Osteopenia as a feature of the androgen insensitivity syndrome

OBJECTIVE The syndrome of androgen insensitivity, a paradigm of a hormone resistance syndrome, manifests as failure of masculinization despite normal or high concentrations of serum testosterone. The defect in these 46 XY patients resides in the androgen receptor gene, with consequent defective androgen action and abnormal sexual differentiation. We sought to evaluate whether the adverse sequelae of androgen resistance may extend to skeletal tissue by measuring bone mineral density In SIX patients with androgen Insensitivity. DESIGN A cross-sectional retrospective study. MEASUREMENTS Bone mineral density was measured by means of a Dexa (Hologic QDR 1000 scanner). The diagnosis of androgen Insensitivity was confirmed in each patient by karyotype and assay of sex hormones. RESULTS The five adult patients with androgen insensitivity had been exposed to both defective androgen action and variable periods of oestrogen deficiency. The latter resulted from the low circulating oestrogen concentrations (for premenopausal females) before gonadectomy and inadequate oestrogen replacement afler gonadectomy. All five adults with androgen insensitivity had osteopenia in both the lumbar spine (T-score ?1.52 to ?3.85) and femoral neck (T- score ?1.34 to ?4.91). CONCLUSIONS Osteopenia in patients with androgen insensitivity may relate to defective androgen action, oestrogen deficiency or a combination of the two. These observations have implications for the management of patients with androgen insensitivity and may provide insight into the effects of androgens on the female as well as the male skeleton.     

雄激素受体基因新突变致雄激素不敏感综合征

目的 分析2例雄激素不敏感综合征患者及其家系的临床及分子遗传学.方法 收集2例雄激素小敏感综合征患者的临床资料,从患者及其家系成员的外周血单个核细胞抽提基因组DNA,应用PCR扩增雄激素受体基因并直接测序,明确患者及其父母基因有无突变.结果 患者1表现为女性外生殖器、单侧乳房发育、原发性闭经、阴毛腋毛缺如.患者2表现为男性化不全,体毛稀少、双侧乳房发育、尿道下裂.基因检测证实患者1雄激素受体基因第2号外显子第579位密码子点突变(S579N),并证实为一新突变.患者2第5号外显子第747位密码子点突变(V747M).结论 该2例雄激素受体不敏感综合征系分别由雄激素受体基因S579N及V747M所致,其中S579N突变尚未见文献报道.     

Genotype versus phenotype in families with androgen insensitivity syndrome

Androgen insensitivity syndrome encompasses a wide range of phenotypes, which are caused by numerous different mutations in the AR gene. Detailed information on the genotype/phenotype relationship in androgen insensitivity syndrome is important for sex assignment, treatment of androgen insensitivity syndrome patients, genetic counseling of their families, and insight into the functional domains of the AR. The commonly accepted concept of dependence on fetal androgens of the development of Wolffian ducts was studied in complete androgen insensitivity syndrome (CAIS) patients. In a nationwide survey in The Netherlands, all cases (n = 49) with the presumptive diagnosis androgen insensitivity syndrome known to pediatric endocrinologists and clinical geneticists were studied. After studying the clinical phenotype, mutation analysis and functional analysis of mutant receptors were performed using genital skin fibroblasts and in vitro expression studies. Here we report the findings in families with multiple affected cases. Fifty-nine percent of androgen insensitivity syndrome patients had other affected relatives. A total of 17 families were studied, seven families with CAIS (18 patients), nine families with partial androgen insensitivity (24 patients), and one family with female prepubertal phenotypes (two patients). No phenotypic variation was observed in families with CAIS. However, phenotypic variation was observed in one-third of families with partial androgen insensitivity resulting in different sex of rearing and differences in requirement of reconstructive surgery. Intrafamilial phenotypic variation was observed for mutations R846H, M771I, and deletion of amino acid N682. Four newly identified mutations were found. Follow-up in families with different AR gene mutations provided information on residual androgen action in vivo and the development of the prepubertal and adult phenotype. Patients with a functional complete defective AR had some pubic hair, Tanner stage P2, and vestigial Wolffian duct derivatives despite absence of AR expression. Vaginal length was functional in most but not all CAIS patients. The minimal incidence of androgen insensitivity syndrome in The Netherlands, based on patients with molecular proof of the diagnosis is 1:99,000. Phenotypic variation was absent in families with CAIS, but distinct phenotypic variation was observed relatively frequent in families with partial androgen insensitivity. Molecular observations suggest that phenotypic variation had different etiologies among these families. Sex assignment of patients with partial androgen insensitivity cannot be based on a specific identified AR gene mutation because distinct phenotypic variation in partial androgen insensitivity families is relatively frequent. In genetic counseling of partial androgen insensitivity families, this frequent occurrence of variable expression resulting in differences in sex of rearing and/or requirement of reconstructive surgery is important information. During puberty or normal dose androgen therapy, no or only minimal virilization may occur even in patients with significant (but still deficient) prenatal virilization. Wolffian duct remnants remain detectable but differentiation does not occur in the absence of a functional AR. In many CAIS patients, surgical elongation of the vagina is not indicated.     

Phenotypic features, androgen receptor binding, and mutational analysis in 278 clinical cases reported as androgen insensitivity syndrome

Androgen insensitivity syndrome (AIS) is the most common single entity that results in male under-masculinization, but large cohort studies of AIS have rarely been performed. Over the last decade, nationwide cooperation between pediatric endocrinologists in the United Kingdom has allowed the creation of a database of cases of intersex and ambiguous genitalia where detailed clinical information on every notified case has been collected via a questionnaire. Among the 816 entries recorded by January 1999, there were 105 clinically diagnosed cases of complete AIS (CAIS) and 173 cases of partial AIS (PAIS). A masculinization score was devised by scoring the external phenotype, and a score of 12 represented normal masculinization. Androgen receptor (AR) binding was determined by studying binding capacity (Bmax) and receptor affinity (K(d)), and cases were classified as either zero, abnormal, or normal binding. Mutation screening of all eight exons of the AR gene was performed by single-strand conformational polymorphism analysis, followed by direct DNA sequencing. All cases of PAIS presented within the first month of birth. The median age at presentation of children with CAIS was 1 yr (P10,P90: 0.1,10.4). The testes were palpable in the labioscrotal folds or the inguinal region in 77% and 41% of cases of CAIS and PAIS, respectively. There was marked overlap between the masculinization score of those children with PAIS reared as girls [2.5(P10,P90:1, 6)] and those reared as boys [3(P10,P90:2, 7.5)]. Gonadectomy was performed prepubertally in 66% and postpubertally in 29% of the cases of CAIS. The median age of the latter group was older at 14 yr (P10,P90:0.1,18). No cases of malignancy or carcinoma in situ were reported in the 121 cases of AIS where histology results were available. Biochemical endocrine investigations were reported to have been performed in a greater number of cases of PAIS than CAIS (98% vs. 48%). AR binding was abnormal in 44 of 51 (86%) and 40 of 113 (35%) cases of CAIS and PAIS, respectively. Zero binding was encountered in 29 of 43 (67%) and 1 of 55 (2%) cases of CAIS and PAIS, respectively. Mutational analysis of the AR gene, performed in 102 index cases was positive in 57 of 69 (83%) cases of CAIS and 12 of 43 (28%) cases of PAIS. In 24 of these cases, the mutation identified was novel. The mutations in PAIS cases were all missense, whereas in CAIS the mutations were more diverse. AR binding was only normal in 3 of 69 mutation-positive cases. In the PAIS group, mutation-positive cases had a significantly higher Kd and Bmax compared to the mutation negative cases. The clinical diagnosis of AIS can be confirmed in a significant number of cases by a combination of androgen-binding studies and mutational analysis. There is some correlation between the phenotypic features and the abnormalities discovered on mutational analysis of the AR gene, but there is a need to improve this further by developing optimal bioassays of AR function. The phenotypic heterogeneity among clinically diagnosed cases of AIS emphasizes the need for appropriate comprehensive evaluation of male under-masculinization.     

Hormonal management of complete androgen insensitivity syndrome from adolescence onward

Complete androgen insensitivity syndrome (CAIS) represents a main disorder of sex development. Women with CAIS may have their gonads removed before, during or after adolescence, thus requiring hormonal replacement therapy to induce puberty and/or maintain secondary sexual characteristics, to optimize bone mass accrual, and to promote physical and social well-being. Usually estrogens are used for this purpose, but formulations and doses should be better defined in multicentric prospective studies. Some women started testostosterone as hormonal replacement therapy, but this practice remains anecdotal. Bone health remains a crucial aspect in the management of persons with CAIS, but few sound data are available to guide clinical practice.     

Incidence of intratubular germ cell neoplasia in androgen insensitivity syndrome

Gonadal histology was investigated by means of conventional microscopy in 6 patients with complete androgen insensitivity syndrome, in 11 with incomplete androgen insensitivity syndrome, and in 3 with 5 alpha-reductase syndrome. Twelve subjects were prepubertal and 8 pubertal. In all patients gonadal tissue was removed as a prophylactic measure and no patients gave rise to any clinical suspicion of a tumour. Eight patients with incomplete androgen insensitivity syndrome, 5 of whom (62.5%) were prepubertal, showed intratubular germ cell neoplasia and in 6 of them it was bilateral. Histochemical and immunohistochemical analysis showed considerable agreement between atypical morphological aspects and positive response to Schiff's periodic acid and to staining with the anti-placenta alkaline phosphatase antibody. Our patients were characterized by one of the highest reported incidences of intratubular germ cell neoplasia, particularly at prepubertal age. These findings would seem to indicate that a rethink is needed concerning the general opinion that patients with androgen intensivity syndrome have practically no risk of developing malignancy, and that orchidectomy is not advisable before puberty is completed.     

Discordant measures of androgen-binding kinetics in two mutant androgen receptors causing mild or partial androgen insensitivity, respectively

We have characterized two different mutations of the human androgen receptor (hAR) found in two unrelated subjects with androgen insensitivity syndrome (AIS): in one, the external genitalia were ambiguous (partial, PAIS); in the other, they were male, but small (mild, MAIS). Single base substitutions have been found in both individuals: E772A in the PAIS subject, and R871G in the MAIS patient. In COS-1 cells transfected with the E772A and R871G hARs, the apparent equilibrium dissociation constants (Kd) for mibolerone (MB) and methyltrienolone are normal. Nonetheless, the mutant hAR from the PAIS subject (E772A) has elevated nonequilibrium dissociation rate constants (k(diss)) for both androgens. In contrast, the MAIS subject's hAR (R871G) has k(diss) values that are apparently normal for MB and methyltrienolone; in addition, the R871G hAR's ability to bind MB resists thermal stress better than the hAR from the PAIS subject. The E772A and R871G hARs, therefore, confer the same pattern of discordant androgen-binding parameters in transfected COS-1 cells as observed previously in the subjects' genital skin fibroblasts. This proves their pathogenicity and correlates with the relative severity of the clinical phenotype. In COS-1 cells transfected with an androgen-responsive reporter gene, trans-activation was 50% of normal in cells containing either mutant hAR. However, mutant hAR-MB binding is unstable during prolonged incubation with MB, whereas normal hAR-MB binding increases. Thus, normal equilibrium dissociation constants alone, as determined by Scatchard analysis, may not be indicative of normal hAR function. An increased k(diss) despite a normal Kd for a given androgen suggests that it not only has increased egress from a mutant ligand-binding pocket, but also increased access to it. This hypothesis has certain implications in terms of the three-dimensional model of the ligand-binding domain of the nuclear receptor superfamily.     

Molecular biology of androgen insensitivity

Androgen insensitivity syndrome (AIS) is the most common specific cause of 46,XY disorder in sex development. The androgen signaling pathway is complex but so far, the only gene linked with AIS is the androgen receptor (AR). Mutations in the AR are found in most subjects with complete AIS but in partial AIS, the rate has varied 28-73%, depending on the case selection. More than 400 different mutations in AR leading to AIS have been reported. Most mutations are missense substitutions located in the ligand binding domain of the receptor. However, when systematically screened, a substantial amount of mutations can be detected also in the N-terminal domain encoded by exon 1. Within this exon lie two trinucleotide, CAG and GGN repeat regions which are polymorphic in length. Their role in androgen insensitivity is somewhat unclear. Recent advances in protein modeling have resulted in better understanding of the mechanism of known AR mutations.     

Complete form of androgen insensitivity syndrome in Brazilian patients due to P766A mutation in the androgen receptor

Androgen insensitivity syndrome (AIS) is a rare X-linked disorder, caused by mutations in the androgen receptor gene (AR), associated with a variety of phenotypes in 46,XY individuals. We studied two 23 year-old twin-sisters with female social sex referred due to primary amenorrhea, who exhibited bilateral palpable gonads in the inguinal region and a 46,XY karyotype. The uterus was absent in pelvic sonograms. Basal LH levels were elevated (35 and 42 U/L), with normal FSH (7.9 and 7.8 U/L) and high testosterone levels (1330 and 1660 ng/dl). The molecular analysis identified a missense mutation in exon 5 of AR gene that changed a proline to an alanine at position 766 of the protein. Proline 766 is a highly conserved amino acid in the AR of several species and is located in the androgen binding domain.     

Point mutations detected in the androgen receptor gene of three men with partial androgen insensitivity syndrome

OBJECTIVE Determine the sequence of the androgen receptor gene in men with impaired responsiveness to androgens in order to identify the molecular basis of their under-virilization. DESIGN Blood samples were used as the source of genomic DNA. Portions of the androgen receptor gene were amplified by polymerase chain reaction and sequenced. PATIENTS Samples were obtained from three patients and five normal fertile controls. Patients were all 46 XY and were undervirilized with ambiguous external genitalia, gynaecomastla and infertility. MEASUREMENTS Total cellular DNA was purified from peripheral blood leucocytes. Pairs of ollgonucleotide primers designed to flank the individual exons of the androgen receptor gene were synthesized. The specific regions of the androgen receptor were amplified from the samples of cellular DNA by polymerase chain reaction. Amplified DNA was purified, sequenced and compared to the published sequence. RESULTS In all three patients point mutations in the androgen receptor gene were detected but no defects were detected in samples from normal controls. In two of the patients, an identical single nucleotide change from G to T was detected. This nucleotide was within the codon for amino acid 866 and would change it from valine to leucine. Amino acid 866 is found within an area of the steroid binding domain thought to be involved in receptor dimerization. Within the repetitive sequence of exon I patient 1 had 21 glutamine residues and patient 2 had 25. In the third patient a single change of G to A would result in incorporation of lysine in place of a conserved arginine residue at position 607 within the second zinc finger of the DNA binding domain. The sequence of the androgen receptor gene of the mother of the third patient revealed her to be heterozygous for the same defect. CONCLUSION Patients 1 and 2 are unrelated although they have an identical point mutation in their androgen receptor gene. A patient with complete androgen insensitivity syndrome has been reported to have a defect at the same position causing the amino acid substitution of methlonine for valine. Therefore we confirm that the nature of the amino acid change in the peptide sequence of the androgen receptor as well as its location within the protein, can have a profound effect on the phenotypic severity of androgen resistance. Studies on mutated receptors from individuals with a wide range of degrees of androgen resistance may enable us to construct a map of the key amino acids in the different domains of the protein.     

Novel missense mutation in the P-box of androgen receptor in a patient with androgen insensitivity syndrome

Mutations in the X-linked AR gene cause androgen insensitivity syndrome (AIS) by impairing androgen-dependent male sex differentiation to various degree. Here we describe a partial AIS patient with confliction with the assigned female sex. Although the patient was noticed to have ambiguous genitalia at birth, the patient was reared as a female with no medical intervention. At the age of 31 years, the patient visited us because the patient was dissatisfied with the assigned female sex. The patient was treated with systemic testosterone and topical dihydrotestosterone, but the external genitalia responded only minimally to the treatment. The genetic analysis revealed a novel missense K580R mutation in the P-box of the DNA-binding domain of androgen receptor, which was the first missense mutation shared by AIS and prostate cancer. Although the best predictor of the adult gender identity is documented to be the initial gender assignment in patients with partial AIS as well as those with complete AIS, deciding gender assignment for infants with partial AIS is still challenging.     

Coexistence of Kallmann syndrome and complete androgen insensitivity in the same patient

Kallmann syndrome (KS) is a developmental disease that combines hypogonadotropic hypogonadism and anosmia/hyposmia. Other congenital abnormalities may also coexist. This present report describes two sisters, aged 13 and 12 years, born from Lebanese consanguineous parents. The two sisters have complete androgen insensitivity (normal female appearance and an XY karyotype) due to a novel mutation, a C-to-G transversion in intron 2 of the androgen receptor gene, resulting in an aberrant splicing leading to an insertion of 66 nucleotides in the mRNA. In addition, the older sister has KS, together with synkinesia and multiple skeletal abnormalities, mainly kyphosis, vertebral abnormalities, and short right hand and feet. Her testosterone, FSH and LH levels were very low compared with her younger sister. No mutation in the KAL1 and FGFR1/KAL2 genes were found. This unique report raises the possibility of an autosomal recessive or X-linked form of KS with new phenotypic expression.     

Morris syndrome: description of a case characterized by partial androgen insensitivity

The Morris syndrome is a X-linked recessive condition due to a complete or partial insensitivity to androgens, resulting in a failure of normal masculinization of the external genitalia in chromosomally male individuals. This failure of virilization can be either complete or partial depending on the amount of residual androgen receptor function. The phenotype of individuals with partial androgen insensitivity syndrome may range from mildly virilized female external genitalia to mildly undervirilized male external genitalia. We describe a case of Partial Androgen Insensitivity Syndrome in a 21-year-old patient with a 46, XY karyotype, bilateral inguinal masses, clitoral enlargement and partial posterior labial fusion. Surgical care consisted of bilateral orchiectomy and plastic surgery of external genitalia. The patient underwent estrogen replacement therapy.     

Complete androgen insensitivity syndrome characterized by increased concentration of a normal androgen receptor in genital skin fibroblasts

Two siblings with the classical phenotype of complete androgen insensitivity syndrome (CAIS) and increased total cellular androgen receptor concentrations in genital skin fibroblasts (GSF) are described. Testosterone biosynthesis was normal, and there was no evidence of 5 alpha-reductase deficiency. Specific binding of [3H]dihydrotestosterone ([3H]DHT) in GSF was 7 SD above the mean value in normal fibroblast strains [maximum binding, 775 +/- 185 X 10(-18) mol/micrograms DNA (mean +/- SD)]. Binding at 40 C was stable, and the androgen-receptor complex dissociated at a normal rate (t1/2, 85 min). The androgen-receptor complex from GSF cytosol sedimented at 5-6S on sucrose density gradients in the presence of sodium molybdate. In a whole cell binding assay, the percentage of [3H]DHT that bound to a crude nuclear pellet was 60%. Preincubation of GSF with 2 nM [3H]DHT for 20 h before the standard 1-h whole cell binding assay produced a further augmentation in elevated total cellular androgen receptor concentrations. A new variant of CAIS is described which is characterized by an increased concentration of androgen receptors that appear to be quantitatively and qualitatively normal. Augmentation of the receptor by androgen suggests that the gene coding for the androgen receptor is intact and does not account for the androgen insensitivity.     

Complete androgen insensitivity syndrome: a novel mutation in a Tunisian family

INTRODUCTION: Complete androgen insensitivity is a rare syndrome. It is caused by a mutation in the androgen receptor gene. We describe a novel mutation in exon 1. MATERIALS AND METHODS: We report the case of a 29 year-old girl with complete androgen insensitivity syndrome discovered during the exploration of a primary amenorrhoea. The family investigation revealed two other cases. RESULTS: The diagnosis was oriented by the clinical and the biological features and confirmed by the molecular study. A new mutation of the androgen receptor gene, as a deletion in exon 1 not described previously, was identified. CONCLUSION: Through these cases, clinical, hormonal and histological particularities were analysed.     

A new mutation of the androgen receptor, P817A, causing partial androgen insensitivity syndrome: in vitro and structural analysis

Androgen insensitivity syndrome (AIS) is an X-linked disease caused by mutations in the androgen receptor (AR) resulting in various degrees of defective masculinization in 46,XY individuals. In the present study, we describe a novel mutation in exon 7 of the AR gene in an Egyptian patient with partial AIS (PAIS). Sequencing analysis of the AR gene revealed a novel missense mutation, P817A, within the ligand-binding domain (LBD). This is the first report of a mutation within the short amino acid motif (codons 815-817) of the beta-strand lying between helices H8 and H9 of the AR LBD. The functional defects of the mutated protein were characterized by in vitro study and included significantly decreased ligand-binding affinity and impaired transactivation potential. Limited proteolysis assays performed with the wild-type and mutant AR receptors incubated with the synthetic agonist R1881 revealed that the P817A mutation resulted in a reduced stabilization of the AR active conformation. Structural analyses showed that this mutation is likely to perturb the beta-sheet interaction between residues 815-817 and 911-913. This structural alteration destabilizes the position of the C-terminal extension, which contains residues critical for androgen function.