Selective modulation of estrogen receptor in obese men with androgen deficiency: A systematic review and meta-analysis.

BACKGROUND: Although selective estrogen receptor modulators have been proposed as a treatment for men with central functional hypogonadism, only a few data have been produced in men with obesity-related functional androgen deficiency. OBJECTIVE: To determine whether and to what extent selective estrogen receptor modulators are an effective and safe therapy in men with obesity-related functional androgen deficiency. MATERIALS AND METHODS: A thorough search of PubMed, Web of Science, Scopus, and Cochrane Library databases was performed to identify studies comparing testosterone levels before and after treatment. Mean differences with 95% coefficient intervals were combined using random effects models. Funnel plot, Egger's test, and trim-and-fill analysis were used to assess publication bias. RESULTS: Seven studies met the inclusion criteria providing information on 292 men with obesity-related functional androgen deficiency treated with clomiphene citrate (12.5-50 mg daily) or enclomiphene citrate (12.5-25 mg daily) for 1.5-4 months. The pooled estimates indicated a significant increase in testosterone levels both with clomiphene (mean difference: 11.56 nmol/L; 95% coefficient interval: 9.68, 13.43; I2  = 69%, pfor heterogeneity  = 0.01) and enclomiphene citrate (mean difference: 7.50 nmol/L; 95% coefficient interval: 6.52, 8.48; I2  = 4%, pfor heterogeneity  = 0.37). After the exclusion of one study on severely obese men, who exhibited the highest response rate to clomiphene citrate, the heterogeneity disappeared (mean difference: 10.27 nmol/L; 95% coefficient interval: 9.39, 11.16; I2  = 0%, pfor heterogeneity  = 0.66). No publication bias was revealed by Egger's test and trim-and-fill analysis. No treatment-related unexpected findings regarding safety profile were registered. DISCUSSION AND CONCLUSION: Treatment with clomiphene citrate and enclomiphene citrate may be an effective and safe alternative to testosterone replacement therapy in men with obesity-related functional androgen deficiency. Further long-term studies are warranted to define clinical reflections of the selective estrogen receptor modulators-induced increase in testosterone levels and to better clarify the safety profile.

Are SERMs safe and effective for the treatment of hypogonadism in men?

YES. For both normal-weight and obese men with low testosterone levels and hypogonadal symptoms, selective estrogen receptor modulators (SERMs), such as clomiphene citrate (CC) and enclomiphene citrate (EC), appear to be effective and safe for improving serum testosterone levels (strength of recommendation [SOR]: C, disease-oriented outcomes from randomized controlled trials [RCTs] and cohort studies). Studies also show that symptom improvement is comparable to that with exogenous testosterone replacement and similar to eugonadal men (SOR: B, patient-oriented outcomes from retrospective cohort studies).

Enclomiphene citrate: A treatment that maintains fertility in men with secondary hypogonadism.

INTRODUCTION: Hypogonadism is an important issue among the male population. Treatments such as exogenous testosterone have become very popular. One of the adverse effects of testosterone is its suppression of fertility. This has lead to the use of alternative therapies such as selective estrogen receptor modulators (SERMs) that aim to correct hypogonadism without reducing fertility. Areas covered: The SERM, clomiphene citrate, which is approved by the FDA for the treatment of ovarian dysfunction, has been shown to have beneficial effects on male hypogonadism. Clomiphene citrate exists as a mixture of both the cis-isomer (zuclomiphene) and the trans-isomer (enclomiphene). The literature has suggested that most of the beneficial effects of clomiphene are due to the trans-isomer enclomiphene. Zuclomiphene contributes little to the intended outcomes. The purpose of this drug profile is to examine the available literature on the trans-isomer enclomiphene. Expert opinion: Enclomiphene has been shown to increase testosterone levels while stimulating FSH and LH production. Initial studies demonstrated that enclomiphene maintains the androgenic benefit of clomiphene citrate without the undesirable effects attributable to zuclomiphene. This article reviews the difficulties associated with the FDA approval of a new molecular entity related to the treatment of hypogonadism.

Serum levels of enclomiphene and zuclomiphene in men with hypogonadism on long-term clomiphene citrate treatment.

OBJECTIVES: To determine the relative concentrations of enclomiphene (ENC) and zuclomiphene (ZUC) isomers in men with hypogonadism on long-term clomiphene citrate (CC) therapy, and to determine whether patient age, body mass index (BMI) or duration of therapy were predictive of relative concentrations of ENC and ZUC. PATIENTS AND METHODS: Men already receiving CC 25 mg daily therapy for secondary hypogonadism for a minimum of 6 weeks were recruited to have their ENC and ZUC levels assessed. Total testosterone, free testosterone, oestradiol, follicle stimulating hormone (FSH), and luteinizing hormone (LH) before initiation of and while on CC therapy were recorded for all patients. Patient demographics including age, BMI and medical comorbidites were recorded. Serum samples were obtained at the time of enrolment to determine ENC and ZUC concentrations. RESULTS: A total of 15 men were enrolled in the period from June 2015 to August 2015. The median (range) patient age was 36 (22-70) years, BMI 32.0 (21.1-40.3) kg/m2 and duration of treatment 25.9 (1.7-86.6) months. Baseline median total testosterone, oestradiol and LH levels were 205.0 ng/dL, 17.0 pg/mL and 4.0 mlU/mL, respectively. The post-treatment median total testosterone, oestradiol and LH level increased to 488.0 ng/dL, 34.0 pg/mL and 6.1 mIU/mL, respectively (all P<0.001). The median ENC and ZUC concentrations were 2.2 and 44.0 ng/mL, respectively. After at least 6 weeks of CC therapy, the median ZUC: ENC serum concentration ratio was 20:1. On linear regression analysis. patient age, BMI, duration of treatment and serum testosterone levels were not predictive of ENC or ZUC concentrations. CONCLUSIONS: Long-term CC therapy resulted in a significant alteration of ENC and ZUC concentrations, with ZUC as the predominant isomer. Given the vastly different biochemical and toxicological properties of ENC and ZUC, this study supports the need for the development of a pure selective oestrogen receptor antagonist for the treatment of men with hypogonadism.

Enclomiphene citrate for the treatment of secondary male hypogonadism.

INTRODUCTION: Hypogonadism is a growing concern in an aging male population. Historically treated using exogenous testosterone, concerns about possible adverse effects of testosterone have led physicians to seek alternative treatment approaches. AREAS COVERED: Enclomiphene citrate is the trans isomer of clomiphene citrate, a non-steroidal estrogen receptor antagonist that is FDA-approved for the treatment of ovarian dysfunction in women. Clomiphene citrate has also been used off-label for many years to treat secondary male hypogonadism, particularly in the setting of male infertility. Here we review the literature examining the efficacy and safety of enclomiphene citrate in the setting of androgen deficiency. EXPERT OPINION: Initial results support the conclusion that enclomiphene citrate increases serum testosterone levels by raising luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels, without negatively impacting semen parameters. The ability to treat testosterone deficiency in men while maintaining fertility supports a role for enclomiphene citrate in the treatment of men in whom testosterone therapy is not a suitable option.

Oral enclomiphene citrate raises testosterone and preserves sperm counts in obese hypogonadal men, unlike topical testosterone: restoration instead of replacement.

OBJECTIVES: To determine the effects of daily oral doses of enclomiphene citrate compared with topical testosterone gel treatment on serum total testosterone (TT), luteinising hormone (LH), follicle-stimulating hormone (FSH), and sperm counts in men with secondary hypogonadism. PATIENTS AND METHODS: Two parallel randomised, double-blind, double-dummy, placebo-controlled, multicentre, phase III studies were undertaken to evaluate two doses of enclomiphene citrate vs testosterone gel (AndroGel(®) 1.62%) on TT, LH, FSH, and sperm counts in overweight men aged 18-60 years with secondary hypogonadism. Men were screened and enrolled in the trials (ZA-304 and ZA-305). All enrolled men had early morning serum TT levels in the low or low normal range (≤300 ng/dL; ≤10.4 nmol/L) and had low or normal LH (<9.4 IU/L) levels measured on two separate occasions 2-10 days apart. Serum samples were obtained over the course of the study to determine relevant hormone levels at baseline and after 16 weeks of treatment. Men provided semen samples twice to enroll at the beginning and twice at the end of the study. RESULTS: TT levels increased between baseline and after 16 weeks of treatment in all the treatment groups. FSH and LH levels increased in the enclomiphene citrate groups and decreased in the testosterone gel group at 16 weeks. Enclomiphene citrate maintained sperm concentration in the normal range over the treatment period, while there was a marked reduction in spermatogenesis in the testosterone gel group. CONCLUSIONS: Enclomiphene citrate consistently increased serum TT, LH and FSH, restoring normal levels of serum TT. Enclomiphene citrate treatment maintained sperm concentrations in the normal range. The effects on TT were also seen with testosterone replacement via testosterone gel but sperm counts were not maintained.

Enclomiphene citrate stimulates testosterone production while preventing oligospermia: a randomized phase II clinical trial comparing topical testosterone.

OBJECTIVE: To determine the effect of enclomiphene citrate in men with secondary hypogonadism. DESIGN: Phase II clinical trial. SETTING: Community dwelling men making visits to physician offices. PATIENT(S): Men with secondary hypogonadism. INTERVENTION(S): Oral administration of enclomiphene citrate or 1% topical T gel. MAIN OUTCOME MEASURE(S): Luteinizing hormone, FSH, T, and semen analysis. RESULT(S): Treatment with enclomiphene citrate resulted in increased morning serum T, E2, and LH levels similar to those obtained with a topical T gel in men with secondary hypogonadism. Follicle-stimulating hormone and LH were increased with enclomiphene, and sperm counts were conserved. CONCLUSION(S): Enclomiphene citrate reverses the two hallmarks of secondary hypogonadism, namely, low serum total T and low or inappropriately normal LH while preserving sperm production. CLINICAL TRIAL REGISTRATION NUMBER: NCT01270841 (ClinicalTrials.gov Identifier NCT01270841).

Oral enclomiphene citrate stimulates the endogenous production of testosterone and sperm counts in men with low testosterone: comparison with testosterone gel.

INTRODUCTION: Clomiphene citrate is employed off-label in men who have low testosterone and for the restoration of sperm counts in men who have used exogenous testosterone. Clomiphene is a mixture of two diastereoisomers: zuclomiphene and enclomiphene. We evaluated enclomiphene citrate in men with secondary hypogonadism. AIM: Our aim was to compare oral enclomiphene citrate as an alternative to topical testosterone. MAIN OUTCOME MEASURES: Blood levels of total testosterone (TT), estradiol, follicle-stimulating hormone (FSH), luteinizing hormone (LH), sex hormone binding globulin, thyroid stimulation hormone, prolactin, and insulin-like growth factor 1 IGF-1 were measured at certain times after treatment with each agent. Sperm parameters were determined at the same visits. Free testosterone (FT) was calculated. METHODS: This was a proof-of-principle, randomized, open-label, fixed dose, active-control, two-center phase IIB study in 12 men with secondary hypogonadism treated previously with topical testosterone. RESULTS: After discontinuation of topical testosterone, morning TT values averaged 165 ± 66 pg/dL. After 3 months, there was a significant rise in men receiving enclomiphene citrate and gel that was sustained for 3 months. At 6 months, TT levels were 545 ± 268 and 525 ± 256 pg/dL for groups receiving the gel and enclomiphene citrate, respectively. Only men in the enclomiphene citrate group demonstrated increased LH and FSH. TT decreased one month posttreatment to pretreatment values. Enclomiphene citrate elevated sperm counts in seven out of seven men at 3 months and six out of six men at 6 months with sperm concentrations in the 75-334 × 10(6) /mL range. The gel was ineffective in raising sperm counts above 20 × 10(6) /mL for all five men at 3 months and raised counts in only two or five men at 6 months. At follow-up, only enclomiphene citrate treatment was associated with elevated sperm counts. CONCLUSIONS: Enclomiphene citrate increased testosterone and sperm counts. Concomitant changes in LH and FSH suggest normalization of endogenous testosterone production and restoration of sperm counts through the hypothalamic-pituitary-testicular axis.

Clomiphene citrate and enclomiphene for the treatment of hypogonadal androgen deficiency.

Hypogonadism has a number of important clinical consequences related to androgen deficiency and impaired spermatogenesis. The cause of this condition is multifactorial and can result from hypothalamic, pituitary or gonadal dysfunction as well as factors that affect hormonal signaling along the hypothalamic-pituitary-gonadal axis. While testosterone replacement is the most common treatment, it can paradoxically lead to infertility, and may be a less physiologic therapy for patients with secondary hypogonadism due to pituitary dysfunction. Clomiphene citrate, and its derivatives, may allow for restoration of gonadal function by restoring physiologic pituitary function in a subset of patients with hypogonadism.

Enclomiphene, an estrogen receptor antagonist for the treatment of testosterone deficiency in men.

Enclomiphene (Androxal), in development by Repros Therapeutics Inc, is a non-steroidal estrogen receptor antagonist that promotes gonadotropin-dependent testosterone secretion by the testes. Enclomiphene constitutes the trans-stereoisomer of clomiphene citrate, a drug that has been widely prescribed for several decades for the treatment of female ovulatory dysfunction. Because of the antagonistic effects of enclomiphene, the drug has the potential to increase serum testosterone levels in men with secondary hypogonadism by restoring physiological endogenous testosterone secretion while maintaining testicular volume and, potentially, spermatogenesis. In clinical trials conducted to date, enclomiphene demonstrated significant efficacy in the physiological restoration of testosterone levels in males with secondary hypogonadism. The compound also exhibited an unanticipated favorable effect on fasting plasma glucose; this result has been accompanied by rapidly accumulating evidence from other researchers for a bidirectional relationship between low serum testosterone and obesity/metabolic syndrome (syndrome X) in men. Short-term clinical safety data for enclomiphene have been satisfactory and equivalent to safety data for testosterone gels and placebo. Enclomiphene demonstrates promise in the management of secondary hypogonadism associated with obesity, metabolic syndrome and, possibly, infertility, and should undergo placebo-controlled, randomized clinical trials for these indications.

Evaluation of the relationship between plasma concentrations of en- and zuclomiphene and induction of ovulation in anovulatory women being treated with clomiphene citrate.

OBJECTIVE: To investigate the relationship between the plasma concentrations of clomiphene citrate (CC) isomers zu- (Zu) and enclomiphene (En), and ovulation outcome. DESIGN: Prospective, cohort study. SETTING: Reproductive medicine and fertility center in a university teaching hospital, United Kingdom. PATIENT(S): Forty-two women with World Health Organization type 2 infertility. INTERVENTION(S): The clinical and biochemical features of patients who were about to start CC for induction of ovulation were recorded. Plasma concentration of Zu and En were monitored at three points (days 2, 8, and 21) throughout the treatment cycle(s). MAIN OUTCOME MEASURE(S): Ovulation. RESULT(S): Thirty-nine patients completed the study. Both En and Zu accumulated throughout treatment. Among the 36 responders, there was no statistically significant relationship between the clinical and biochemical characteristics of the patients, En or Zu concentrations, and the dose required to induce ovulation. Moreover, the Zu and En concentrations were not different in the three patients who failed to respond. CONCLUSION: The concentrations of En and Zu in plasma, on their own or in combination with other covariates (e.g., weight, body mass index, free androgen index), are not a predictor of the ovulation response to CC or of the dose requirement. Further studies are needed to explore the role of additional covariates, including the presence of active metabolites, and the balance of the effects of En and Zu.

Single-dose pharmacokinetic study of clomiphene citrate isomers in anovular patients with polycystic ovary disease.

The pharmacokinetics of the zuclomiphene (Zu) and enclomiphene (En) isomers of clomiphene citrate following a single oral dose (50 mg) were characterized for the first time in patients receiving the drug (ie, infertile women with polycystic ovary syndrome). Plasma concentrations of Zu and En were measured in 9 patients from the second day of their menstrual cycle (day 1 of dosing) up to 21 days. The mean (+/- coefficient of variation) of C(max), t(max), and AUC of Zu was 15 +/- 41 ng/mL, 7 +/- 87 h, and 1289 +/- 34 ng/mL.h (AUC(0-456 h)), and that of En was 15 +/- 18 ng/mL, 3 +/- 68 h, and 65 +/- 35 ng/ml.h (AUC(0-72h)), respectively. These parameters appeared to be different for Zu from those reported previously in healthy participants, except for t(max). The pharmacokinetic parameters of En in patients with polycystic ovary syndrome were not generally different from the healthy subjects. The effect of obesity on Zu kinetics was stronger than that on En. The conventional model-dependent pharmacokinetics of clomiphene citrate isomers could not be determined due to a very flat terminal half-life and the long-tailed residence time, signifying the lipophilic nature and potentially extensive distribution of the compound.

CYP2D6 is primarily responsible for the metabolism of clomiphene.

Clomiphene is a first line treatment for anovulation, a common cause of infertility. Response to clomiphene is variable and unpredictable. Tamoxifen is structurally related to clomiphene, and also shows considerable variation in response. CYP2D6 and CYP3A4 are major contributors to the metabolism of tamoxifen. The aim of the present work was to define the role of CYP2D6 and CYP3A4 in the in vitro metabolism of enclomiphene, regarded by some as the more active isomer of clomiphene. Enclomiphene (25 microM) was incubated with human liver microsomes (from 4 extensive (EM) and 1 poor metaboliser with respect to CYP2D6) and with microsomes from lymphoblastoid cells expressing CYP2D6. Microsomes from all the EM livers and recombinant CYP2D6 metabolised enclomiphene (the disappearance of drug ranged from 40-60%). No metabolism was detected in microsomes from the PM liver. Quinidine (1 microM) completely inhibited the metabolism of enclomiphene by all the EM livers and by recombinant CYP2D6 (p<0.001, one way ANOVA). Ketoconazole (2 microM) had no significant effect on enclomiphene metabolism in 3 out of the 4 EM livers. The extent of enclomiphene metabolism was correlated with the amount of CYP2D6 present (p<0.001, Pearson correlation test). The findings indicate that CYP2D6 is primarily responsible for the metabolism of enclomiphene.

Minimal ovarian stimulation with clomiphene citrate: a large-scale retrospective study.

Enclomiphene, an isomeric component of clomiphene citrate, acts antagonistically to the oestradiol receptor at the hypothalamus level, inhibiting both negative and positive feedback, and resulting in the induction of ovarian stimulation and suppression of ovulation. The minimal ovarian stimulation protocol takes full advantage of these characteristics of clomiphene citrate. Administration of 50 mg clomiphene citrate is initiated on cycle day 3, and from day 8 patients receive 150 IU of FSH every other day. When the size of the dominant follicle and the oestradiol concentration reach the predefined values, gonadotrophin-releasing hormone agonist is administered to induce follicular maturation. Oocytes are then retrieved 32-35 h later. Because the short half-life of enclomiphene (24 h) is of critical importance in this protocol, it is necessary to continue oral administration of clomiphene citrate until the day before maturation is triggered. Of all 43,433 cycles initiated, the rates for oocyte retrieval and embryo cleavage were 83 and 64% respectively. The mean number of oocytes retrieved was 2.2. The rates for live births, miscarriages, and ectopic pregnancies, in relation to initiated cycles, including cases of frozen-thawed transfer, were 11.1, 3.4 and 0.2% respectively.

Determination by liquid chromatography-mass spectrometry of clomiphene isomers in the plasma of patients undergoing treatment for the induction of ovulation.

A rapid, sensitive and selective LC-MS method is described for the simultaneous determination of zuclomiphene and enclomiphene in plasma from patients undergoing treatment with clomiphene citrate for the induction of ovulation. Samples spiked with N-didesmethyltamoxifen, the internal standard, were extracted into methyl tertiary butyl ether. The compounds were separated on a Luna C(18) analytical column, and a mobile phase of methanol-water (70:30 v/v) containing 0.05% trifluoroacetic acid at a flow rate of 1ml/min. The limits of determination were 35pg/ml and 7pg/ml for zu- and enclomiphene, respectively. Within-day coefficients of variation ranged from 2.1% to 7.2%.

Ovulation induction by antiestrogens in an Indian tropical vespertillionid bat, Scotophilus heathi.

The ovulation induction property of ICI 182,780 a pure antiestrogen and enclomiphene citrate (ENC) was carried out in Scotophilus heathi, an Indian tropical vespertillionid bat, during December to February i.e., preovulatory period. This bat ovulates two ova naturally and shows ovulatory asynchrony. The study showed that 100 ìg of ENC followed by 10 IU hCG resulted in significantly lower number of ovulation. Whereas, the pure antiestrogen ICI 182,780 at a dose of 100 ìg followed by 10 IU hCG resulted in ovulation induction (4.2 +/- 0.4), which is significantly different in comparison to other groups. This is possibly the first report of ovulation induction using this pure antiestrogen i.e., ICI 182,780 in any bat as well as in any animal model that exhibits temporary anovulation similar to polycystic ovary disease (PCOD). This antiestrogen may be useful to induce ovulation in PCOD patients.