Gabriela Romalo

Oestrogen formation from androstenedione in human bone

BACKGROUND AND OBJECTIVE Peripheral aromatization of testosterone and androstenedione Is the principal source for circulating oestrogens In men and In castrated and post‐menopausal women. Since human bone is a target organ for androgens and oestrogens, aromatase activity was assessed In human sponglosa obtained from patients who were undergoing orthopaedic surgery.

Clinical and biochemical investigations and molecular analysis of subjects with mutations in the androgen receptor gene

OBJECTIVE Androgen insensitivity syndromes (AIS) in subjects with 46,XY karyotype and normal or even elevated androgen blood levels are characterized by various aberrations in male differentiation and virilization. AIS is often accompanied by a broad spectrum of abnormal binding characteristics of the androgen receptor (AR). In order to investigate the correlation between the degree of virilization defect and the type of androgen binding abnormalities and/or the nature of the mutation in the AR gene, we determined androgen binding characteristics of the AR protein and the sequence of the AR gene in clinically and biochemically well characterized patients with various degrees of androgen resistance.

Juvenile nasopharyngeal fibroma : Androgen receptors and their significance for tumor growth

Since the publications of Martin, et al. (1948) and Schiff (1959), who were the first to report on the administration of sex hormones to juvenile nasopharyngeal fibroma (JNF) patients, several authors have described the different clinical effects and histologic changes after androgen and estrogen application. Since the mechanism of action of sex steroids in juvenile nasopharyngeal fibroma is almost unknown, the authors have studied androgen receptor binding in cultured tumor fibroblasts from three patients with JNF. Maximum androgen binding (Bmax) of the tumor fibroblasts approximated to that of genital skin fibroblasts, which served as a control androgen target tissue with high receptor density. Furthermore, in vitro experiments showed that the growth rate of tumor fibroblasts increased when testosterone was added to the culture medium, while the addition of two antiandrogens, cyproterone and flutamide, caused a reduction in growth rate.

An androgen receptor mutation in the direct vicinity of the proposed C-terminal α-helix of the ligand binding domain containing the AF-2 transcriptional activating function core is associated with complete androgen insensitivity

Subjects with androgen insensitivity syndromes (AIS) are characterized by a 46, XY karyotype, presence of testes, normal or elevated androgen levels in blood, and impairment of the usual response to androgens associated with various aberrations of male differentiation and virilization ranging from slightly undervirilized men to phenotypic females. Here we describe a novel proline to serine mutation in codon 892 (exon 8) of the androgen receptor in a patient with complete androgen insensitivity. The mutation is located in the direct vicinity of the proposed C-terminal alpha-helix of the ligand binding domain containing the AF-2 transcriptional activating function core. Investigation of androgen binding in cultured testicular fibroblasts of the patient revealed a reduced AR binding capacity (11 fmol/mg protein) and a highly elevated Kd value (3.1 nM) in comparison to control genital skin fibroblasts. Cotransfection studies with an androgen-responsive reporter gene revealed a diminished transactivation property of the mutant androgen receptor.

Oestrogen formation in genital and non-genital skin fibroblasts cultured from patients with hypospadias

OBJECTIVE Hypospadias is the most common birth defect in males. in most cases the aetiology is unknown. Since penile development is androgen dependent and oestrogen can modify androgen action, we compared the formation of oestrogen In penile tissue from patients with hypospadias to those with normal penile development.

Genital Skin Fibroblasts (GF) of Patients with Androgen Insensitivity Syndrome Express Higher Insulin-Like Growth Factor Binding Protein (IGFBP)-2, -3 and -5 than GF of Normally Virilized Males

Background: We investigated the effects of androgens, estradiol (E2) and insulin-like growth factor (IGF)-I on IGF-II, insulin-like growth factor binding protein (IGFBP)-2, -3 and -5 and mRNA in genital fibroblasts (GF) from patients with complete androgen insensitivity (CAIS) and normally virilized males (C). Methods: Proteins were measured by specific RIA and Western ligand blot, and specific mRNA levels by RT-PCR normalized by GAPDH levels. Results: Secretion of IGF-II was lowered in CAIS (p < 0.001) GF and by testosterone + IGF-I in C GF. Secretion of IGFBP-2 was higher (p < 0.001) in CAIS GF and IGFBP-2 mRNA levels were increased by E2 in C GF (p < 0.05). E2 stimulated IGFBP-2, -3 and -5 expression in CAIS GF. CAIS GF also secreted more IGFBP-3 (p < 0.001) and accumulated 3–5 times more IGFBP-5 mRNA than C GF (p < 0.001). Conclusion: In contrast to C GF, the availability of IGF-II in CAIS GF is apparently decreased by two facts: by the decreased expression and by increased expression of IGFBP-2, -3 and -5. Furthermore, E2 and IGF-I modulate the expression of IGF-II and IGFBP in GF. This may play a role in the failure to develop male external genitals in CAIS patients.

Syndromes caused by androgen resistance

Androgen resistance in genetically normal men results when pituitary gonadotropin and testicular testosterone secretion are normal but the physiological androgen response in an androgen target organ is either absent or diminished (Griffin and Wilson 1980; Schweikert 1987). As a result, both the embryonic and postnatal actions of androgens are impaired or absent. It is now recognized that a variety of disorders spanning the spectrum from women with the testicular feminization syndrome to otherwise normal men with either infertility or hypospadias are caused by androgen resistance.

OESTROGEN FORMATION FROM ANDROSTENEDIONE IN HUMAN BONE

BACKGROUND AND OBJECTIVE Peripheral aromatization of testosterone and androstenedione is the principal source for circulating oestrogens in men and in castrated and post-menopausal women. Since human bone is a target organ for androgens and oestrogens, aromatase activity was assessed in human spongiosa obtained from patients who were undergoing orthopaedic surgery. DESIGN AND PATIENTS In initial experiments for assessing aromatization, oestrogen formation from 1,2,6,7-3H-androstenedione was compared with the release of tritiated water from 1 beta-3H-androstenedione. Since the rates of enzyme activity were similar with the two methods, rates of oestrogen formation were determined under standardized conditions with the tritiated water generation technique in bone specimens obtained from 4 men and 11 post-menopausal women. RESULTS The apparent Km of the aromatase ranged between 6 and 50 nM (20.4 +/- 3.9; mean +/- SEM), values in the range of those reported for human placental microsomes. The maximum velocity (Vmax) of the aromatase activity ranged between 0.14 and 1.23 nmol/g DNA/h. CONCLUSIONS Oestrogens formed in human bone may play a physiological role in steroid hormone action in this tissue.