Preserved male fertility despite decreased androgen sensitivity caused by a mutation in the ligand-binding domain of the androgen receptor gene

Mutations in the androgen receptor gene are considered as incompatible with preservation of fertility and have been suggested as a cause of male infertility. Two adult brothers, referred because of gynecomastia and hormonal levels in serum indicating androgen insensitivity (high sex hormone-binding globulin, and LH levels, despite extremely high testosterone concentration), turned out to be relatives to a third young man, referred independently of the two others and exhibiting identical clinical and hormonal stigmata. In all three men, we found a C-->A substitution at position 2470 (exon 7) in the androgen receptor gene, leading to a Gln824Lys mutation in the ligand-binding domain of the receptor. Exploring the family history revealed that their grandfathers, on their mothers' side, were brothers; and the Gln824Lys mutation was also found in the one of them who was still alive. Binding studies with the mutant receptor in transfected COS-7 cells, with mibolerone as ligand, exhibited equal Kd (0.7 vs. 1.0 nmol/ L), IC50 (0.8 vs. 1.1 nmol/L), and maximum binding (7.1 vs. 8.9 fmol/ 10(6) cells), as compared with the wild-type (WT) receptor. In a chloramphenicol acetyl transferase trans-activation assay, the activity of the mutant receptor was identical to that of the WT, when the synthetic androgen R1881 was'used as a ligand; but with dihydrotestosterone, in concentrations up to 10 nmol/L, the activity of Gln824Lys mutated receptor was 10-62% of the WT variant. Thus, Gln824Lys mutation was found, both in vivo and in vitro, to cause slight impairment of receptor function but was compatible with preservation of male fertility. The patients inherited the mutation from their grandfathers through their mothers, and one of the young men possessing the mutation has fathered a daughter.     

Correlation of clinical, endocrine and molecular abnormalities with in vivo responses to high-dose testosterone in patients with partial androgen insensitivity syndrome

OBJECTIVE To investigate the responses of two patients previously diagnosed as Reifenstein's syndrome to graded high-dose testosterone in terms of hormone levels, nitrogen balance and sebum secretion and to attempt to correlate these parameters with the properties of their androgen receptors and mutations in the androgen receptor gene. DESIGN Nitrogen balance was determined by comparing controlled nitrogen intake to the amount excreted. Sebum excretion was measured on the forehead. Patients were studied during control periods (no treatment) and during administration of testosterone propionate. Blood samples were used as a source of genomic DNA and to measure peripheral hormone levels; androgen receptor binding was determined using genital skin fibroblasts. PATIENTS Two patients of XY karyotype, with ambiguous external genitalia and problems of testicular descent who had required mastectomy as teenagers. Normal male controls of proven fertility. MEASUREMENTS Nitrogen balance, sebum excretion rate and peripheral hormone levels (testosterone, dihydrotestosterone, LH and FSH) were studied before and after testosterone therapy (1 or 5 mg/kg/day). Genomic DNA was extracted from peripheral blood leucocytes and regions of the androgen receptor gene amplified by polymerase chain reaction using pairs of specific primers. Mobility of amplified DNA from patients was analysed on denaturing gradient acrylamide gels and fragments differing in mobility from those of normal controls were sequenced. Fibroblasts were cultured from scrotal skin biopsies and androgen receptor binding parameters, subcellular localization and up-regulation were determined. RESULTS Testosterone therapy resulted in raised plasma testosterone, dihydrotestosterone and oestradiol in both patients. In patient 1 (lesser genital abnormality), LH was suppressed by 5 mg/kg/day testosterone to the upper limit of the normal range but FSH remained low normal. Both LH and FSH were suppressed by testosterone treatment in patient 2 (greater genital abnormality). Nitrogen retention was increased in both patients (4.2 and 3.0 g/24 h respectively); sebum excretion rate increased to normal in patient 1 but showed no change in patient 2. Mutations in the androgen receptor gene were identified in both patients. In patient 1 a single nucleotide change from adenosine to guanosine resulted in the substitution of glycine for glutamic acid at position 772 within the hormone binding domain of the receptor. In patient 2 a single nucleotide mutation from guanosine to adenosine resulted in the substitution of lysine for arginine at position 608 (exon 3) situated in the second zinc finger of the DNA binding domain. Both patients had a normal number of androgen binding sites in genital skin fibroblasts but those in patient 1 showed reduced binding affinity and rapid dissociation of receptor/ligand complexes while those in patient 2 showed defective nuclear localization. CONCLUSION In patients with partial androgen insensitivity syndrome the type of androgen receptor mutation and responses to short-term androgen treatment can be correlated with the individual’s potential to virilize. If there is a mutation in the androgen receptor DNA binding domain the patient may show little ability to virilize either spontaneously at puberty or after androgen treatment. Sebum excretion appears to be more discriminating than nitrogen balance or gonadotrophin supression as an index of tissue response to androgens.     

Visceral and subcutaneous adipose tissue assessed by magnetic resonance imaging in relation to circulating androgens, sex hormone-binding globulin, and luteinizing hormone in young men

CONTEXT: No large studies of young men have examined circulating sex hormones in relation to visceral and sc adipose tissues. OBJECTIVE: The aim of this study was to investigate the role of visceral adipose tissue and sc adipose tissue on circulating sex hormones and the impact of obesity on sex hormone reference intervals. DESIGN, SETTING, AND PARTICIPANTS: Population-based study of 783 Danish 20- to 29-yr-old men was performed using dual-energy x-ray absorptiometry in all men and magnetic resonance imaging in 406 men. MAIN OUTCOME MEASURES: Total, bioavailable, and free testosterone, dihydrotestosterone (DHT), total and bioavailable estradiol, SHBG, and LH were measured. RESULTS: In multiple regressions, visceral adipose tissue was an independent, inverse correlate of bioavailable and free testosterone. Subcutaneous adipose tissue correlated negatively with SHBG and positively with bioavailable estradiol adjusted for total testosterone. Both visceral adipose tissue and sc adipose tissue correlated inversely with total testosterone and DHT. Adjusting for SHBG, only visceral adipose tissue remained significantly correlated. Low total testosterone in viscerally obese men was not accompanied by increased LH. The androgen reference intervals were significantly displaced toward lower limits in obese vs. nonobese men (total testosterone: 8.5-29.3 vs. 12.5-37.6 nmol/liter; bioavailable testosterone: 6.1-16.9 vs. 7.6-20.7 nmol/liter; free testosterone: 0.23-0.67 vs. 0.29-0.78 nmol/liter; and DHT: 0.63-2.5 vs. 0.85-3.2 nmol/liter), whereas total estradiol (36.5-166 pmol/liter) and bioavailable estradiol (23.4-120 pmol/liter) reference intervals were not. In obese men, 22.9% had total testosterone less than 12.5 nmol/liter. CONCLUSIONS: Visceral adipose tissues correlate independently with bioavailable and free testosterone in young men. The inverse relationship between total testosterone and sc adipose tissue seems to be accounted for by variations in SHBG. The reference intervals for total testosterone, bioavailable testosterone, free testosterone, and DHT are displaced toward lower limits in obese men.     

The frequency of androgen receptor deficiency in infertile men

To ascertain the frequency of androgen resistance as the cause of male infertility and to determine whether endocrine abnormalities are a universal feature of the disorder, we measured the androgen receptor in fibroblasts cultured from the genital skin of 28 unrelated phenotypically normal men with idiopathic azoospermia or oligospermia. The amounts of androgen receptor were compared with those in genital skin fibroblasts from a variety of other subjects, including 10 men with azoospermia of known cause, 5 normal men, 28 subjects with disorders of androgen formation of metabolism of known cause, and 28 persons with documented disorders of the androgen receptor (testicular feminization and Reifenstein syndrome). The mean androgen receptor Bmax (amount of high affinity binding) was 12 fmol/mg protein or greater in 10 infertile men with azoospermia of known cause and in 6 infertile men with mild oligospermia. In fibroblasts from 1 to 4 individuals with severe oligospermia of unknown cause (less than 1 million/ml) and 8 of 18 subjects with idiopathic azoospermia, the androgen receptor Bmax was less than 12 fmol/mg protein. The mean value in these 9 men was not significantly different from that in subjects with testicular feminization or Reifenstein syndrome. Serum concentrations of testosterone and LH were normal in 6 of these 9 infertile men, and plasma production rates of testosterone were elevated in only 2 of the 6 men studied in whom the Bmax values in genital skin fibroblasts were less than 12 fmol/mg protein. We conclude that androgen resistance may be the cause of a significant fraction (40% or more) or idiopathic male infertility due to azoospermia or severe oligospermia, and that this disorder may not be manifested by a functional defect in the pituitary-testicular axis.     

Randomized placebo-controlled trial of testosterone replacement in men with mild Leydig cell insufficiency following cytotoxic chemotherapy

OBJECTIVE: Testosterone deficiency is associated with significant morbidity, and androgen replacement in overt hypogonadism is clearly beneficial. However, there are few data concerning the response to therapy in young men with mild testosterone deficiency. DESIGN AND PATIENTS: We have identified a cohort of 35 men, mean age 40.9 years, with mild Leydig cell dysfunction, defined by a raised LH level (LH >or= 8 IU/l) and a testosterone level in the lower half of the normal range or frankly subnormal (testosterone < 20 nmol/l), following treatment with cytotoxic chemotherapy for malignancy. Patients were assigned randomly to 12 months treatment with transdermal testosterone (n = 16) (Andropatch 2.5 mg patches, 1-2 patches per day) or placebo patches (n = 19) in a single blinded manner. MEASUREMENTS: Measurements of bone mineral density (BMD) and body composition were performed at baseline, 6 months and 12 months using single and dual energy X-ray absorptiometry (SXA, DXA). In addition, spinal BMD was assessed at baseline and 12 months by quantitative CT (QCT). Subjects were reviewed at 3-monthly intervals; at each visit blood was taken for measurement of testosterone, SHBG, LH, FSH, oestradiol, lipids and IGF-1 and patients completed three questionnaires which assessed energy levels, mood and sexual function. RESULTS: Total testosterone and calculated free testosterone increased significantly in the testosterone-treated group compared with the placebo-treated group (13.3 nmol/l and 342.9 pmol/l at baseline compared with 17.3 nmol/l and 454.8 pmol/l during the study period in the testosterone-treated group; P = 0.05 and P = 0.02, respectively). LH was suppressed into the normal range in 15 of the 16 testosterone-treated men and mean LH significantly reduced from 11.1 IU/l at baseline to 6.8 IU/l during the study. There was no significant change in BMD at the hip, spine or forearm and no change in fat or lean body mass. There was a significant reduction in physical fatigue in the testosterone-treated group compared with the placebo-treated group (P = 0.008) and a borderline improvement in activity score (P = 0.05). There were no significant effects of treatment on mood or sexual function. Neither oestradiol nor IGF-1 levels differed between the two groups during the study. There was no significant change in mean total cholesterol, HDL cholesterol or triglyceride levels, but there was a small, but significant reduction in LDL cholesterol levels in the testosterone-treated group compared with the placebo group (P = 0.02). CONCLUSIONS: These results suggest that testosterone therapy in young men with raised LH levels and low/normal testosterone levels does not result in significant changes in BMD, body composition, lipids or quality of life, apart from a reduction in physical fatigue and a small reduction in LDL cholesterol. This implies that mild hypogonadism defined on this basis is not of clinical importance in the majority of men, and that androgen replacement cannot be recommended for routine use in these patients.     

Male pseudohermaphroditism due to Leydig cell agenesia and absence of testicular LH receptors

OBJECTIVE: The aim of our study was to establish the definitive diagnosis in an adult patient with male pseudohermaphroditism in whom testicular feminization syndrome had been suspected at the age of 8, based on genetic, clinical and pathological studies. DESIGN: Hypothalamo-hypophysio-testicular function was assessed in vivo. Androgen mechanism of action and testicular gonadotrophin binding were studied in vitro. PATIENT: At the age of 33 the phenotype was almost completely feminine except for slight clitoral enlargement and posterior labial fusion. Internal genital duct derivatives were masculine except for a short vagina. Both testes were cryptorchid. MEASUREMENTS: LH and FSH were determined pre- and post-gonadectomy. Progesterone, 17-OH-progesterone, androstenedione, dehydroepiandrosterone testosterone (T) and oestradiol were determined basally in peripheral and spermatic blood post-hCG stimulation, and in peripheral blood after orchidectomy. Dihydrotestosterone (DHT) receptors and 5 alpha-reductase activity were determined in genital skin fibroblasts. Receptors for LH and FSH were determined in membrane preparations from both testes. RESULTS: LH was high (31 IU/l) and FSH (8 IU/ml) normal. T or steroid precursors were detected basally or after hCG stimulation in peripheral blood showing absence of testicular production. Spermatic venous blood steroid concentrations were consistent with slight T production, in accordance with testis histology which showed few Leydig-like cells among fibroblasts in the interstitial space. DHT specific binding capacity and affinity and 5 alpha-reductase activity were normal in genital skin fibroblasts. Gonadotrophin binding studies in testicular membranes confirmed the absence of LH specific binding, whereas FSH binding was higher than normal when expressed per mg of protein (27.0 vs 9.4 +/- 0.6 fmol/mg protein in controls), and lower than normal in both testes since patient's testicular weights were abnormally low. CONCLUSIONS: The patient was considered to have an almost complete form of Leydig cell agenesia/hypoplasia in which absence of specific LH binding correlated with total absence of differentiated Leydig cells and insensitivity of undifferentiated interstitial cells to LH stimulation.     

Dihydrotestosterone formation (5 alpha-reductase activity) in cultured human skin fibroblasts

Testosterone secreted from the testis is converted to dihydrotestosterone (DHT) in target tissues by 5 alpha-reductase and DHT exerts its action on the nucleus. Since skin is one of the target tissues of androgen we established a system for culturing human skin fibroblasts, and we investigated the conversion of testosterone to DHT in genital and nongenital skin fibroblasts obtained from males as well as from females. In our system, fibroblasts were incubated with 0.1 microM 1, 2-3H testosterone, and labeled metabolites were separated by thin layer chromatography. DHT formation was linear for 6 hours and the rate of DHT formation correlated with the growth phase of the fibroblasts. In the course of serial subculture, DHT formation did not change between the 3rd and 10th subculture in four cell strains. DHT formation in nongenital skin fibroblasts did not differ significantly between males and females. Fibroblasts obtained from male genital skin produced significantly greater amounts of DHT than those from male or female nongenital skin. Furthermore, DHT formation in genital skin fibroblasts did not differ between normal males and hypogonadal males. These data suggest that genital skin is the target tissue where testosterone strongly converts to DHT and the difference of male secondary sexual characteristic appearance between males and females may not depend on the sensitivity of the target tissues to androgen but on the secretion rate of androgen.     

A mutation of the androgen receptor associated with partial androgen resistance, familial gynecomastia, and fertility

A family is described in which gynecomastia and undervirilization in five men (four of whom have fathered children) were inherited in a manner compatible with an X-linked defect. Three members from whom blood could be obtained had supranormal serum testosterone and normal LH and FSH levels. One man had severe oligospermia with decreased motility, and one had normal sperm density and motility. In fibroblasts cultured from genital skin biopsies from two of the men, the levels of androgen receptor and affinity of binding of receptor to dihydrotestosterone were normal. However, androgen binding in fibroblast monolayers was thermolabile, up-regulation of receptor levels did not occur after prolonged incubation of monolayers with dihydrotestosterone or methyltrienolone, and dissociation rates at 37 C were increased with the synthetic androgen mibolerone. In addition, in cytosol preparations the androgen receptor protein was unstable. This disorder probably represents the most subtle functional abnormality of androgen receptor characterized to date, since it is compatible with normal male phenotypic development and in some affected men with fertility. It follows that infertility is not an invariable feature of androgen resistance as we previously suggested.     

Complete androgen insensitivity caused by a new frameshift deletion of two base pairs in exon 1 of the human androgen receptor gene.

We describe a novel mutation in exon 1 of the androgen receptor gene in a patient with complete androgen insensitivity (CAIS). Endocrine findings were typical for androgen insensitivity (testosterone serum levels in the upper limit of normal males and increased LH serum concentrations). Biochemical investigations in cultured genital skin fibroblasts of the patient showed a normal 5alpha-reductase activity but a complete absence of androgen binding. Western blot analysis revealed no detectable protein product. Sequence analysis of the entire coding region of the androgen receptor gene resulted in the identification of a 2-bp deletion in codon 472, causing frameshift and introduction of a premature stop codon 27 codons downstream of the mutation.     

Dihydrotestosterone accumulation in genital skin fibroblasts derived from elderly men with prostatic hyperplasia.

The conversion of testosterone to dihydrotestosterone (DHT) by 5 alpha-reductase and the interconversion between DHT and 5 alpha-Androstane-3 alpha,17 beta-diol (3 alpha-diol) by 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR) were studied in fibroblasts derived from the genital skin of 15 prepubertal boys (2-10 yr), 17 young men (20-40 yr), 13 elderly men (60-78 yr) without clinically evident prostatic pathology, and 17 elderly men (61-88 yr) with benign prostatic hyperplasia (BPH). Respective DHT formations from testosterone (5 alpha-reduction) and 3 alpha-diol (3 alpha-HSOR oxidation) were not different among genital skin fibroblasts of the 4 groups. However, DHT degradation to 3 alpha-diol (3 alpha-HSOR reduction) was significantly lower in fibroblasts from elderly men with BPH than in those from the prepubertal boys (P less than 0.01), the young men (P less than 0.01), and the elderly men without BPH (P less than 0.05). 3 beta-HSOR reduction in fibroblasts of the BPH group was significantly lower (P less than 0.05) than in those of the elderly men without BPH; however, it did not differ from values for the prepubertal boys and the young men. (3 alpha + 3 beta)-HSOR reduction was also significantly lower (P less than 0.05) in the BPH group than respective values of the three other groups. These results indicate that DHT accumulation may occur in genital skin fibroblasts from elderly men with BPH, resulting from a shift in the overall balance of androgen metabolism, which favors the net formation of DHT.     

Novel point mutation in the splice donor site of exon-intron junction 6 of the androgen receptor gene in a patient with partial androgen insensitivity syndrome

Androgen receptor (AR) gene mutations have been shown to cause androgen insensitivity syndrome with altered sexual differentiation in XY individuals, ranging from a partial insensitivity with male phenotype and azoospermia to a complete insensitivity with female phenotype and the absence of pubic and axillary sexual hair after puberty. In this study we present an 11-yr-old XY girl, with clinical manifestations peculiar for impaired androgen biological action, including female phenotype, blind-ending vagina, small degree of posterior labial fusion, and absence of uterus, fallopian tubes, and ovaries. At the time of the diagnosis the patient had a FSH/LH ratio according to the puberal stage, undetectable 17beta-estradiol, and high levels of testosterone (80.1 ng/mL). After bilateral gonadectomy, performed at the age of 11 yr, histological examination showed small embryonic seminiferous tubules containing prevalently Sertoli cells and occasional spermatogonia together with abundant fibrous tissue. Molecular study of the patient showed a guanine to thymine transversion in position +5 of the donor splice site in the junction between exon 6 and intron 6 of the AR gene. The result of RT-PCR amplification of the AR messenger ribonucleic acid from cultured genital skin fibroblasts of the patient suggests that splicing is defective, and intron 6 is retained in most of the receptor messenger ribonucleic acid molecules. We show by immunoblotting that most of the expressed protein lacks part of the C-terminal hormone-binding domain, and a small amount of normal receptor is observed. This is probably responsible for the reduced binding capacity in genital skin fibroblasts of the patient. The molecular basis of the alteration in this case is a novel, uncommon mutation, leading to a phenotype indicative of a partial androgen insensitivity syndrome, Quigley's grade 5.     

Androgen receptor in cultured human testicular fibroblasts

Androgen receptors and 5 alpha-reductase activity were studied previously in genital skin fibroblasts cultured from normal subjects and patients with abnormalities of sex differentiation. We have now identified and characterized the androgen receptor in cultured human testis fibroblasts (HTF). HTF possess specific receptor proteins for androgens and translocate the receptor-steroid complex to nuclei. Approximately 50% of total cell binding was within nuclei, and 60-70% of nuclear binding was extracted by 0.5 M KCl (1 h; 0 C). Specific binding of dihydrotestosterone (DHT) was absent in HTF cultured from three patients with receptor-negative complete androgen insensitivity. 5 alpha-Reductase activity was very low (less than 100 pg 5 alpha-reduced products/micrograms DNA X h) in HTF after incubation with 200 nM [3H] testosterone (T). Based on this finding, androgen receptor binding of T was studied and resulted in a maximum binding capacity similar to that for DHT, but with a slightly lesser binding affinity (Kd). Binding to the receptor in HTF was specific for androgens (DHT, T, and R1881). [3H]DHT (2 nM) binding in the presence of 100 nM radioinert steroid was decreased by DHT (87%), R1881 (82%), and T (72%), but less with estradiol (53%), progesterone (31%), androstanediol (23%), and dexamethasone (10%). The androgen receptor in HTF was characterized as a macromolecule which sedimented at 4-5S on 0.4 M KCl sucrose density gradients and eluted as three high mol wt peaks on Sephacryl S-300 chromatography. Low but detectable aromatase activity was present in HTF and had the characteristics of being induced by glucocorticoid and having a Km similar to that of aromatase activity for genital skin fibroblasts. In summary, specific androgen receptors are present in HTF, and their characteristics are similar to those previously described for genital skin fibroblasts.     

Variable androgen receptor levels in infertile men

Labeled methyltrienelone was used to determine androgen receptor (AR) levels in cultured pubic skin fibroblasts in 40 infertile men with primary seminiferous tubule disorders and 18 normal men. LH pulse patterns and mean serum LH levels were also determined by blood sampling at 10-min intervals for 6 h. The infertile men and the normal men had similar mean receptor levels [mean, 28.1 +/- 2.0 (+/- SEM) and 24.8 +/- 1.8 fmol/mg protein, respectively]. However, 5 men with chromosomal disorders had a higher mean AR level (41.3 +/- 6.2 fmol/mg protein) than the normal men, and 5 of the remaining infertile men (14.2%) had receptor levels that were less than the minimum value in normal men. In men with idiopathic oligospermia, 19.0% had low receptor levels. Although mean serum FSH and testosterone levels were similar in the infertile men with low AR levels and in the normal men, mean LH levels were significantly elevated in this group (7.1 vs. 3.6 IU/L), the higher values being a result of increased LH pulse amplitude (mean, 5.6 vs. 2.8 IU/L). The LH-testosterone product (an index of androgen resistance) was also elevated in these men. When infertile men with low AR levels were matched with infertile men with normal receptor levels, the mean LH values were significantly elevated in the former, as was the LH-testosterone product. Testosterone values were similar in the two groups of men. After excluding subjects with chromosomal disorders, there were no significant correlations between AR levels and other indices of androgen action, such as semen volume, seminal fructose, or sex hormone-binding globulin levels. We conclude that AR levels are higher in patients with severe testicular failure associated with X-chromosome disorders. Also, AR defects were found in 19.0% of infertile men with idiopathic oligospermia. Finally, elevation of mean LH levels in men with seminiferous tubule disorders may reflect resistance to androgen action.     

Crystalline dihydrotestosterone implants in the lateral septum of male rats. A positive effect on LH and FSH.

Previous investigations in our laboratory have shown that testosterone implanted into the lateral septum in male rats increases LH and FSH secretion. However, it was unclear whether the effect of testosterone was direct via androgen receptor, or indirect via the estrogen receptor after conversion by aromatization to estradiol. To answer this question, we implanted either testosterone or the non-aromatizable androgen 5 alpha-dihydrotestosterone (DHT), into the lateral septum of adult male rats and measured plasma levels of LH and FSH by radioimmunoassay 2 days after implantation. Both testosterone and DHT significantly increased the plasma LH and FSH concentrations. Mean concentration of LH in control animals was 0.21 +/- 0.06 ng/ml, a figure that increased to 0.7 +/- 0.12 and 0.55 +/- 0.1 ng/ml after DHT or testosterone implantation respectively. Mean concentration of FSH in control animals was 1.5 +/- 0.3 ng/ml; this figure increased to 3 +/- 0.3 and 2.9 +/- 0.3 ng/ml after DHT or testosterone implantation. Neither plasma DHT (64.0 +/- 5.6 vs. 52 +/- 5 ng/100ml) nor plasma testosterone levels (4.1 +/- 0.38 vs. 3.3 +/- 0.18 ng/ml) were significantly affected by the implants. We conclude that androgens independently of conversion to estrogen acting in the lateral septum facilitates the release of LH and FSH.     

Regulation of androgen receptor and 5 alpha-reductase in the skin of normal and hirsute women

The hormonal activity of androgens is mediated in target cells, particularly in human skin, by two kinds of proteins: the androgen receptor and the enzyme 5 alpha-reductase. In well differentiated androgen target cells, 5 alpha-reductase achieves the transformation of testosterone (T) into dihydrotestosterone (DHT), a more active androgen than T, because of its higher affinity for the receptor. In other words, 5 alpha-reductase acts as an amplifier of the androgen signal but is not absolutely required for androgen action. Regarding the regulation of the androgen receptor, minimal information is available. However, in genital skin, the receptor seems to be predominantly localized in the cytosolic compartment before puberty in males and in the nuclear compartment after puberty. In hirsute patients, recent data on genital skin fibroblasts do not show significant differences between the binding capacity of fibroblasts from normal and hirsute women whereas there is no difference between normal men and women. 5 alpha-Reductase activity seems to be a very important step in the processes involved in androgen action. While 5 alpha-reductase activity present in the skin of external genitalia does not seem to be androgen dependent, this is not the case for the enzyme located in pubic skin. In this area, a sex difference between males and females may be observed both in skin homogenates and in cultured fibroblasts. In addition DHT added to a medium of pubic skin fibroblasts is capable of increasing 5 alpha-reductase activity. This increase is not observed when cyproterone acetate is added to the medium and in patients with testicular feminization syndrome without receptors. Pubic 5 alpha-reductase activity is an androgen receptor mediated phenomenon. In patients with hirsutism, and particularly idiopathic hirsutism, 5 alpha-reductase activity is high without an increase in circulating androgens. This may be observed both in pubic skin homogenates and in cultured fibroblasts. Thus, an excess of skin 5 alpha-reductase activity may be considered as a cause of hirsutism but both the exact level of the abnormality in the regulation of the enzyme and its genetic control remain to be elucidated.     

In men older than 70 years, total testosterone remains stable while free testosterone declines with age. The Health in Men Study

OBJECTIVE: An age-related decline in serum total and free testosterone concentration may contribute to ill health in men, but limited data are available for men > 70 years of age. We sought to determine the distribution and associations of reduced testosterone concentrations in older men. DESIGN: The Health in Men Study is a community-representative prospective cohort investigation of 4263 men aged > or = 70 years. Cross-sectional hormone data from 3645 men were analysed. METHODS: Early morning sera were assayed for total testosterone, sex hormone binding globulin (SHBG) and LH. Free testosterone was calculated using the Vermeulen method. RESULTS: Mean (+/- s.d.) serum total testosterone was 15.4 +/- 5.6 nmol/l (444 +/- 162 ng/dl), SHBG 42.4 +/- 16.7 nmol/l and free testosterone 278 +/- 96 pmol/l (8.01 +/- 2.78 ng/dl). Total testosterone correlated with SHBG (Spearman's r = 0.6, P < 0.0001). LH and SHBG increased with age (r = 0.2, P < 0.0001 for both). Instead of declining, total testosterone increased marginally (r = 0.04, P = 0.007) whilst free testosterone declined with age (r = -0.1, P < 0.0001). Free testosterone was inversely correlated with LH (r = -0.1, P < 0.0001). In multivariate analyses, increasing age, body mass index (BMI) and LH were associated with lower free testosterone. CONCLUSIONS: In men aged 70-89 years, modulation of androgen action may occur via an age-related increase in SHBG and reduction in free testosterone without a decline in total testosterone concentration. Increasing age, BMI and LH are independently associated with lower free testosterone. Further investigation would be required to assess the clinical consequences of low serum free testosterone, particularly in older men in whom total testosterone may be preserved.     

Pharmacokinetics,safety and tolerability of three dosage regimens of buccal adhesive testosterone tablets in healthy men suppressed with leuprorelin

We used a randomised, double-blind, crossover design to evaluate the pharmacokinetics, safety and tolerability of three doses of buccal adhesive testosterone tablets (BATT). Twenty-four healthy men, whose endogenous testosterone was suppressed to 相似文献   

QUANTITATIVE AND QUALITATIVE CHANGES IN LH SECRETION FOLLOWING PULSATILE GnRH THERAPY IN A MAN WITH IDIOPATHIC HYPOGONADOTROPHIC HYPOGONADISM

The pattern of bioactive and immunoreactive LH secretion before and during pulsatile GnRH therapy (18 micrograms/90 min) in a hypogonadotrophic hypogonadal male has been studied. Before treatment the patient was azoospermic and had low testosterone (1.2 nmol/l) with low and apulsatile immunoreactive LH (1.9 +/- 0.2 IU/l) and FSH (1.4 +/- 1.9 IU/l) levels. There was no detectable LH bioactivity. During the first 24 h of GnRH therapy there was a small increase in immunoreactive (5.4 +/- 0.8 IU/l) and bioactive (6.7 +/- 1.3 IU/l) LH, with an irregular pattern and little effect on testosterone production (2.2 nmol/l). Within 1 week of treatment both bioactive (30.5 +/- 6.8 IU/l) and immunoreactive (13.6 +/- 1.5 IU/l) LH levels were above the normal range and the pattern of secretion was pulsatile. The bioactive to immunoreactive (B:I) LH ratios within the pulses (2.6 +/- 0.3) were higher (P less than 0.01) than between pulses (1.97 +/- 0.1) and the testosterone concentration (17.8 +/- 2.1 nmol/l) was now normal. At one month LH secretion was similar and testosterone pulses of high amplitude were evident corresponding to high-amplitude bioactive LH pulses. By 3 months mature spermatozoa (1.3 x 10(6)/ml) were seen in the patient's semen. The pattern of LH secretion was pulsatile but the levels of bioactive (13.1 +/- 3.6 IU/l) and immunoreactive (9.5 +/- 1.3 IU/l) LH decreased towards the normal range reflecting maturation of the testicular feedback control at the pituitary level. This effect was more pronounced on bioactive rather than immunoreactive LH secretion (57% vs 32% relative decrease). At 6 months LH levels were similar and the sperm count was normal (34 x 10(6)/ml).     

Phenotypic diversity and testosterone-induced normalization of mutant L712F androgen receptor function in a kindred with androgen insensitivity

Molecular causes of phenotypic diversity in androgen insensitivity syndrome, occurring even in the same family, have rarely been identified. We report on a family with four affected individuals, three brothers (B1-3) and their uncle, displaying strikingly different external genitalia: B1, ambiguous; B2, severe micropenis; B3, slight micropenis; and uncle, micropenis and penoscrotal hypospadias. All had been assigned a male gender. We detected the same L712F mutation of the androgen receptor (AR) gene in each subject. Methyltrienolone binding on cultured genital skin fibroblasts of B2 suggested moderate impairment of the ligand-binding domain [maximal binding capacity, 38.2 fmol/mg protein (normal); Kd, 0.21 nmol/L; normal range, 0.03-0.13 nmol/L]. In trans-activation assays, the mutant 712F-AR showed considerable deficiency at low concentrations of testosterone (0.01-0.1 nmol/L) or dihydrotestosterone (0.01 nmol/L). Remarkably, this could be fully neutralized by testosterone concentrations greater than 1.0 nmol/L. Hence, the 712F-AR could switch its function from subnormal to normal within the physiological concentration range of testosterone. This was reflected by an excellent response to testosterone therapy in B1, B2, and the uncle. Taking into account the well documented individual and time-dependent variation in testosterone concentration in early fetal development, our observations clearly illustrate the potential impact of varying ligand concentrations for distinct cases of phenotypic variability in androgen insensitivity syndrome.