Metabolism of dihydrotestosterone to 5 alpha-androstane-3 alpha, 17 beta-diol glucuronide is greater in the peripheral compartment than in the splanchnic compartment

Androgen receptor agonists increase lean mass, improve cardiopulmonary functions and extend survival in preclinical models of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a neuromuscular disease that predominantly affects boys as a result of mutation(s) in the dystrophin gene. DMD is characterized by musculoskeletal and cardiopulmonary complications, resulting in shorter life-span. Boys afflicted by DMD typically exhibit symptoms within 3-5 years of age and declining physical functions before attaining puberty. We hypothesized that rapidly deteriorating health of pre-pubertal boys with DMD could be due to diminished anabolic actions of androgens in muscle, and that intervention with an androgen receptor (AR) agonist will reverse musculoskeletal complications and extend survival. While castration of dystrophin and utrophin double mutant (mdx-dm) mice to mimic pre-pubertal nadir androgen condition resulted in premature death, maintenance of androgen levels extended the survival. Non-steroidal selective-AR modulator, GTx-026, which selectively builds muscle and bone was tested in X-linked muscular dystrophy mice (mdx). GTx-026 significantly increased body weight, lean mass and grip strength by 60-80% over vehicle-treated mdx mice. While vehicle-treated castrated mdx mice exhibited cardiopulmonary impairment and fibrosis of heart and lungs, GTx-026 returned cardiopulmonary function and intensity of fibrosis to healthy control levels. GTx-026 elicits its musculoskeletal effects through pathways that are distinct from dystrophin-regulated pathways, making AR agonists ideal candidates for combination approaches. While castration of mdx-dm mice resulted in weaker muscle and shorter survival, GTx-026 treatment increased the muscle mass, function and survival, indicating that androgens are important for extended survival. These preclinical results support the importance of androgens and the need for intervention with AR agonists to treat DMD-affected boys.

Dihydrotestosterone: Biochemistry, Physiology, and Clinical Implications of Elevated Blood Levels

Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicates that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/testosterone (T) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. Although the primary focus of this review is about DHT in men, we also provide a brief overview of DHT in women. The available published data are limited by the lack of large, well-controlled studies of long duration that are sufficiently powered to expose subtle safety signals. Nonetheless, the preponderance of available clinical data indicates that modest elevations in circulating levels of DHT in response to androgen therapy should not be of concern in clinical practice. Elevated DHT has not been associated with increased risk of prostate disease (e.g., cancer or benign hyperplasia) nor does it appear to have any systemic effects on cardiovascular disease safety parameters (including increased risk of polycythemia) beyond those commonly observed with available T preparations. Well-controlled, long-term studies of transdermal DHT preparations have failed to identify safety signals unique to markedly elevated circulating DHT concentrations or signals materially different from T.

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.

Relationship of sex steroid hormones with body size and with body composition measured by dual-energy X-ray absorptiometry in US men

PURPOSE

To evaluate the association of body size-captured via whole-body dual-energy X-ray absorptiometry (DXA) and physical measurement-with serum sex steroid hormones and sex hormone binding globulin (SHBG), we utilized cross-sectional data and serum samples from the National Health and Nutrition Examination Survey (NHANES; 1999-2004).

METHODS

Testosterone, androstanediol glucuronide (3-alpha-diol-G), estradiol, and SHBG were measured via immunoassay in serum samples from a total of 898 adult men (ages 20-90) participating in the morning examination. As part of the NHANES data collection, DXA scans and measurements of weight, height, and waist circumference were performed by trained staff. Linear regression was used to estimate associations between body size and hormone levels adjusted for potential confounders and NHANES sampling procedures.

RESULTS

Total bone area (cm(2)) was inversely associated with total testosterone (ng/mL) [beta = -0.12; p value < 0.01], while bone mineral density (g/cm(2)) was inversely associated with SHBG (nmol/L) [beta = -17.16; p value = 0.01]. Increased percent body fat was associated with lower concentrations of total testosterone [beta = -0.16; p value < 0.01] and SHBG [beta = -1.11; p value < 0.01] and higher concentrations of free estradiol (fg/mL) [beta = 12.52; p value < 0.01].

CONCLUSIONS

Clinical measures of body fat (measured via DXA scan) and anthropometric measures of body fat (BMI and waist circumference) provided similar inferences regarding the association between increased body fat and hormone levels in men. Increased body fat was associated with lower circulating levels of testosterone (total and free) and SHBG and higher circulating levels of free estradiol in men, while decreased bone mineral density was associated with higher circulating levels of SHBG.

3alpha-Hydroxysteroid dehydrogenase type III deficiency: a novel mechanism for hirsutism

CONTEXT

Dihydrotestosterone (DHT), the primary active androgen in peripheral target tissues, is metabolized by 3alpha-hydroxysteroid dehydrogenase type III (3alpha-HSD), encoded by the AKR1C2 gene, forming 5alpha-androstane-3alpha,17beta-diol (3alpha-diol). 3alpha-HSD may play a role in the pathogenesis of hirsutism.

OBJECTIVES

Our objective was to evaluate the role of 3alpha-HSD in hirsutism by comparing 1) tissue levels of active androgens, 2) relative gene expression of AKR1C2, and 3) activity of 3alpha-HSD in genital skin from normal and hirsute women.

DESIGN

Genital skin was obtained from normal and hirsute women. After homogenization, testosterone (T) and DHT levels were quantified by conventional RIA. From isolated RNA, relative expression of AKR1C2 was determined by real-time PCR. In addition, minced genital skin was incubated with [(3)H]DHT, and the product, [(3)H]3alpha-diol, was quantified by radio-HPLC.

SETTING

The study took place at an inner-city hospital.

PATIENTS

PATIENTS included women undergoing posterior colporrhaphy.

MAIN OUTCOME MEASURES

We assessed 1) tissue levels of T, DHT, and 3alpha-diol; 2) relative expression of AKR1C2; and 3) conversion ratio of [(3)H]3alpha-diol to [(3)H]DHT.

RESULTS

In genital skin, tissue DHT and T concentrations in hirsute women were 1.90-fold and 1.84-fold higher than in normal women (P =0 .002 and 0.03), and relative expression of AKR1C2 mRNA was reduced approximately 7-fold (P = 0.04). Genital skin from hirsute women showed less metabolism of [(3)H]DHT to [(3)H]3alpha-diol (conversion ratio, 0.24 +/- 0.19 vs. 0.85 +/- 0.55, P = 0.01).

CONCLUSIONS

In genital skin of hirsute women, reduced AKR1C2 gene expression and 3alpha-HSD activity results in decreased DHT metabolism and elevated tissue levels of DHT. Diminished DHT metabolism may play an important role in the pathogenesis of hirsutism.

Serum levels of 3α-androstanediol glucuronide in young women with polycystic ovary syndrome, idiopathic hirsutism and in normal subjects

OBJECTIVE

The study objective was to assess the role of 3alpha-androstanediol glucuronide (3alpha-diolG) as the marker of peripheral androgen action in the young women with hirsutism diagnosed as polycystic ovary syndrome (PCOS), in patients with idiopathic hirsutism (IH) and in normal non-hirsute women.

STUDY DESIGN

Fifty-nine young women with mean age 21.90+/-3.52 years suffered from hirsutism were included in the study. Among these 59 hirsute women 31 women with mean age 21.60+/-3.56 years were diagnosed as PCOS and 28 women with mean age 22.20+/-3.59 years were classified as idiopathic hirsutism patients. Twenty-seven normal women, age-matched (mean age 22.60+/-2.90 years), without signs of hirsutism and with normal menstrual cycle served as control for this study. Serum was collected from women with hirsutism (due to PCOS or idiopathic hirsutism) and from non-hirsute women. Serum levels of 3alpha-androstanediol glucuronide (3alpha-diolG), main androgens such as: testosterone, free testosterone, dehydroepiandrosterone (DHEAS) and also others hormones such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2) and sex hormone-binding globuline (SHBG) were measured using radioimmunoassay (RIA) method in the study and control group. Hirutism was assessed using modified Ferriman-Gallwey method. Serum 3alpha-diolG levels in PCOS women were significantly higher than in controls.

RESULTS

There were no significant differences between serum 3alpha-diolG levels in PCOS group and IH group. Similarly, there were significant differences between serum 3alpha-diolG levels in IH group and control subjects.

CONCLUSION

We conclude that 3alpha-diolG is not useful as the marker for peripheral androgen metabolism and for differentiation between idiopathic hirsutism and PCO-related hirsutism.

Proposed mechanism for sperm chromatin condensation/decondensation in the male rat

Condensation of sperm chromatin occurs after spermatozoa have left the caput epididymis and are in transit to the cauda epididymis, during which time large numbers of disulfide bonds are formed. The formation of these disulfide bonds requires the repeated oxidation of the cofactor, NAD(P)H. To date, the means by which this oxidation is achieved has yet to be elucidated. Spermatozoa lose the bulk of their cytoplasm prior to leaving the testis; and, as a result, any shuttle systems for removing and transferring reducing equivalents into the mitochondria are unlikely to be operational. In an apparent preparation for the loss of cytoplasm, however, the following events occur during spermatogenesis. First, androgen-binding protein (ABP) is produced by the Sertoli cells of the testis; second, high affinity binding sites for ABP are inserted into the membrane surrounding the nucleus; and third, a nuclear location is acquired for the enzyme, 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD). We propose that after the loss of cytoplasm, the nuclear region of spermatozoa is directly accessible to constituents contained in the lumen of the caput epididymis. As a consequence, luminal ABP attaches itself to the nuclear membrane via its binding sites, and is internalized. After internalization, ABP exerts its principle function, which is to bind to luminal 5alpha-dihydrotestosterone (5alpha-DHT), thereby ensuring its availability to the enzyme, 3alpha-HSD. In the conversion of 5alpha-DHT to 3alpha-androstanediol (3alpha-Diol), NAD(P)H is oxidized. Spermatozoa that reach the cauda epididymis have fully condensed chromatin. In addition, the nuclear region retains appreciable amounts of 5alpha-DHT and 3alpha-Diol, both bound to ABP. During fertilization, the bound 3alpha-Diol is converted back to 5alpha-DHT, reducing equivalents are transferred to NAD(P)+, and disulfide bonds are broken.IVF clinics report that spermatozoa with incompletely condensed chromatin have a low percentage of fertilization. If our proposed mechanism for chromatin condensation/decondensation is borne out by further research, IVF clinics might consider preincubating spermatozoa with 5alpha-DHT in order to increase the efficiency of fertilization.

Acne and hirsutism in polycystic ovary syndrome: clinical, endocrine-metabolic and ultrasonographic differences

The aim of this study was to investigate whether the absence or presence of acne or hirsutism in 248 women with polycystic ovary syndrome was associated with different clinical, endocrine, metabolic and ultrasonographic factors. Patients were divided into three groups: 96 (38.7%) without any androgenic symptoms; 94 (37.9%) with only hirsutism; and 58 (23.4%) with only acne. The cycle alterations (oligomenorrhea or amenorrhea) and the echographic ovarian morphology (polycystic or multifollicular ovaries) showed no significant differences between the three groups. Hirsutism was associated with a greater incidence of obesity and insulin resistance, with an increase of 17-hydroxyprogesterone, ovarian and adrenal androgens, 3alpha-androstanediol glucuronide, insulin, insulin-like growth factor-I and low luteinizing hormone, sex hormone binding globulins and insulin-like growth factor binding protein-1 levels. Acne was associated only with the lowest 3alpha-androstanediol glucuronide levels. Therefore, two different pathogenetic mechanisms may play a role in the onset of acne and hirsutism.

Androgens in postmenopausal women: production, possible role, and replacement options

The physiology of normal androgen production in women has not been well understood. Aging, per se, accounts for much of the reduction in both ovarian and adrenal androgen production; and natural menopause does not result in an abrupt decline in testosterone production. Therefore, the definition of an androgen deficiency state in women, in the absence of adrenal suppression and/or bilateral oophorectomy, has been difficult. Nevertheless there are well-documented beneficial effects of androgen on many organ systems, including bone and the brain. This review focuses on the physiology of androgens in postmenopausal women and includes a discussion of the definition of an androgen deficiency state, the anticipated effects of androgen on several parameters of health, and possible ways in which androgens may be administered to women.

Effect of percutaneous androgen replacement therapy on body composition and body weight in postmenopausal women

OBJECTIVES

This study was carried out to assess the effect of topical androgen replacement therapy on body weight, body composition and fat distribution in postmenopausal women.

METHODS

39 healthy postmenopausal women (51.4 +/- 2.24 years), with increasing body weight, were prospectively studied for 6 months. Body composition (fat mass, kg, %) was measured by means of dual-energy X-ray absorptiometry (DXA). Hormonal and lipid parameters were also measured. Subjects were divided into two groups. An androgen gel (group A) or placebo gel (group P) was topically administered to the abdominal and gluteo-femoral regions. DXA was performed before commencement of topical treatment and after 6 months.

RESULTS

A highly significant total body weight reduction was found in group A (68.0 +/- 13.1 to 65.4 +/- 11.8 kg). Abdominal fat (37.3 +/- 11.2 to 35.1 +/- 9.7%), gluteo-femoral fat (46.3 +/- 6.6 to 45.4 +/- 7.7%), total body fat (38.2 +/- 7.9 to 36.1 +/- 8.6%) and BMI (24.8 +/- 4.3 to 23.7 +/- 3.8) were also found to have decreased significantly in this group. No significant reduction in body weight (kg) and body fat (%) could be measured in the placebo group. No influence on lipid parameters was found although total testosterone increased significantly in group A (0.29 +/- 0.24 to 0.72 +/- 0.17 ng/ml).

CONCLUSIONS

Topically applied androgen is capable of reducing abdominal fat accumulations as well as total body weight in postmenopausal women with unexplained weight gain. In contrast to systemic androgen application, topical administration has no effect on the lipid profile. Gluteal fat, however, is less effectively influenced by androgens.