Aromatase

About: Aromatase is a research topic. Over the lifetime, 8083 publications have been published within this topic receiving 316910 citations. The topic is also known as: estrogen synthase & microsomal monooxygenase.

Mechanisms of Estrogen Action

Abstract: Our appreciation of the physiological functions of estrogens and the mechanisms through which estrogens bring about these functions has changed during the past decade. Just as transgenic mice were produced in which estrogen receptors had been inactivated and we thought that we were about to understand the role of estrogen receptors in physiology and pathology, it was found that there was not one but two distinct and functional estrogen receptors, now called ERα and ERβ. Transgenic mice in which each of the receptors or both the receptors are inactive have revealed a much broader role for estrogens in the body than was previously thought. This decade also saw the description of a male patient who had no functional ERα and whose continued bone growth clearly revealed an important function of estrogen in men. The importance of estrogen in both males and females was also demonstrated in the laboratory in transgenic mice in which the aromatase gene was inactivated. Finally, crystal structures of the estrogen r...

Aromatase Cytochrome P450, The Enzyme Responsible for Estrogen Biosynthesis*

Abstract: THE biosynthesis of estrogens appears to occur throughout the entire vertebrate phylum including mammals, birds, reptiles, amphibians, teleost and elasmobranch fish, and Agnatha (hagfish and lampreys) (1–3). It has also been described in the protochordate Amphioxus (4). To our knowledge, estrogen biosynthesis has not been reported in nonvertebrate animal phyla. In most vertebrate species that have been examined, aromatase expression occurs in the gonads and in the brain. This is true of the fish and avian species that have been examined as well as most mammals such as rodents. In many species estrogen biosynthesis in the brain has been implicated in sex-related behavior such as mating responses, and frequently a marked sexually dimorphic difference has been demonstrated. This is true, for example, in avian species in which the song of the male is important in courtship behavior (5). In the case of humans and a number of higher primates, there is a more extensive tissue distribution of estrogen biosynthesi...

Aromatase deficiency in male and female siblings caused by a novel mutation and the physiological role of estrogens

Abstract: The aromatase enzyme complex catalyzes the conversion of androgens to estrogens in a wide variety of tissues, including the ovary, testis, placenta, brain, and adipose tissue. Only a single human gene encoding aromatase P450 (CYP19) has been isolated; tissue-specific regulation is controlled in part by alternative promoters in a tissue-specific manner. We report a novel mutation in the CYP19 gene in a sister and brother. The 28-yr-old XX proband, followed since infancy, exhibited the cardinal features of the aromatase deficiency syndrome as recently defined. She had nonadrenal female pseudohermaphrodism at birth and underwent repair of the external genitalia, including a clitorectomy. At the age of puberty, she developed progressive signs of virilization, pubertal failure with no signs of estrogen action, hypergonadotropic hypogonadism, polycystic ovaries on pelvic sonography, and tall stature. The basal concentrations of plasma testosterone, androstenedione, and 17-hydroxyprogesterone were elevated, wher...

Letrozole Is More Effective Neoadjuvant Endocrine Therapy Than Tamoxifen for ErbB-1– and/or ErbB-2–Positive, Estrogen Receptor–Positive Primary Breast Cancer: Evidence From a Phase III Randomized Trial

Abstract: PURPOSE: Expression of ErbB-1 and ErbB-2 (epidermal growth factor receptor and HER2/neu) in breast cancer may cause tamoxifen resistance, but not all studies concur. Additionally, the relationship between ErbB-1 and ErbB-2 expression and response to selective aromatase inhibitors is unknown. A neoadjuvant study for primary breast cancer that randomized treatment between letrozole and tamoxifen provided a context within which these issues could be addressed prospectively. PATIENTS AND METHODS: Postmenopausal patients with estrogen– and/or progesterone receptor–positive (ER+ and/or PgR+) primary breast cancer ineligible for breast-conserving surgery were randomly assigned to 4 months of neoadjuvant letrozole 2.5 mg daily or tamoxifen 20 mg daily in a double-blinded study. Immunohistochemistry (IHC) for ER and PgR was conducted on pretreatment biopsies and assessed by the Allred score. ErbB-1 and ErbB-2 IHC were assessed by intensity and completeness of membranous staining according to published criteria. RE...

Biological actions of androgens

Abstract: Though unnecessary for life itself, androgens are essential for the propagation of the species and for establishment and maintenance of the quality of life of males through their support of sexual behavior and function, muscle strength, and sense of well-being. In carrying out its many functions, T acts both as hormone and prohormone. It is an outstanding example of the diverse evolutionary utilization of a primitive informational molecule both among and within species. Not only does T act through the androgen receptor both unchanged and via 5 alpha-reduction, but it acts in tissues with a high aromatase level as an estrogen via the estrogen receptor. Furthermore, DHT, binding to the estrogen receptor, can act as an inhibitor of estrogen action. The products of androgen metabolism may also play active regulatory roles in hematopoiesis and in the regulation of certain hepatic enzymes. Table 3 summarizes the actions of secreted T in males indicating the probable effector hormone. While gross hypogonadism is uncommon, mild androgen insufficiency may be much more frequent, especially in older men, and in those receiving treatment for chronic medical conditions. It is quite possible that such individuals would benefit from appropriate androgen therapy were it available, but the current forms of replacement therapy are not very satisfactory. Better approaches are required. With the exception of a small number of secreted proteins, the products of transcription induced by androgens are not, as yet, known. When the androgen receptor gene is cloned it will be possible to identify androgen-regulated genes and their products. It will then be possible to design agents selectively producing specific desired androgenic effects.