Pharmacokinetics and pharmacodynamics of anastrozole in pubertal boys with recent-onset gynecomastia

Testosterone replacement therapy: clinical considerations

INTRODUCTION

As an increasingly popular therapeutic option, testosterone replacement therapy (TRT) has gained significant notoriety for its health benefits in indicated populations, such as those suffering from hypogonadism.

AREAS COVERED

Benefits such as improved libido, muscle mass, cognition, and quality of life have led to widened public interest in testosterone as a health supplement. No therapy exists without side effects; testosterone replacement therapy has been associated with side effects such as an increased risk of polycythemia, benign prostate hypertrophy (BPH), prostate cancer, gynecomastia, testicular atrophy, and infertility. Testosterone replacement therapy is often accompanied by several prophylactic co-therapies aimed at reducing the prevalence of these side effects. Literature searches for sections on the clinical benefits and risks associated with TRT were performed to include clinical trials, meta-analyses, and systematic reviews from the last 10 years.

EXPERT OPINION

Data from clinical studies over the last decade suggest that the benefits of this therapy outweigh the risks and result in overall increased quality of life and remission of symptoms related to hypogonadism. With this in mind, the authors of this review suggest that carefully designed clinical trials are warranted for the investigation of TRT in symptomatic age-related hypogonadism.

Management of Growth Disorders in Puberty: GH, GnRHa, and Aromatase Inhibitors: A Clinical Review

Pubertal children with significant growth retardation represent a considerable therapeutic challenge. In growth hormone (GH) deficiency, and in those without identifiable pathologies (idiopathic short stature), the impact of using GH is significantly hindered by the relentless tempo of bone age acceleration caused by sex steroids, limiting time available for growth. Estrogen principally modulates epiphyseal fusion in females and males. GH production rates and growth velocity more than double during puberty, and high-dose GH use has shown dose-dependent increases in linear growth, but also can raise insulin-like growth factor I concentrations supraphysiologically, and increase treatment costs. Gonadotropin-releasing hormone analogs (GnRHas) suppress physiologic puberty, and when used in combination with GH can meaningfully increase height potential in males and females while rendering adolescents temporarily hypogonadal at a critical time in development. Aromatase inhibitors (AIs) block androgen to estrogen conversion, slowing down growth plate fusion, while allowing normal virilization in males and stimulating longitudinal bone growth via androgen receptor effects on the growth plate. Here, we review the physiology of pubertal growth, estrogen and androgen action on the epiphyses, and the therapeutic impact of GH, alone and in combination with GnRHa and with AIs. The pharmacology of potent oral AIs, and pivotal work on their efficacy and safety in children is also reviewed. Time-limited use of AIs is a viable alternative to promote growth in pubertal males, particularly combined with GH. Use of targeted growth-promoting therapies in adolescence must consider the impact of sex steroids on growth plate fusion, and treatment should be individualized.

Gynecomastia: A systematic review of pharmacological treatments

BACKGROUND

Pubertal gynecomastia (PG), a benign condition with varied reported prevalence, typically appears at 13-14 years-old and is mostly idiopathic and self-limited. Psychologic impairments are common among adolescents with gynecomastia. Surgical intervention is reserved to severe cases and is offered towards the end of puberty. Pharmacological treatment is seldom given by clinicians mainly due to insufficient published data. We conducted this systematic literature review to assess the efficacy, safety, side effects, and complications of pharmacological treatments published.

METHODS

MEDLINE, Embase, and Cochrane CENTRAL were searched for the terms "gynecomastia", "pubertal", and "adolescent" in conjunction with medications from the Selective Estrogen Receptor Modulator (SERM), aromatase inhibitors (AI), and androgens groups in different combinations to optimize the search results. Exclusion criteria included: studies based on expert opinion, similar evidence-based medicine levels studies, and studies which discuss gynecomastia in adults. Selected articles were assessed by two authors. Data collected included: the level of evidence, population size, treatment regimen, follow-up, outcomes, complications, and side effects.

RESULTS

Of 1,425 published studies found and examined meticulously by the authors, only 24 publications met all the study research goals. These were divided into 16 publications of patients treated with SERM, of whom four had AI and four androgens. In general, the data regarding pharmacologic therapy for PG is partial, with insufficient evidence-based research. Tamoxifen and SERM drugs have long been used as treatments for PG. Tamoxifen was the chosen drug of treatment in most of the reviewed studies and found to be effective, safe, and with minimal side effects.

CONCLUSIONS

Pharmacological treatment as a new standard of care has an advantage in relieving behavioral and psychological distress. Although high quality publications are lacking, pharmacological intervention with tamoxifen is appropriate in select patients. Conduction large-scale high-quality studies are warranted with various drugs.

Treatment of Short Stature with Aromatase Inhibitors: A Systematic Review and Meta-Analysis

The objective of the study is to determine the risks and benefits of treating idiopathic short stature (ISS) with aromatase inhibitors (AIs). We comprehensively searched PubMed, Embase, and the China National Knowledge Infrastructure between establishment year and January 31, 2020. Mean difference (MD)/Standardized mean differences (SMD) with 95% confidence intervals (CI) of individual studies were pooled using fixed or random effects models. Subgroup and sensitivity analyses were also performed. Publication bias was estimated using funnel plots and Egger tests. Fourteen studies including 388 participants were included. The meta-analysis results showed that AIs significantly increased final height (MD=2.46, 95% CI: 0.8-4.12) and predicted adult height (MD=0.34, 95% CI: 0.11-0.57). Changes in bone age (MD=-0.1, 95% CI: -0.86-0.66) and bone mineral density (MD=-0.05, 95% CI: -0.19-0.1) were not different between intervention and control group. AI significantly increased testosterone level (SMD=2.01, 95% CI: 0.8-3.23) and reduced estradiol level (SMD=-1.13, 95% CI: -1.87 to -0.40); The intervention and control group had no significant differences in the levels of high-density lipoprotein-cholesterol (SMD=-0.31, 95%CI: -0.68-0.06) and IGF-1 (SMD=0.7, 95% CI: -0.66-2.06) levels. Adverse events were more frequent in the intervention group than in the control group (odds ratio=3.12, 95% CI: 1.44-6.73). In conclusion, both AI monotherapy and AI combination therapy can increase predicted adult height and testosterone levels.

Bioequivalence of Oral Formulations of Anastrozole in Healthy Chinese Male Volunteers: A Randomized, Single-Dose, Two-Period, Two-Sequence Crossover Study

Anastrozole is currently used as first-line treatment in locally advanced or metastatic breast cancer. A generic anastrozole tablet was developed to offer an alternative to the marketed tablet formulation. The aim of the current study was to evaluate the bioequivalence between the test and reference formulations of anastrozole in a single-dose, 2-period, 2-sequence crossover study with a 14-day washout interval. A total of 20 healthy male Chinese volunteers were enrolled and completed the study, after oral administration of a single dose of 1.0-mg test and reference formulations of anastrozole. The blood samples were collected at different times and were determined by a fully validated high-pressure liquid chromatography-tandem mass spectrometry method. The evaluated pharmacokinetic parameters, including C_max , AUC_0-t , and AUC_0-∞ , were assessed for bioequivalence based on current guidelines. The observed pharmacokinetic parameters of anastrozole of the test drug were similar to those of the reference formulation. The 90% confidence intervals of test/reference ratios for C_max , AUC_0-t , and AUC_0-∞ were within the bioequivalence acceptance range of 80%-125%. The results obtained from these healthy Chinese subjects in this study suggest that the test formulation of anastrozole 1.0-mg tablet is bioequivalent to the reference formulation (Arimidex 1.0-mg tablet).

The use of aromatase inhibitors in boys with short stature: what to know before prescribing?

Aromatase is a cytochrome P450 enzyme (CYP19A1 isoform) able to catalyze the conversion of androgens to estrogens. The aromatase gene mutations highlighted the action of estrogen as one of the main regulators of bone maturation and closure of bone plate. The use of aromatase inhibitors (AI) in boys with short stature has showed its capability to improve the predicted final height. Anastrozole (ANZ) and letrozole (LTZ) are nonsteroidal inhibitors able to bind reversibly to the heme group of cytochrome P450. In this review, we describe the pharmacokinetic profile of both drugs, discussing possible drug interactions between ANZ and LTZ with other drugs. AIs are triazolic compounds that can induce or suppress cytochrome P450 enzymes, interfering with metabolism of other compounds. Hydroxilation, N-dealkylation and glucoronidation are involved in the metabolism of AIs. Drug interactions can occur with azole antifungals, such as ketoconazole, by inhibiting CYP3A4 and by reducing the clearance of AIs. Antiepileptic drugs (lamotrigine, phenobarbital, and phenytoin) also inhibit aromatase. Concomitant use of phenobarbital or valproate has a synergistic effect on aromatase inhibition. Therefore, it is important to understand the pharmacokinetics of AIs, recognizing and avoiding possible drug interactions and offering a safer prescription profile of this class of aromatase inhibitors. Arch Endocrinol Metab. 2017;61(3):391-7.

Randomized Trial of Aromatase Inhibitors, Growth Hormone, or Combination in Pubertal Boys with Idiopathic, Short Stature

CONTEXT

Growth of short children in puberty is limited by the effect of estrogen on epiphyseal fusion.

OBJECTIVES

To compare: 1) the efficacy and safety of aromatase inhibitors (AIs) vs GH vs AI/GH on increasing adult height potential in pubertal boys with severe idiopathic short stature (ISS); and 2) differences in body composition among groups.

DESIGN

Randomized three-arm open-label comparator.

SETTING

Outpatient clinical research.

PATIENTS

Seventy-six pubertal boys [mean (SE) age, 14.1 (0.1) years] with ISS [height SD score (SDS), -2.3 (0.0)].

INTERVENTION

Daily AIs (anastrozole or letrozole), GH, or AI/GH for 24-36 months.

OUTCOMES

Anthropometry, bone ages, dual x-ray absorptiometry, spine x-rays, hormones, safety labs.

RESULTS

Height gain [mean (SE)] at 24 months was: AI, +14.0 (0.8) cm; GH, +17.1 (0.9) cm; AI/GH, +18.9 (0.8) cm (P < .0006, analysis of covariance). Height SDS was: AI, -1.73 (0.12); GH, -1.43 (0.14); AI/GH, -1.25 (0.12) (P < .0012). Those treated through 36 months grew more. Regardless of treatment duration, height SDS at near-final height [n = 71; age, 17.4 (0.2) years; bone age, 15.3 (0.1) years; height achieved, ∼97.6%] was: AI, -1.4 (0.1); GH, -1.4 (0.2); AI/GH, -1.0 (0.1) (P = .06). Absolute height change was: AI, +18.2 (1.6) cm; GH, +20.6 (1.5) cm; AI/GH, +22.5 (1.4) cm (P = .01) (expected height gain at -2.0 height SDS, +13.0 cm). AI/GH had higher fat free mass accrual. Measures of bone health, safety labs, and adverse events were similar in all groups. Letrozole caused higher T and lower estradiol than anastrozole.

CONCLUSIONS

Combination therapy with AI/GH increases height potential in pubertal boys with ISS more than GH and AI alone treated for 24-36 months with a strong safety profile.

Aromatase inhibitors for short stature in male children and adolescents

BACKGROUND

As a result of the essential role of oestrogens in epiphyseal closure, aromatase inhibitors have been trialled as an intervention to improve height outcomes in male children and adolescents by inhibiting the conversion of testosterone to oestradiol.

OBJECTIVES

To assess the effects of aromatase inhibitors in male children and adolescents with short stature.

SEARCH METHODS

To identify relevant trials, we searched the Cochrane Library (2014, Issue 7), MEDLINE, EMBASE, and the World Health Organization (WHO) ICTRP trial register from their inception until August 2014. In addition, we conducted citation searches and screened reference lists of included trials.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) if they compared use of an aromatase inhibitor with placebo in male children and adolescents with short stature.

DATA COLLECTION AND ANALYSIS

Two authors independently screened titles and abstracts for relevance. Both authors carried out screening for inclusion, data extraction, and risk of bias assessment, with any disagreements resolved following discussion. We assessed trials for quality of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) instrument. We contacted study authors regarding missing information. Primary outcomes were final or near-final height, adverse events, and health-related quality of life. Secondary outcomes included all-cause mortality, cognitive outcomes, socioeconomic effects, laboratory measures, short-term growth parameters, and assessment of effects on bone health. Meta-analysis was not appropriate due to the substantial clinical heterogeneity between trials; we presented the findings of the review in narrative format.

MAIN RESULTS

We included four RCTs involving 207 participants (84 on interventions) in the review. Trials included males with constitutional delay of growth and puberty (CDGP), idiopathic short stature (ISS), and growth hormone (GH) deficiency. Three of the trials had an overall low or unclear risk of bias for primary outcomes. Short-term growth outcomes, such as predicted adult height, improved in all trials. Just one trial reported the primary outcome of final and near-final height as an extension under non-randomised conditions. None of the trials assessed health-related quality of life. One publication provided detailed information regarding the incidence of adverse events. A significant proportion (45%) of prepubertal boys with ISS treated with letrozole developed mild morphological abnormalities of their vertebrae, compared with none in the placebo group.

AUTHORS' CONCLUSIONS

Available evidence suggested that aromatase inhibitors improved short-term growth outcomes. There was no evidence to support an increase in final adult height, based on limited data, with only one of four trials publishing final height data under non-randomised conditions.

Surgical treatment of primary gynecomastia in children and adolescents

PURPOSE

Idiopathic gynecomastia is a common diagnosis in children and adolescents. Though medical treatments reveal potentially harmful side effects, surgical interventions are performable in numerous techniques. In children and adolescents, only minimal evidence exists. This retrospective study presents our experiences with two common surgical techniques, namely subcutaneous mastectomy and combination with liposuction.

PATIENTS AND METHODS

This retrospective study included all patients <18 years who underwent surgery due to idiopathic gynecomastia. Height, weight and grade of gynecomastia according to Simon's classification before surgery were reviewed in all patients' files. Additionally, duration of surgery, inpatient stay and postoperative complications were documented. Follow-up examinations were performed with assessment of scar formation, numbness and retraction of the nipple region. Furthermore, patients were asked to report on general satisfaction with surgery (satisfactory/not satisfactory) and esthetic outcome on a numeric scale (1 = good, 6 = bad).

RESULTS

37 patients underwent surgery for verified idiopathic gynecomastia. Grade of gynecomastia was I° in 13.5% (n = 5), II° in 40.5% (n = 15) and III° in 46% (n = 17) of cases. Subcutaneous mastectomy was applied in 11 patients (group I, 30%) and both subcutaneous mastectomy and liposuction in 26 patients (group II, 70.3%). Postoperative complications occurred in two patients. Long-term follow-up was performed in 32 patients after a median of 34 months (range 6-96 months). Hypertrophic scar formation was seen in one patient (3%) and nipple retraction in two patients (5%). Recurrence of gynecomastia occurred in two patients (5%). Patient rating was satisfactory in 9% of cases and esthetic outcome was received with a median of 2.0 (1-5). In comparing both surgical techniques, combination of mastectomy and liposuction revealed better results in every measure except for surgical duration (median 73 vs. 90 min).

CONCLUSION

Surgical correction of gynecomastia remains a purely elective intervention. In contrast to adults, skin in children and adolescents provides high retractability. Therefore, open reduction combined with minimally invasive liposuction was proven useful.

Gynecomastia: physiopathology, evaluation and treatment

Gynecomastia (GM) is characterized by enlargement of the male breast, caused by glandular proliferation and fat deposition. GM is common and occurs in adolescents, adults and in old age. The aim of this review is to discuss the pathophysiology, etiology, evaluation and therapy of GM. A hormonal imbalance between estrogens and androgens is the key hallmark of GM generation. The etiology of GM is attributable to physiological factors, endocrine tumors or dysfunctions, non-endocrine diseases, drug use or idiopathic causes. Clinical evaluation must address diagnostic confirmation, search for an etiological factor and classify GM into severity grades to guide the treatment. A proposal for tailored therapy is presented. Weight loss, reassurance, pharmacotherapy with tamoxifen and surgical correction are the therapeutic options. For long-standing GM, the best results are generally achieved through surgery, combining liposuction and mammary adenectomy.

Aromatase inhibitors in pediatrics

Aromatase, an enzyme located in the endoplasmic reticulum of estrogen-producing cells, catalyzes the rate-limiting step in the conversion of androgens to estrogens in many tissues. The clinical features of patients with defects in CYP19A1, the gene encoding aromatase, have revealed a major role for this enzyme in epiphyseal plate closure, which has promoted interest in the use of inhibitors of aromatase to improve adult height. The availability of the selective aromatase inhibitors letrozole and anastrozole--currently approved as adjuvant therapy for breast cancer--have stimulated off-label use of aromatase inhibitors in pediatrics for the following conditions: hyperestrogenism, such as aromatase excess syndrome, Peutz-Jeghers syndrome, McCune-Albright syndrome and functional follicular ovarian cysts; hyperandrogenism, for example, testotoxicosis (also known as familial male-limited precocious puberty) and congenital adrenal hyperplasia; pubertal gynecomastia; and short stature and/or pubertal delay in boys. Current data suggest that aromatase inhibitors are probably effective in the treatment of patients with aromatase excess syndrome or testotoxicosis, partially effective in Peutz-Jeghers and McCune-Albright syndrome, but probably ineffective in gynecomastia. Insufficient data are available in patients with congenital adrenal hyperplasia or functional ovarian cysts. Although aromatase inhibitors appear effective in increasing adult height of boys with short stature and/or pubertal delay, safety concerns, including vertebral deformities, a decrease in serum HDL cholesterol levels and increase of erythrocytosis, are reasons for caution.

Gynecomastia: incidence, causes and treatment

Gynecomastia is a benign proliferation of glandular tissue of the breast in males. It is common during three phases in the age distribution curve: the neonatal period, puberty and senescence. An imbalance between estrogen and androgen action at the level of breast tissue is believed to be the underlying pathophysiology. Initial steps in the clinical evaluation involve differentiating it from pseudogynecomastia and ruling out male breast carcinoma. A selective laboratory and radiological work-up should follow to identify the underlying cause. Pubertal gynecomastia resolves spontaneously in the majority of adolescents, and hence reassurance and observation is regarded as the best approach. In adults with persistent painful gynecomastia, a short-term trial of medical therapy is an option that has shown good results. For chronic, bothersome gynecomastia, removal by plastic surgery is the treatment of choice.

Bicalutamide plus anastrozole for the treatment of gonadotropin-independent precocious puberty in boys with testotoxicosis: a phase II, open-label pilot study (BATT)

OBJECTIVE

To evaluate the efficacy, tolerability, and pharmacokinetics of bicalutamide plus anastrozole in young males with testotoxicosis.

METHODS

This was a multicenter, open-label, single-arm, 12-month, Phase II pilot trial in 14 males (2-9 years) with testotoxicosis treated with bicalutamide (12.5, 25, 50, or 100 mg) and anastrozole (0.5 or 1 mg) daily. The primary outcome was change in growth rate.

RESULTS

At 1 year, the mean (standard deviation) change from baseline in growth rate was -1.6 (+/- 5.1) cm/year and -0.1 (+/- 1.8) SD units, and in bone maturation was -2.3 (+/- 0.5) years. The bone age/chronological age ratio was reduced from 2.1 (+/- 0.6) at baseline to 1.0 (+/- 0.4) (p = 0.00013). Steady-state trough R-bicalutamide and anastrozole concentrations were attained by Day 21 and 8, respectively. Gynecomastia (42.9%) and breast tenderness (12.5%) were the most common treatment-related adverse events.

CONCLUSIONS

Treatment of testotoxicosis with bicalutamide plus anastrozole resulted in slower growth rate.

Use of aromatase inhibitors in children and adolescents: what's new?

PURPOSE OF REVIEW

Aromatase inhibitors have been reported to increase height prediction in boys with short stature, and in boys and girls with gonadotropin-independent precocious puberty. The following review discusses data published since 2008 regarding the safety and efficacy of aromatase inhibitors in pediatric patients.

RECENT FINDINGS

Third-generation aromatase inhibitors in combination with antiandrogens appear effective in preventing bone age advancement and virilization in boys with familial male-limited precocious puberty (FMPP). Letrozole, but not anastrozole, decreased bleeding episodes and bone age advancement in girls with McCune-Albright syndrome (MAS), despite ovarian enlargement. Letrozole-treated boys with idiopathic short stature (ISS) had no loss of bone density but were noted to have more vertebral abnormalities than a placebo group. Two years of letrozole therapy did not increase predicted adult height in pre and peripubertal boys with ISS when re-assessed 4 years after the treatment period.

SUMMARY

Aromatase inhibitors together with an antiandrogen appear to be a very promising treatment for FMPP. Further longer-term studies with letrozole are needed in MAS. The prevalence of vertebral deformities should be evaluated prospectively in patients treated with aromatase inhibitors. Adult height data are still lacking in pediatric patients treated with aromatase inhibitors. Two years of therapy in pre and peripubertal short boys does not appear to increase adult height. Hemogram, lipids, and bone density should be periodically assessed in treated patients. Further controlled studies are needed to demonstrate safety and efficacy of aromatase inhibitors in pediatric patients.

Treatment of adolescent gynecomastia

PURPOSE

Adolescent gynecomastia is common but variable in severity. The disease may be self-limited. Although antiestrogen therapy can be used in persistent gynecomastia, results are mixed. Subcutaneous mastectomy via a circumareloar incision is familiar to most pediatric surgeons and provides excellent cosmetic results in most cases. Severe gynecomastia may require alternative procedures. There is little information in the pediatric surgical literature to provide the pediatric surgeon with treatment options for these children. A variety of techniques have been used by plastic surgeons for female patients requiring breast reduction and are sometimes a useful addition to the surgical repertoire for the management of very large breasts in adolescent gynecomastia. We reviewed our experience with the use of inferior pedicle reduction mammaplasty and subcutaneous mastectomy in adolescents with gynecomastia and describe the techniques used.

METHODS

After obtaining institutional review board approval, a retrospective review was conducted on all patients operated on for gynecomastia from January 1999 to March 2009. Data recorded included patient demographics, diagnostic evaluation, medical and surgical treatment, complications, and outcome.

RESULTS

Twenty patients underwent an operation for gynecomastia. Eight patients had bilateral inferior pedicle reduction mammaplasty, and 12 patients underwent either unilateral or bilateral subcutaneous mastectomy. The mean age at operation was 15.5 years (range, 14-18 years). In all cases, the histopathologic feature was consistent with gynecomastia. There were no postoperative wound infections. One patient developed a seroma after subcutaneous mastectomy requiring drainage. The mean amount of tissue removed after bilateral reduction mammaplasty was 275.1 g. No patients had devascularization of the nipple-areolar complex or nipple loss. One patient had mild subcutaneous asymmetry after a reduction mammaplasty that required no further intervention. Seven patients (87%) had an excellent cosmetic outcome after reduction mammaplasty. Mean length of follow-up was 18.8 months.

CONCLUSIONS

Although many adolescents with true gynecomastia have mild or self-limited disease, operative treatment may provide significant benefit to the remainder. Milder grades of gynecomastia can be managed with subcutaneous mastectomy. Selected severe cases can be safely and effectively treated with reduction mammaplasty.