Aromatase is the enzyme that catalyzes the conversion of androgens to estrogens. Initial studies of its enzymatic activity and function took place in an environment focused on estrogen as a component of the birth control pill. At an early stage, investigators recognized that inhibition of this enzyme could have major practical applications for treatment of hormone-dependent breast cancer, alterations of ovarian and endometrial function, and treatment of benign disorders such as gynecomastia. Two general approaches ultimately led to the development of potent and selective aromatase inhibitors. One targeted the enzyme using analogs of natural steroidal substrates to work out the relationships between structure and function. The other approach initially sought to block adrenal function as a treatment for breast cancer but led to the serendipitous finding that a nonsteroidal P450 steroidogenesis inhibitor, aminoglutethimide, served as a potent but nonselective aromatase inhibitor. Proof of the therapeutic concept of aromatase inhibition involved a variety of studies with aminoglutethimide and the selective steroidal inhibitor, formestane. The requirement for even more potent and selective inhibitors led to intensive molecular studies to identify the structure of aromatase, to development of high-sensitivity estrogen assays, and to "mega" clinical trials of the third-generation aromatase inhibitors, letrozole, anastrozole, and exemestane, which are now in clinical use in breast cancer. During these studies, unexpected findings led investigators to appreciate the important role of estrogens in males as well as in females and in multiple organs, particularly the bone and brain. These studies identified the important regulatory properties of aromatase acting in an autocrine, paracrine, intracrine, neurocrine, and juxtacrine fashion and the organ-specific enhancers and promoters controlling its transcription. The saga of these studies of aromatase and the ultimate utilization of inhibitors as highly effective treatments of breast cancer and for use in reproductive disorders serves as the basis for this first Endocrine Reviews history manuscript.

History of Aromatase: Saga of an Important Biological Mediator and Therapeutic Target

Clinical practice. Gynecomastia.

Gynecomastia, defined as benign proliferation of male breast glandular tissue, is usually caused by increased estrogen activity, decreased testosterone activity, or the use of numerous medications. Although a fairly common presentation in the primary care setting and mostly of benign etiology, it can cause patients considerable anxiety. The initial step is to rule out pseudogynecomastia by careful history taking and physical examination. A stepwise approach that includes imaging and laboratory testing to exclude neoplasms and endocrinopathies may facilitate cost-effective diagnosis. If results of all studies are normal, idiopathic gynecomastia is diagnosed. The evidence in this area is mainly of observational nature and lower quality.

https://www.mayoclinicproceedings.org/article/S0025-6196(11)60671-X/pdf

Gynecomastia: Pathophysiology, Evaluation, and Management

Background: The limitations of serum testosterone and estradiol (E2) measurements using non-extraction platform immunoassays (IAs) are widely recognized. Switching to more specific mass spectrometry (MS)-based methods has been advocated, but directly comparative data on the two methods are scarce. Methods:We compared serumtestosterone and E2measurements in a large sample of middle-aged/elderly men using a common platform IA and a gas chromatography (GC)-MS method, in order to assess their limitations and advantages, and to diagnose male hypogonadism. Of subjects from the European Male Aging Study (n = 3174; age 40-79 years), peripheral serum testosterone and E 2 were analyzed using established commercial platform IAs (Roche Diagnostics E170) and in-house GC-MS methods. Results: Over a broad concentration range, serum testosterone concentration measured by IA and MS showed high correlation (R=0.93, P 40.8 pmol/l). Using MS as the comparator method, IA ascertained low test osterone compatible with hypogonadism ( 120 pmol/l) 88.4 and 88.6%. Conclusion: A validated platform IA is sufficient to detect subnormal testosterone concentrations in the diagnosis of male hypogonadism. The IA used for E 2 measurements showed poor correlation with MS and may only be suitable for the detection of high E 2 in men. © 2012 European Society of Endocrinology.

/pdf/comparison-of-serum-testosterone-and-estradiol-measurements-3xpcwecsd0.pdf

Comparison of serum testosterone and estradiol measurements in 3174 European men using platform immunoassay and mass spectrometry; relevance for the diagnostics in aging men

Background Gynecomastia (GM) is a benign proliferation of the glandular tissue of the breast in men. It is a frequent condition with a reported prevalence of 32-65%, depending on the age and the criteria used for definition. GM of infancy and puberty are common, benign conditions resolving spontaneously in the majority of cases. GM of adulthood is more prevalent among the elderly and proper investigation may reveal an underlying pathology in 45-50% of cases. Objectives The aim was to provide clinical practice guidelines for the evaluation and management of GM. Materials and methods A literature search of articles in English for the term 'gynecomastia' was conducted. Evidence-based recommendations were developed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system. Results A set of five statements and fifteen clinical recommendations was formulated. Conclusions The purpose of GM assessment should be the detection of underlying pathological conditions, reversible causes (administration/abuse of aggravating substances), and the discrimination from other breast lumps, particularly breast cancer. Assessment should comprise a thorough medical history and physical examination of the breast and genitalia (including testicular ultrasound). A set of laboratory investigations may integrate the evaluation: testosterone (T), estradiol (E2), sex hormone-binding globulin (SHBG), luteinizing hormone (LH), follicular stimulating hormone (FSH), thyroid stimulating hormone (TSH), prolactin, human chorionic gonadotropin (hCG), alpha-fetal protein (AFP), liver and renal function tests. Breast imaging may be used whenever the clinical examination is equivocal. In suspicious lesions, core needle biopsy should be sought directly instead. Watchful waiting is recommended after treatment of underlying pathology or discontinuation of substances associated with GM. T treatment should be offered to men with proven T deficiency. The use of selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs) and non-aromatizable androgens is not justified in general. Surgical treatment is the therapy of choice for patients with long-lasting GM. Summary of statements (s) and recommendations (r) S1. Gynecomastia (GM) is a benign proliferation of glandular tissue of the breast in males. S2. GM of infancy is a common condition that usually resolves spontaneously, typically within the first year of life. S3. GM of puberty is a common condition, affecting approximately 50% of mid-pubertal boys; in more than 90% of cases, it resolves spontaneously within 24 months. S4. The prevalence of GM in adulthood increases with increasing age; proper investigation may reveal an underlying pathology in approximately 45-50% of the cases. S5. Male breast cancer is rare; GM should not be considered a premalignant condition. The following recommendations are divided into 'strong', denoted by the number 1 and associated with the terminology 'we recommend', and 'weak' denoted by the number 2 and associated with the phrase 'we suggest'. The grading of the quality of evidence is denoted as follows: ⊕○○○ for very low-quality evidence; ⊕⊕○○ for low quality; ⊕⊕⊕○ for moderate quality; and ⊕⊕⊕⊕ for high quality. R1. The presence of an underlying pathology should be considered in GM of adulthood. We recommend that the identification of an apparent reason for GM in adulthood, including the use of medication known to be associated with GM, should not preclude a detailed investigation (1 ⊕⊕⊕○). R2. We suggest that the initial screening to rule out lipomastia, obvious breast cancer, or testicular cancer might be performed by a general practitioner or another non-specialist (2 ⊕○○○). R3. We recommend that in those cases where a thorough diagnostic workup is warranted, it should be performed by a specialist (1 ⊕○○○). R4. We recommend that the medical history should include information on the onset and duration of GM, sexual development and function, and administration or abuse of substances associated with GM (1 ⊕⊕⊕○). R5. We recommend that the physical examination should detect signs of under-virilization or systemic disease (1 ⊕⊕⊕⊕). R6. We recommend that breast examination should confirm the presence of palpable glandular tissue to discriminate GM from lipomastia (pseudo-gynecomastia) and rule out the suspicion of malignant breast tumor (1 ⊕⊕⊕⊕). R7. We recommend that the physical examination should include the examination of the genitalia to rule out the presence of a palpable testicular tumor and to detect testicular atrophy (1 ⊕⊕⊕⊕). R8. We recommend that genitalia examination is aided by a testicular ultrasound, as the detection of a testicular tumor by palpation has low sensitivity (1 ⊕⊕○○). R9. We suggest that a set of evaluations may include T, E2 , SHBG, LH, FSH, TSH, prolactin, hCG, AFP, and liver and renal function tests (2 ⊕⊕○○). R10. We suggest that breast imaging may offer assistance, where the clinical examination is equivocal (2 ⊕⊕○○). R11. We suggest that, if the clinical picture is suspicious for a malignant lesion, core needle biopsy should be performed (2 ⊕⊕○○). R12. We recommend watchful waiting after treatment of underlying pathology or discontinuation of the administration/abuse of substances associated with GM (1 ⊕⊕○○). R13. We recommend that T treatment should be offered only to men with proven testosterone deficiency (1 ⊕⊕⊕○). R14. We do not recommend the use of selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs), or non-aromatizable androgens in the treatment of GM in general (1 ⊕⊕○○). R15. We suggest surgical treatment only for patients with long-lasting GM, which does not regress spontaneously or following medical therapy. The extent and type of surgery depend on the size of breast enlargement, and the amount of adipose tissue (2 ⊕⊕○○).

https://onlinelibrary.wiley.com/doi/pdf/10.1111/andr.12636

EAA clinical practice guidelines-gynecomastia evaluation and management.

An imbalance between estrogen action relative to androgen action at the breast tissue level results in gynecomastia. Enhancement of aromatization of androgens to estrogens is important in the pathogenesis of gynecomastia associated with obesity, aging, puberty, liver disease, thyrotoxicosis, 17-oxosteroid reductase deficiency. Klinefelter's syndrome, and neoplasms of the testes, adrenals and liver. A primary aromatase excess syndrome with exuberant gynecomastia had been found both sporadically and in a familial setting. Although aromatase inhibition would appear to be an important class of drugs to treat gynecomastia, relatively little published data with these drugs exist and most concern the use of delta1-testolactone, which reduces the size of the breast glandular tissue, but does not completely ameliorate the problem. Studies with the newer generation of more potent aromatase inhibitors need to be carried out.

/pdf/aromatase-and-gynecomastia-v6g407u4ra.pdf

Aromatase and gynecomastia.

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Aromatase and gynecomastia.