydrotestosterone (DHT), estradiol, and sex hormone-binding globulin (SHBG), and a weak association with elevated intraprostatic testosterone. Conversely, neither circulating nor intraprostatic sex hormones were statistically significantly associated with chest hair density. Age-adjusted correlation between binary balding status and three-level chest hair density was weak (r = 0.05). There was little evidence to suggest that Gleason score or race modified these associations.

CONCLUSIONS

This study provides evidence that balding status assessed at a mean age of 60 years may serve as a clinical marker for circulating sex hormone concentrations. The weak-to-null associations between balding status and intraprostatic sex hormones reaffirm differences in organ-specific sex hormone metabolism, implying that other sex steroid hormone-related factors (eg, androgen receptor) play important roles in organ-specific androgenic actions, and that other overlapping pathways may be involved in associations between the two complex conditions.

Effect of 5α-Reductase Inhibitors on Sexual Function: A Meta-Analysis and Systematic Review of Randomized Controlled Trials

INTRODUCTION

5α-Reductase inhibitors (5ARIs) are widely used for the treatment of benign prostatic hyperplasia (BPH) and androgenetic alopecia (AGA).

AIM

To review all the available data on the effect of 5ARIs on sexual function and assess whether 5ARIs increase the risk of sexual dysfunction.

METHODS

A systematic search of the literature was conducted using the Medline, Embase, and Cochrane databases. The search was limited to articles published in English and up to October 2015. Article selection proceeded according to the search strategy based on Preferred Reporting Items for Systematic Reviews and Meta-analyses criteria. Data were analyzed using Stata 12.0. A fixed- or a random-effects model was used to calculate the overall combined risk estimates. Publication bias was assessed using Begg and Egger tests.

MAIN OUTCOME MEASURES

Sexual dysfunction, erectile dysfunction, and decreased libido.

RESULTS

After screening 493 articles, 17 randomized controlled trials with 17,494 patients were included. Nine studies evaluated the efficacy of 5ARIs in men with BPH. The other eight reported using 5ARIs in the treatment of men with AGA. The mean age of participants was 60.10 years across all studies. We included 10 trials (6,779 patients) on the efficacy and safety of finasteride, 4 trials (6,222 patients) on the safety and tolerability of dutasteride, and 3 trials (4,493 patients) using finasteride and dutasteride for AGA. The pooled relative risks for sexual dysfunction were 2.56 (95% CI = 1.48-4.42) in men with BPH and 1.21 (95% CI = 0.85-1.72) in men with AGA; those for erectile dysfunction were 1.55 (95% CI = 1.14-2.12) in men with BPH and 0.66 (95% CI = 0.20-2.25) in men with AGA; and those for decreased libido were 1.69 (95% CI = 1.03-2.79) in men with BPH and 1.16 (95% CI = 0.50-2.72) in men with AGA. Estimates of the total effects were generally consistent with the sensitivity analysis. No evidence of publication bias was observed.

CONCLUSION

Evidence from the randomized controlled trials suggested that 5ARIs were associated with increased adverse effects on sexual function in men with BPH compared with placebo. However, the association was not statistically significant in men with AGA. Well-designed randomized controlled trials are indicated to study further the mechanism and effects of 5ARIs on sexual function.

Identification of a new plant extract for androgenic alopecia treatment using a non-radioactive human hair dermal papilla cell-based assay

BACKGROUND

Androgenic alopecia (AGA) is a major type of human scalp hair loss, which is caused by two androgens: testosterone (T) and 5α-dihydrotestosterone (5α-DHT). Both androgens bind to the androgen receptor (AR) and induce androgen-sensitive genes within the human hair dermal papilla cells (HHDPCs), but 5α-DHT exhibits much higher binding affinity and potency than T does in inducing the involved androgen-sensitive genes. Changes in the induction of androgen-sensitive genes during AGA are caused by the over-production of 5α-DHT by the 5α-reductase (5α-R) enzyme; therefore, one possible method to treat AGA is to inhibit this enzymatic reaction.

METHODS

RT-PCR was used to identify the presence of the 5α-R and AR within HHDPCs. A newly developed AGA-relevant HHDPC-based assay combined with non-radioactive thin layer chromatography (TLC) detection was used for screening crude plant extracts for the identification of new 5α-R inhibitors.

RESULTS

HHDPCs expressed both 5α-R type 1 isoform of the enzyme (5α-R1) and AR in all of the passages used in this study. Among the thirty tested extracts, Avicennia marina (AM) displayed the highest inhibitory activity at the final concentration of 10 μg/ml, as the production of 5α-DHT decreased by 52% (IC50 = 9.21 ± 0.38 μg/ml).

CONCLUSIONS

Avicennia marina (AM) was identified as a potential candidate for the treatment of AGA based on its 5α-R1-inhibitory activity.

Minoxidil may suppress androgen receptor-related functions

Although minoxidil has been used for more than two decades to treat androgenetic alopecia (AGA), an androgen-androgen receptor (AR) pathway-dominant disease, its precise mechanism of action remains elusive. We hypothesized that minoxidil may influence the AR or its downstream signaling. These tests revealed that minoxidil suppressed AR-related functions, decreasing AR transcriptional activity in reporter assays, reducing expression of AR targets at the protein level, and suppressing AR-positive LNCaP cell growth. Dissecting the underlying mechanisms, we found that minoxidil interfered with AR-peptide, AR-coregulator, and AR N/C-terminal interactions, as well as AR protein stability. Furthermore, a crystallographic analysis using the AR ligand-binding domain (LBD) revealed direct binding of minoxidil to the AR in a minoxidil-AR-LBD co-crystal model, and surface plasmon resonance assays demonstrated that minoxidil directly bound the AR with a K_d value of 2.6 μM. Minoxidil also suppressed AR-responsive reporter activity and decreased AR protein stability in human hair dermal papilla cells. The current findings provide evidence that minoxidil could be used to treat both cancer and age-related disease, and open a new avenue for applications of minoxidil in treating androgen-AR pathway-related diseases.

Assessment of the usefulness of dihydrotestosterone in the diagnostics of patients with androgenetic alopecia

Introduction

Androgenetic alopecia (AGA) is the most common form of hair loss. Clinically observed hair loss is due to the continuous miniaturization of affected hair follicles. Genetic factors and androgenic factors especially dihydrotestosterone (DHT), which is a testosterone tissue metabolite, play major roles in the pathogenesis of AGA. However, expert opinions about the usefulness of DHT in the diagnosis of this type of alopecia are divided.

Aim

To evaluate the usefulness of DHT level in patients with androgenetic alopecia compared with the control group.

Material and methods

The study comprised 49 subjects: 19 women and 9 men with androgenetic alopecia. The control group consisted of 17 healthy women and 4 men without hair loss.

Results

Increased serum concentrations of DHT were observed in patients with androgenetic alopecia (17 women, 5 men), but also in the control group. The differences in mean values of DHT were not significant according to the types of alopecia and the control group. Increased serum concentrations of DHT were not correlated with the advance of alopecia.

Conclusions

Dihydrotestosterone is the most influential androgen and seems to play a very important role in the pathogenesis of androgenetic alopecia. Based on the results of our study and others, the most important factors would appear to be the genetically-determined sensitivity of the follicles to DHT and their different reactions to androgen concentration.

Potential targets in the discovery of new hair growth promoters for androgenic alopecia

INTRODUCTION

Androgenic alopecia (AGA) is the major type of scalp hair loss affecting 60 - 70% of the population worldwide. It is caused by two potent androgens, namely testosterone (T) and 5α-dihydrotestosterone (5α-DHT). Till date, only two FDA-approved synthetic drugs, minoxidil and finasteride, are used to cure AGA with only 35 and 48% success, respectively; therefore, a search for new drug based on the mechanism of androgens action is still needed.

AREAS COVERED

Relevant literature was reviewed to identify current therapeutic targets and treatments for AGA. The potential targets are classified into three categories: i) 5α-reductase; ii) androgen receptor and iii) growth-factor-producing genes related to hair growth.

EXPERT OPINION

Relevant assay systems using the right targets are required in order to obtain specific and effective drugs for AGA treatment. It is unlikely that single targeted agents will be sufficient for treating AGA, and therefore, it would be a challenge to obtain compounds with multiple activities.

Avicequinone C isolated from Avicennia marina exhibits 5α-reductase-type 1 inhibitory activity using an androgenic alopecia relevant cell-based assay system

Avicennia marina (AM) exhibits various biological activities and has been traditionally used in Egypt to cure skin diseases. In this study, the methanolic heartwood extract of AM was evaluated for inhibitory activity against 5α-reductase (5α-R) [E.C.1.3.99.5], the enzyme responsible for the over-production of 5α-dihydrotestosterone (5α-DHT) causing androgenic alopecia (AGA). An AGA-relevant cell-based assay was developed using human hair dermal papilla cells (HHDPCs), the main regulator of hair growth and the only cells within the hair follicle that are the direct site of 5α-DHT action, combined with a non-radioactive thin layer chromatography (TLC) detection technique. The results revealed that AM is a potent 5α-R type 1 (5α-R1) inhibitor, reducing the 5α-DHT production by 52% at the final concentration of 10 µg/mL. Activity-guided fractionation has led to the identification of avicequinone C, a furanonaphthaquinone, as a 5α-R1 inhibitor with an IC50 of 9.94 ± 0.33 µg/mL or 38.8 ± 1.29 µM. This paper is the first to report anti-androgenic activity through 5α-R1 inhibition of AM and avicequinone C.

Efficacy of Finasteride for Treating Patients with Androgenetic Alopecia who are Pileous in other Areas: A Pilot Study in Japan

Background:

Androgenetic alopecia (AGA) involves androgen-dependent hair loss and finasteride is an established treatment for the disease. However, reports of the influence of finasteride on hair growth in other areas of the body are lacking.

Aims:

To investigate the effects of finasteride on hair, including the head and other areas of the body.

Materials and Methods:

Based on whether AGA patients felt they were pileous in areas other than the head, they were divided into Group A (pileous) or Group B (not pileous). Finasteride (1 mg/day) was prescribed for both groups for at least 6 months, after which patients were asked to estimate the medicine's effects and any changes of their hair growth.

Results and Conclusions:

A total of 18 out of 37 patients were placed in Group A and 19 of them were in Group B, suggesting that about half of AGA patients in Japan are pileous in other parts of the body. Oral finasteride was effective (excellent or good) in 22 out of 37 (59.5%) patients overall, in 16 out of 18 (88.9%) patients in Group A, and in 6 out of 19 (31.6%) patients in Group B. None of the patients reported that oral finasteride had any effect on their hair growth other than on their head. Finasteride is more effective for treating AGA patients who are pileous in other areas of the body.

The efficacy and safety of 5α-reductase inhibitors in androgenetic alopecia: a network meta-analysis and benefit-risk assessment of finasteride and dutasteride

INTRODUCTION

In the light of post-marketing reports of persistent sexual dysfunction with the use of finasteride, analysis of the extent of risk associated with 5α-reductase inhibitor treatment for androgenetic alopecia (AGA) is warranted. This study sought to evaluate the efficacy of 5α-reductase inhibitors using the outcomes hair count, global photographic assessment and patient self-assessment and evaluate the benefits of treatment versus the risk of global sexual dysfunction.

METHODS

A systematic review identified all relevant randomized controlled trials of finasteride 1 mg, 5 mg and dutasteride 0.5 mg. The efficacy outcome hair count was analyzed using pair-wise meta-analysis, while the efficacy outcomes global photographic assessment and patient self-assessment as well as the safety outcome global sexual dysfunction were analyzed through network meta-analyses. A benefit-risk assessment was also performed.

RESULTS

The active interventions were not significantly different than each other in efficacy and were not significantly different from placebo in eliciting sexual dysfunction. Benefit-risk analysis resulted in an arbitrary ranking due to the lack of statistically significant difference between active treatments.

DISCUSSION

Analysis results reiterate the efficacy and safety of 5α-reductase inhibitors for the treatment of AGA and may support the approval of dutasteride 0.5 mg as an additional treatment option, following further study.

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.

Sex steroid synthesis in human skin in situ: the roles of aromatase and steroidogenic acute regulatory protein in the homeostasis of human skin

Sex steroids have been known to play important roles in the homeostasis of human skin, but little is known about their biosyntheses in that tissue. In this study, we characterized the correlation between the concentrations of sex steroids and the expression levels of the factors involved in their synthesis or metabolism in human skin. The expression levels of aromatase (ARO) and steroidogenic acute regulatory protein (StAR) were positively correlated with estrogens and testosterone concentrations, respectively. We demonstrated that estrogen synthesis was markedly decreased by ARO inhibitor and that skins with higher ARO expression had thicker elastic fibers than those with lower ARO expression. While pregnenolone and testosterone concentrations were increased by cholesterol administration to epidermal keratinocytes. Scalp skin with higher StAR expression was cleared to have significantly fewer hair follicles than that with lower expression. Our results suggest that the status of ARO and StAR contribute to estrogen synthesis in situ, especially for the regulation of elastic fiber formation, and to testosterone synthesis, which may be associated with hair growth, respectively.

The basic science of hair biology: what are the causal mechanisms for the disordered hair follicle?

A hair disorder can be difficult to define, but patients are typically motivated to seek treatment when their hair growth patterns are significantly different from their cultural group or when growth patterns change significantly. The causes of hair disorders are many and varied, but fundamentally the disorder is a consequence of aberrant alterations of normal hair biology. The potential trigger factors for hair disorders can be attributed to inflammation, genetics, the environment, or hormones, of which the relative contributions vary for different diagnoses, between individuals, and over time. This article discusses the causal mechanisms for the disordered hair follicle.

The 5 alpha-reductase isozyme family: a review of basic biology and their role in human diseases

Despite the discovery of 5 alpha-reduction as an enzymatic step in steroid metabolism in 1951, and the discovery that dihydrotestosterone is more potent than testosterone in 1968, the significance of 5 alpha-reduced steroids in human diseases was not appreciated until the discovery of 5 alpha-reductase type 2 deficiency in 1974. Affected males are born with ambiguous external genitalia, despite normal internal genitalia. The prostate is hypoplastic, nonpalpable on rectal examination and approximately 1/10th the size of age-matched normal glands. Benign prostate hyperplasia or prostate cancer does not develop in these patients. At puberty, the external genitalia virilize partially, however, secondary sexual hair remains sparse and male pattern baldness and acne develop rarely. Several compounds have been developed to inhibit the 5 alpha-reductase isozymes and they play an important role in the prevention and treatment of many common diseases. This review describes the basic biochemical properties, functions, tissue distribution, chromosomal location, and clinical significance of the 5 alpha-reductase isozyme family.

Caffeine improves barrier function in male skin

The influence of androgens, especially testosterone and its effector dihydrotestosterone, results in a constitutive disadvantage for male skin, e.g. reduced viability of hair at the scalp and reduced epidermal permeability barrier repair capacity. Dihydrotestosterone can act, among others, as an adenyl cyclase inhibitor. Caffeine on the other hand is an inexpensive and (in regular doses) harmless substance used in various cosmetic products, which can act as a phosphodiesterase inhibitor. To prove the hypothesis that caffeine as a phosphodiesterase inhibitor is able to override testosterone-induced effects on barrier function, we performed a double-blind placebo controlled study with healthy volunteers. In this study, 0.5% caffeine in a hydroxyethylcellulose gel preparation (HEC) was applied on one forearm, HEC without caffeine on the other forearm of male and female volunteers for 7 days and transepidermal water loss (TEWL) was measured before and at the end of the treatment period. Basal TEWL did not differ significantly between male and female subjects but the application of caffeine significantly reduced TEWL in male skin compared with female skin. We conclude that caffeine is beneficial for barrier function in male skin.

Androgens and hair loss

PURPOSE OF REVIEW

Androgenetic alopecia (AGA) or male pattern hair loss is a very common condition that has a significant psychosocial impact for patients. Many advances in the pathogenesis and treatment of AGA have been discovered recently. We discuss the pathogenesis and treatment of AGA.

RECENT FINDINGS

Wide genome analysis showed an association of AGA and chromosome 20pll in addition to androgen-receptor gene. Also, a locus on chromosome 3q26 was found to have a linkage with AGA. Dutasteride has been shown to be more effective than finasteride in the treatment of AGA but is not yet a recommended therapy. In an in-vitro study, a new topical liposomal finasteride formulation showed more than five-fold higher deposition of drug in skin than the corresponding plain drug solution.

SUMMARY

These recent developments in the field of AGA hold some promise and may play a role in the future management.

Male pattern baldness: current treatments, future prospects

Male pattern baldness affects up to half of the male Caucasian population by middle age, and almost all Caucasian men by old age. Especially in younger men, this heritable form of hair loss can have significant psycho-social consequences. Although approved pharmacological agents exist to manage the condition, none of the currently available options are highly efficacious. New treatments under development, and acceleration in our understanding of the underlying molecular genetic aetiology of this condition provide increased hope for future targeted treatment strategies.

The importance of dual 5alpha-reductase inhibition in the treatment of male pattern hair loss: results of a randomized placebo-controlled study of dutasteride versus finasteride

BACKGROUND

Male pattern hair loss (MPHL) is a potentially reversible condition in which dihydrotestosterone is an important etiologic factor.

OBJECTIVE

Our aim was to evaluate the efficacy of the type 1 and 2 5alpha-reductase inhibitor dutasteride in men with MPHL.

METHODS

Four hundred sixteen men, 21 to 45 years old, were randomized to receive dutasteride 0.05, 0.1, 0.5 or 2.5 mg, finasteride 5 mg, or placebo daily for 24 weeks.

RESULTS

Dutasteride increased target area hair count versus placebo in a dose-dependent fashion and dutasteride 2.5 mg was superior to finasteride at 12 and 24 weeks. Expert panel photographic review and investigator assessment of hair growth confirmed these results. Scalp and serum dihydrotestosterone levels decreased, and testosterone levels increased, in a dose-dependent fashion with dutasteride.

LIMITATIONS

The study was limited to 24 weeks.

CONCLUSION

Dutasteride increases scalp hair growth in men with MPHL. Type 1 and type 2 5alpha-reductase may be important in the pathogenesis and treatment of MPHL.

Content of 5-alpha-reductase (type 1 and type 2) mRNA in dermal papillae from the lower abdominal region in women with hirsutism

BACKGROUND

Androgens influence the growth of terminal hair. The dermal papilla contains androgen receptors and the enzymes 5-alpha-reductase types 1 and 2. Both of these enzymes convert testosterone to the more active androgen, 5-alpha-dihydrotestosterone. The male distribution pattern of terminal hair in females is termed hirsutism. It is most common among women with hyperandrogenism; however, it may also affect patients with normal androgen levels (idiopathic hirsutism).

OBJECTIVES

The aim of this study was to assess the expression of 5-alpha-reductase types 1 and 2 mRNA in dermal papillae from the lower abdominal skin in women with hirsutism.

METHODS

The study included 42 subjects, 24 with a diagnosis of polycystic ovary syndrome (PCOS) and 18 with idiopathic hirsutism (IH). In all patients, free serum testosterone was measured.

RESULTS

The mean +/- SD concentration of free serum testosterone was 7.2 +/-5.3 pmol/L in the total group of patients, 10.8 +/- 4.0 pmol/L in patients with PCOS, and 2.5 +/- 1.7 pmol/L in patients with IH. Quantitative analysis was then performed for the mRNA of 5-alpha-reductase types 1 and 2, both of which were found within the dermal papillae from the lower abdominal skin region. The number of mRNA copies/microg of total RNA for 5-alpha-reductase type 1 was statistically significantly higher than that for type 2 in both groups of examined patients. We also demonstrated a positive correlation between the number of mRNA copies/microg of total RNA for 5-alpha-reductase types 1 and 2 and the concentration of free serum testosterone in women with PCOS and IH. Considering all patients together, we found a positive correlation between the number of mRNA copies/microg of total RNA for 5-alpha-reductase type 2 and the concentration of free serum testosterone. There was also a tendency towards a positive correlation between the number of mRNA copies/microg of total RNA for 5-alpha-reductase type 1 and the concentration of free serum testosterone.

CONCLUSION

The results of our study suggest that testosterone increases expression of 5-alpha-reductase types 1 and 2 in dermal papillae from the lower abdominal region in patients with hirsutism.

Evaluation of androgens in the scalp hair and plasma of patients with male-pattern baldness before and after finasteride administration

BACKGROUND

Finasteride, a competitive inhibitor of the enzyme 5alpha-reductase II, is widely used as a medical treatment for patients with male-pattern baldness (MPB), which is affected by the distribution of androgenic steroids. It is also notable that the androgenic effect in MPB is different for each region of the head.

OBJECTIVES

To study the effect of the drug finasteride, we quantified androgenic steroids in the vertex and occipital scalp hair and in the plasma of patients with MPB.

METHODS

The patients with MPB, aged 23-52 years, were treated with finasteride 1 mg daily for 5 months. The hair and plasma samples were hydrolysed, extracted with n-pentane, and derivatized with MSTFA:NH4I:DTE (1000:4:5, v/w/w). We analysed the concentrations of dihydrotestosterone (DHT) and testosterone (T) in the hair and plasma using gas chromatography-mass spectrometry (GC-MS).

RESULTS

In the hair, the ratio of DHT/T was decreased in the vertex scalp hair after the individual received finasteride (P < 0.005). However, we found no significant difference in the ratio of DHT/T in the occipital scalp hair before and after individuals received finasteride. Like the results in the vertex scalp hair, the ratio of DHT/T in the plasma was remarkably decreased after finasteride administration (P < 0.001).

CONCLUSIONS

This study supports the effect of finasteride in patients with MPB by examining the decreased level of DHT/T in scalp hair and in plasma. Thus, in view of the androgenic effect in the different hair regions, the vertex scalp hair plays a more important role for patients with MPB treated with finasteride than does the occipital hair.

Antiandrogen Therapy for Skin and Hair Disease

Androgen hormones play an important role in common skin and hair conditions including acne vulgaris, hirsutism, and androgenetic alopecia. Blocking this androgen effect may lead to significant improvements in these conditions. Several medications that work through a variety of different mechanisms may be prescribed safely and effectively as antiandrogen therapies in the dermatology arena.

Expression of androgen receptor coactivator ARA70/ELE1 in androgenic alopecia

BACKGROUND

Androgens have been implicated in androgenic alopecia as evidenced by the increased cutaneous expression of androgen receptor (AR), 5alpha-reductase, and decreased aromatase. Abnormalities of the AR-signal transduction pathway probably participate in the development of androgenic alopecia. ARA70/ELE1 is an AR coactivator with two isoforms, one full-length form (ARA70alpha/ELE1alpha), and an internally deleted form (ARA70beta/ELE1beta). We decided to examine the cutaneous expression of both isoforms in male androgenic alopecia.

METHODS

Formalin-fixed, paraffin-embedded tissue sections from seven subjects with androgenic alopecia with matched punch biopsies from non-balding and balding areas were examined by in situ hybridization.

RESULTS

Expression of at least one of the two probes for ARA70/ELE1 was present in all phases of the hair-growth cycle in all epithelial hair structures except for the inner root sheath. The dermal papilla and hair bulb expressed only the short (beta) but not the long (alpha) form of ARA70/ELE1. In situ labeling for ARA70beta/ELE1beta was weaker in the dermal papilla of balding recipient areas than those from donor ones.

CONCLUSIONS

Our data further support that the hair growth is regulated by androgens. The differential expression pattern of ARA70/ELE1 suggests that this key androgen receptor coactivator is involved in androgenic alopecia. Lee P, Zhu C-C, Sadick NS, Diwan AH, Zhang PS, Liu JS, Prieto VG. Expression of androgen receptor coactivator ARA70/ELE1 in androgenic alopecia.

5alpha-reductase in human embryonic kidney cell line HEK293: evidence for type II enzyme expression and activity

Human 5alpha-reductase catalyses the last step in androgen biosynthesis, namely the reduction of testosterone (T) to the more potent androgen dihydrotestosterone (DHT). The enzyme is therefore considered to be an important drug target for androgen related diseases such as benign prostatic hyperplasia and prostate cancer. The present study displays evidence that the human embryonic kidney cell line HEK293 which is frequently used in recombinant target protein expression contains an endogenous 5alpha-reductase type II activity. After an incubation of 24 h 1 x 10(6) HEK293 cells converted 23% of the substrate 4-androstene-3,17-dione (7.5 nM) to the product 5alpha-androstane-3,17-dione. Reverse transcription polymerase chain reaction was carried out to identify the mRNA of the isoform responsible for the 5alpha-reductase activity. Only with type II specific primers a fragment with the predicted size was amplified, while with type I specific primers no band could be observed. An antiserum against human 5alpha-reductase type II was raised by immunizing a rabbit with a hemocyanin-conjugated peptide corresponding to amino acid 29 to 44 of the type II enzyme. Western blot analysis of different fractions of a HEK293 homogenate performed with this antiserum detected a band at 45 kDa in the nuclear and microsomal fraction corresponding to 5alpha-reductase type II protein.

Rooster feathering, androgenic alopecia, and hormone-dependent tumor growth: what is in common?

Different epithelial organs form as a result of epithelial-mesenchymal interactions and share a common theme modulated by variations (Chuong ed. In Molecular Basis of Epithelial Appendage Morphogenesis, 1998). One of the major modulators is the sex hormone pathway that acts on the prototype signaling pathway to alter organ phenotypes. Here, we focus on how the sex hormone pathway may interface with epithelia morphogenesis-related signaling pathways. We first survey these sex hormone-regulated morphogenetic processes in various epithelial organs. Sexual dimorphism of hairs and feathers has implications in sexual selection. Diseases of these pathways result in androgenic alopecia, hirsutism, henny feathering, etc. The growth and development of mammary glands, prostate glands, and external genitalia essential for reproductive function are also dependent on sex hormones. Diseases affecting these organs include congenital anomalies and hormone-dependent breast and prostate cancers. To study the role of sex hormones in new growth in the context of system biology/pathology, an in vivo model in which organ formation starts from stem cells is essential. With recent developments (Yu et al. (2002) The morphogenesis of feathers. Nature 420:308-312), the growth of tail feathers in roosters and hens has become a testable model in which experimental manipulations are possible. We show exemplary data of differences in their growth rate, proliferative cell population, and signaling molecule expression. Working hypotheses are proposed on how the sex hormone pathways may interact with growth pathways. It is now possible to test these hypotheses using the chicken model to learn fundamental mechanisms on how sex hormones affect organogenesis, epithelial organ cycling, and growth-related tumorigenesis.

Selective non-steroidal inhibitors of 5 alpha-reductase type 1

The enzyme 5 alpha-reductase (5 alpha R) catalyses the reduction of testosterone (T) into the more potent androgen dihydrotestosterone (DHT). The abnormal production of DHT is associated to pathologies of the main target organs of this hormone: the prostate and the skin. Benign prostatic hyperplasia (BPH), prostate cancer, acne, androgenetic alopecia in men, and hirsutism in women appear related to the DHT production. Two isozymes of 5 alpha-reductase have been cloned, expressed and characterized (5 alpha R-1 and 5 alpha R-2). They share a poor homology, have different chromosomal localization, enzyme kinetic parameters, and tissue expression patterns. Since 5 alpha R-1 and 5 alpha R-2 are differently distributed in the androgen target organs, a different involvement of the two isozymes in the pathogenesis of prostate and skin disorders can be hypothesized. High interest has been paid to the synthesis of inhibitors of 5 alpha-reductase for the treatment of DHT related pathologies, and the selective inhibition of any single isozyme represents a great challenge for medical and pharmaceutical research in order to have more specific drugs. At present, no 5 alpha R-1 inhibitor is marketed for the treatment of 5 alpha R-1 related pathologies but pharmaceutical research is very active in this field. This paper will review the major classes of 5 alpha R inhibitors focusing in particular on non-steroidal inhibitors and on structural features that enhance the selectivity versus the type 1 isozyme. Biological tests to assess the inhibitory activity towards the two 5 alpha R isozymes will be also discussed.

Androgen Replacement Therapy

The major goal of androgen substitution is to replace testosterone at levels as close to physiological levels as is possible. For some androgen-dependent functions testosterone is a pro-hormone, peripherally converted to 5alpha-dihydrotestosterone (DHT) and 17beta-estradiol (E2), of which the levels preferably should be within normal physiological ranges. Furthermore, androgens should have a good safety profile without adverse effects on the prostate, serum lipids, liver or respiratory function, and they must be convenient to use and patient-friendly, with a relative independence from medical services. Natural testosterone is viewed as the best androgen for substitution in hypogonadal men. The reason behind the selection is that testosterone can be converted to DHT and E2, thus developing the full spectrum of testosterone activities in long-term substitution. The mainstays of testosterone substitution are parenteral testosterone esters (testosterone enantate and testosterone cipionate) administered every 2-3 weeks. A major disadvantage is the strongly fluctuating levels of plasma testosterone, which are not in the physiological range at least 50% of the time. Also, the generated plasma E2 is usually supraphysiological. A major improvement is parenteral testosterone undecanoate producing normal plasma levels of testosterone for 12 weeks, with normal plasma levels of DHT and E2 also. Subcutaneous testosterone implants provide the patient, depending on the dose of implants, with normal plasma testosterone for 3-6 months. However, their use is not widespread. Oral testosterone undecanoate dissolved in castor oil bypasses the liver via its lymphatic absorption. At a dosage of 80 mg twice daily, plasma testosterone levels are largely in the normal range, but plasma DHT tends to be elevated. For two decades transdermal testosterone preparations have been available and have an attractive pharmacokinetic profile. Scrotal testosterone patches generate supraphysiological plasma DHT levels, which is not the case with the nonscrotal testosterone patches. Transdermal testosterone gel produces fewer skin irritations than the patches and offers greater flexibility in dosage. Oromucosal testosterone preparations have recently become available. Testosterone replacement is usually of long duration and so patient compliance is of utmost importance. Therefore, the patient must be involved in the selection of type of testosterone preparation. Administration of testosterone to young individuals has almost no adverse effects. With increasing age the risk of adverse effects on the prostate, the cardiovascular system and erythropoiesis increases. Consequently, short-acting testosterone preparations are better suited for aging androgen-deficient men.

The 5alpha-reductase type 1, but not type 2, gene is expressed in anagen hairs plucked from the vertex area of the scalp of hirsute women and normal individuals

The aim of the present study was to determine the expression of the genes for type 1 (SDR5A1) and type 2 (SDR5A2) 5alpha-reductase isoenzymes in scalp hairs plucked from 33 hirsute patients (20 with polycystic ovary syndrome and 13 with idiopathic hirsutism) and compare it with that of 10 men and 15 normal women. SDR5A1 and SDR5A2 expression was estimated by RT-PCR using the gene of the ubiquitously expressed protein 2-microglobulin as an internal control. The results are expressed as arbitrary units in relation to beta2-microglobulin absorbance (mean SEM). SDR5A2 expression was not detected in any hair samples analyzed in this study. No differences were found in SDR5A1 mRNA levels between men and normal women (0.78+/-0.05 vs 0.74+/-0.06, respectively). SDR5A1 gene expression in the cells of hair plucked from the scalp of normal women (0.85+/-0.04) and of women with polycystic ovary syndrome (0.78+/-0.05) and idiopathic hirsutism (0.80+/-0.06) was also similar. These results indicate that SDR5A1 gene expression in the follicular keratinocytes from the vertex area of the scalp seems not to be related to the differences in hair growth observed between normal men and women and hirsute patients. Further studies are needed to investigate the expression of the 5alpha-reductase genes in other scalp follicular compartments such as dermal papillae, and also in hair follicles from other body sites, in order to elucidate the mechanism of androgen action on the hair growth process and related diseases.

Human skin is a steroidogenic tissue: steroidogenic enzymes and cofactors are expressed in epidermis, normal sebocytes, and an immortalized sebocyte cell line (SEB-1)

Although the human sebaceous gland can synthesize cholesterol from acetate and can further metabolize steroids such as dehydroepiandrosterone into potent androgens, the de novo production of steroids from cholesterol has not been demonstrated in human skin. The goal of this study was to delineate the steroidogenic pathway upstream from dehydroepiandrosterone by documenting the presence of members of the P450 side chain cleavage system (P450scc). This system catalyzes the initial step in steroid hormone synthesis following translocation of cholesterol to the inner mitochondrial membrane. In concert with its cofactors, adrenodoxin and adrenodoxin reductase, and the transcription factor steroidogenic factor 1, P450scc converts cholesterol to pregnenolone. An SV40 immortalized human sebaceous gland cell line (SEB-1) was established in order to facilitate investigation of the P450scc system. The sebaceous phenotype of SEB-1 sebocytes was confirmed using immunohistochemistry, Oil Red O staining, and gene array expression analysis. Presence of P450scc, adrenodoxin reductase, cytochrome P450 17-hydroxylase (P450c17), and steroidogenic factor 1 was documented in human facial skin, human sebocytes, and SEB-1 sebocytes. Using immunohistochemistry, antibodies to the above proteins localized to epidermis, hair follicles, sebaceous ducts, and sebaceous glands in sections of facial skin. Results of immunohistochemistry were confirmed with Western blotting. Biochemical activity of cytochrome P450scc and P450c17 was demonstrated in SEB-1 sebocytes using radioimmunoassay. The relative abundance of mRNA for P450scc, P450c17, and steroidogenic factor 1 in SEB-1 sebocytes and sebaceous glands was compared to mRNA levels in ovarian theca and granulosa cells using real-time quantitative polymerase chain reaction. Gene array expression analysis and quantitative polymerase chain reaction indicated that mRNA for P450scc is more abundant than mRNA for both P450c17 and steroidogenic factor 1 in sebaceous glands and SEB-1 cells. These data demonstrate that the skin is in fact a steroidogenic tissue. The clinical significance of this finding in mediating androgenic skin disorders such as acne, hirsutism, or androgenetic alopecia remains to be established.

New evidence of similarity between human and plant steroid metabolism: 5alpha-reductase activity in Solanum malacoxylon

The physiological role of steroid hormones in humans is well known, and the metabolic pathway and mechanisms of action are almost completely elucidated. The role of plant steroid hormones, brassinosteroids, is less known, but an increasing amount of data on brassinosteroid biosynthesis is showing unexpected similarities between human and plant steroid metabolic pathways. Here we focus our attention on the enzyme 5alpha-reductase (5alphaR) for which a plant ortholog of the mammalian system, DET2, was recently described in Arabidopsis thaliana. We demonstrate that campestenone, the natural substrate of DET2, is reduced to 5alpha-campestanone by both human 5alphaR isozymes but with different affinities. Solanum malacoxylon, which is a calcinogenic plant very active in the biosynthesis of vitamin D-like molecules and sterols, was used to study 5alphaR activity. Leaves and calli were chosen as examples of differentiated and undifferentiated tissues, respectively. Two separate 5alphaR activities were found in calli and leaves of Solanum using campestenone as substrate. The use of progesterone allowed the detection of both activities in calli. Support for the existence of two 5alphaR isozymes in S. malacoxylon was provided by the differential actions of inhibitors of the human 5alphaR in calli and leaves. The evidence for the presence of two isozymes in different plant tissues extends the analogies between plant and mammalian steroid metabolic pathways.

Androgens and alopecia

Androgens have profound effects on scalp and body hair in humans. Scalp hair grows constitutively in the absence of androgens, while body hair growth is dependent on the action of androgens. Androgenetic alopecia, referred to as male pattern hair loss (MPHL) in men and female pattern hair loss (FPHL) in women, is due to the progressive miniaturization of scalp hair. Observations in both eunuchs, who have low levels of testicular androgens, and males with genetic 5alpha-reductase (5alphaR) deficiency, who have low levels of dihydrotestosterone (DHT), implicate DHT as a key androgen in the pathogenesis of MPHL in men. The development of finasteride, a type 2-selective 5alphaR inhibitor, further advanced our understanding of the role of DHT in the pathophysiology of scalp alopecia. Controlled clinical trials with finasteride demonstrated improvements in scalp hair growth in treated men associated with reductions in scalp DHT content, and a trend towards reversal of scalp hair miniaturization was evident by histopathologic evaluation of scalp biopsies. In contrast to its beneficial effects in men, finasteride did not improve hair growth in postmenopausal women with FPHL. Histopathological evaluation of scalp biopsies confirmed that finasteride treatment produced no benefit on scalp hair in these women. These findings suggest that MPHL and FPHL are distinct clinical entities, with disparate pathophysiologies. Studies that elucidate the molecular mechanisms by which androgens regulate hair growth would provide greater understanding of these differences.

Cutaneous androgen metabolism: basic research and clinical perspectives

The skin, especially the pilosebaceous unit composed of sebaceous glands and hair follicles, can synthesize androgens de novo from cholesterol or by locally converting circulating weaker androgens to more potent ones. As in other classical steroidogenic organs, the same six major enzyme systems are involved in cutaneous androgen metabolism, namely steroid sulfatase, 3beta-hydroxy-steroid dehydrogenase, 17beta-hydroxysteroid dehydrogenase, steroid 5alpha-reductase, 3alpha-hydroxysteroid dehydrogenase, and aromatase. Steroid sulfatase, together with P450 side chain cleavage enzyme and P450 17-hydroxylase, was found to reside in the cytoplasm of sebocytes and keratinocytes. Strong steroid sulfatase immunoreactivity was observed in the lesional skin but not in unaffected skin of acne patients. 3beta-hydroxysteroid dehydrogenase has been mainly immunolocalized to sebaceous glands, with the type 1 being the key cutaneous isoenzyme. The type 2 17beta-hydroxysteroid dehydrogenase isoenzyme predominates in sebaceous glands and exhibits greater reductive activity in glands from facial areas compared with acne nonprone areas. In hair follicles, 17beta-hydroxysteroid dehydrogenase was identified mainly in outer root sheath cells. The type 1 5alpha-reductase mainly occurs in the sebaceous glands, whereby the type II isoenzyme seems to be localized in the hair follicles. 3alpha-hydroxysteroid dehydrogenase converts dihydrotestosterone to 3alpha-androstanediol, and the use of 3alpha-androstanediol glucuronide serum level to reflect the hyperandrogenic state in hirsute women may be a reliable parameter, especially for idiopathic hirsutism. In acne patients it is still controversial if 3alpha-androstanediol glucuronide or androsterone glucuronide could serve as suitable serum markers for measuring androgenicity. Aromatase, localized to sebaceous glands and to both outer as well as inner root sheath cells of anagen terminal hair follicles, may play a "detoxifying" role by removing excess androgens. Pharmacologic development of more potent specific isoenzyme antagonists may lead to better clinical treatment or even prevention of androgen-dependent dermatoses.