Feedback control of luteinizing hormone and follicle-stimulating hormone secretion by testosterone and estradiol in men: physiological and clinical implications

A Review on the Use of Letrozole in Female and Male Infertility

Infertility in developing countries is a distinct and complex problem that disproportionately affects women. Though not a physically restraining disease, it causes a huge social burden on the emotional, financial, and psychosocial quotients of those who suffer from it. Assisted reproductive procedures are frequently used to treat infertility. Years ago, the emergence of ovulation induction represented a significant advancement in treating female infertility. Letrozole, an aromatase inhibitor, is a potential therapy for ovulation induction. Numerous clinical conditions, including anovulatory infertility, polycystic ovarian syndrome, unexplained infertility, and early stages of endometriosis-related infertility, as well as many with improved live birth rates, have been proven to benefit from letrozole treatment. Letrozole is a superior alternative to the widely utilized ovulation induction with clomiphene citrate. While clomiphene citrate has certain limitations, letrozole successfully overcomes these limitations because of its lack of prolonged anti-estrogenic activity, short half-life, and lack of estrogen receptor activation. In most cases, this results in mono-follicular development and excellent live birth rates. According to the most recent research, letrozole can be used as the first-line therapy to treat infertility caused by polycystic ovarian syndrome and other causes. Letrozole is also emerging as a possible treatment for male infertility of unknown cause, proving to be an effective way of influencing hormonal profiles and increasing various seminal parameters such as sperm motility and concentration, as it inhibits aromatization affecting the feedback mechanism to the hypothalamus. This review focuses on our current knowledge of the uses of letrozole for female and male infertility, its mechanisms, and its benefits.

Understanding and managing the suppression of spermatogenesis caused by testosterone replacement therapy (TRT) and anabolic–androgenic steroids (AAS)

Use of testosterone replacement therapy (TRT) and anabolic–androgenic steroids (AAS) has increased over the last 20 years, coinciding with an increase in men presenting with infertility and hypogonadism. Both agents have a detrimental effect on spermatogenesis and pose a clinical challenge in the setting of hypogonadism and infertility. Adding to this challenge is the paucity of data describing recovery of spermatogenesis on stopping such agents. The unwanted systemic side effects of these agents have driven the development of novel agents such as selective androgen receptor modulators (SARMs). Data showing natural recovery of spermatogenesis following cessation of TRT are limited to observational studies. Largely, these have shown spontaneous recovery of spermatogenesis after cessation. Contemporary literature suggests the time frame for this recovery is highly variable and dependent on several factors including baseline testicular function, duration of drug use and age at cessation. In some men, drug cessation alone may not achieve spontaneous recovery, necessitating hormonal stimulation with selective oestrogen receptor modulators (SERMs)/gonadotropin therapy or even the need for assisted reproductive techniques. However, there are limited prospective randomized data on the role of hormonal stimulation in this clinical setting. The use of hormonal stimulation with agents such as gonadotropins, SERMs, aromatase inhibitors and assisted reproductive techniques should form part of the counselling process in this cohort of hypogonadal infertile men. Moreover, counselling men regarding the detrimental effects of TRT/AAS on fertility is very important, as is the need for robust randomized studies assessing the long-term effects of novel agents such as SARMs and the true efficacy of gonadotropins in promoting recovery of spermatogenesis.

A systematic review and meta-analysis of clinical trials implementing aromatase inhibitors to treat male infertility

Aromatase activity has commonly been associated with male infertility characterized by testicular dysfunction with low serum testosterone and/or testosterone to estradiol ratio. In this subset of patients, and particularly in those with hypogonadism, elevated levels of circulating estradiol may establish a negative feedback on the hypothalamic-pituitary-testicular axis by suppressing follicle-stimulating hormone (FSH) and luteinizing hormone (LH) production and impaired spermatogenesis. Hormonal manipulation via different agents such as selective estrogen modulators or aromatase inhibitors to increase endogenous testosterone production and improve spermatogenesis in the setting of infertility is an off-label option for treatment. We carried out a systematic review and meta-analysis of the literature of the past 30 years in order to evaluate the benefits of the use of aromatase inhibitors in the medical management of infertile/hypoandrogenic males. Overall, eight original articles were included and critically evaluated. Either steroidal (Testolactone) or nonsteroidal (Anastrozole and Letrozole) aromatase inhibitors were found to statistically improve all the evaluated hormonal and seminal outcomes with a safe tolerability profile. While the evidence is promising, future prospective randomized placebo-controlled multicenter trials are necessary to better define the efficacy of these medications.

A Testis-Specific Long Noncoding RNA, Start, Is a Regulator of Steroidogenesis in Mouse Leydig Cells

The testis expresses many long noncoding RNAs (lncRNAs), but their functions and overview of lncRNA variety are not well understood. The mouse Prss/Tessp locus contains six serine protease genes and two lncRNAs that have been suggested to play important roles in spermatogenesis. Here, we found a novel testis-specific lncRNA, Start (Steroidogenesis activating lncRNA in testis), in this locus. Start is 1822 nucleotides in length and was found to be localized mostly in the cytosol of germ cells and Leydig cells, although nuclear localization was also observed. Start-knockout (KO) mice generated by the CRISPR/Cas9 system were fertile and showed no morphological abnormality in adults. However, in adult Start-KO testes, RNA-seq and qRT-PCR analyses revealed an increase in the expression of steroidogenic genes such as Star and Hsd3b1, while ELISA analysis revealed that the testosterone levels in serum and testis were significantly low. Interestingly, at 8 days postpartum, both steroidogenic gene expression and testosterone level were decreased in Start-KO mice. Since overexpression of Start in two Leydig-derived cell lines resulted in elevation of the expression of steroidogenic genes including Star and Hsd3b1, Start is likely to be involved in their upregulation. The increase in expression of steroidogenic genes in adult Start-KO testes might be caused by a secondary effect via the androgen receptor autocrine pathway or the hypothalamus-pituitary-gonadal axis. Additionally, we observed a reduced number of Leydig cells at 8 days postpartum. Collectively, our results strongly suggest that Start is a regulator of steroidogenesis in Leydig cells. The current study provides an insight into the overall picture of the function of testis lncRNAs.

Effect of Letrozole on sperm parameters, chromatin status and ROS level in idiopathic Oligo/Astheno/Teratozoospermia

BACKGROUND

This study investigates the effect of letrozole on hormone profiles, semen parameters, body mass index (BMI), degree of oxidative stress and sperm chromatin integrity in men with idiopathic oligo/astheno/teratozoospermia (iOAT) and T:E₂ ratio ≤ 10.

MATERIALS AND METHODS

This study is a longitudinal, prospective, interventional and open-labelled clinical trial. Semen samples were collected from 20 iOAT men with low serum testosterone (T) to estradiol (E₂) ratio (T:E₂ ratio ≤ 10). The participants were treated with 2.5 mg letrozole orally per day for 3 months. Then, sperm parameters, hormone profiles, BMI, chromatin integrity and intracellular reactive oxygen species (ROS) level were assessed pre- and post- treatment. The chromatin integrity was evaluated by assessment of DNA fragmentation (with TUNEL assay) and protamine deficiency (with Chromomycin A3, CMA3). Also, the intracellular ROS levels were investigated by 2', 7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. Finally, the differences between the parameters evaluated before and after letrozole treatment were analyzed with the t-test and the Wilcoxon signed-rank test.

RESULTS

Sperm concentration, percentage of sperm motility and its normal morphology increased significantly after letrozole treatment. Moreover, serum testosterone level increased but estradiol level decreased significantly following treatment. The mean of T:E2 ratio improved 1600%. Also, letrozole treatment significantly reduced the percentage of sperm TUNEL positivity and sperm CMA3 positivity. While no significant difference was observed between intracellular ROS levels and BMI before and after treatment. Finally, as a notable result, four spontaneous pregnancies (20%) were achieved after treatment.

CONCLUSIONS

Letrozole treatment can effectively increase spontaneous pregnancies by improving sperm parameters and sperm chromatin integrity in men with iOAT and T:E2 ratio ≤ 10.

TRIAL REGISTRATION

Trial registration: IRCT, IRCT20191030045283N1. Registered 16 November 2019 - Retrospectively registered, https://fa.irct.ir/user/trial/43484/view.

The Metabolism, Analysis, and Targeting of Steroid Hormones in Breast and Prostate Cancer

Breast and prostate cancers are malignancies in which steroid hormones drive cellular proliferation. Over the past century, this understanding has led to successful treatment strategies aimed to inhibit hormone-mediated tumor growth. Nonetheless, disease relapse and progression still pose significant clinical problems, with recurrent and metastatic tumors often exhibiting resistance to current drug therapies. The central role of androgens and estrogens in prostate and breast cancer etiology explains not only why endocrine therapies are often initially successful but also why many tumors ultimately become resistant. It is hypothesized that reducing the concentration of active hormones in the systemic circulation may be insufficient to block cancer progression, as this action selects for tumor cells that can generate active steroids from circulating precursors. This review aims to highlight the currently known differences of steroid biosynthesis in normal physiology versus hormone-dependent cancers, modern approaches to the assessment and targeting of these pathways, and priorities for future research.

Medical treatment of male infertility

The majority of male infertility is idiopathic. However, there are multiple known causes of male infertility, and some of these causes can be treated medically with high success rates. In cases of idiopathic or genetic causes of male infertility, medical management is typically empirical; in most instances medical therapy represents off-label use that is not specifically approved by the FDA. Understanding the hypothalamic-pituitary-gonadal (HPG) axis and the effect of estrogen excess is critical for the assessment and treatment of male infertility. The use of certain medical treatment has been associated with an increase in sperm production or motility, and primarily focuses on optimizing testosterone (T) production from the Leydig cells, increasing follicle-stimulating hormone (FSH) levels to stimulate Sertoli cells and spermatogenesis, and normalizing the T to estrogen ratio.

Coadministration of anastrozole sustains therapeutic testosterone levels in hypogonadal men undergoing testosterone pellet insertion

INTRODUCTION

Current U.S. Food and Drug Administration-approved therapies for hypogonadism involve testosterone (T) replacement. Testosterone pellets (TP) require a minor office procedure every 3 to 4 months. The need for repeated insertions increases the likelihood of a complication. Anastrozole (AZ) is an aromatase inhibitor that has been used off-label for the treatment of male hypogonadism. AZ increases T levels by lowering serum estradiol (E2) levels and increasing gonadotropin (GTP) levels.

AIM

We hypothesized that the concomitant use of AZ with TP insertions would sustain therapeutic T levels and increase the interval between TP insertions.

METHODS

Men treated with TP for hypogonadism at an academic center were offered AZ (1 mg/day) at the time of TP reinsertion as a way of potentially decreasing the frequency of TP insertions. Total T (TT), free T (FT), sex hormone binding globulin, E2, luteinizing hormone (LH), and follicle-stimulating hormone FSH levels were obtained prior to T replacement and at 6 and 15 weeks from TP insertion. Men were re-implanted at 16 weeks if their TT levels were less than 350 ng/dL and their symptoms recurred. We retrospectively reviewed our records of men who underwent TP, TP, and AZ from 2011 to 2012. Demographics, TT, FT, LH, FSH, and E2 levels were recorded. Data were analyzed with anova and a Tukey's test.

MAIN OUTCOME MEASURE

TT level at 6, 15, or >15 weeks from TP insertion.

RESULTS

Thirty-eight men with 65 insertions were analyzed. The TP AZ group had significantly higher TT and FT levels than the TP group at >120 days (P < 0.05). The TP group had significantly higher E2 levels at all time points (P < 0.01). GTP levels remained stable in the TP AZ group. Average time to reinsertion in TP AZ was 198 days vs. 128 days in the TP group.

CONCLUSION

Men on TP AZ maintain therapeutic T levels longer than men on TP alone and have significantly less GTP suppression.

Aromatase inhibitors for male infertility

Some men with severely defective sperm production commonly have excess aromatase activity, reflected by low serum testosterone and relatively elevated estradiol levels. Aromatase inhibitors can increase endogenous testosterone production and serum testosterone levels. Treatment of infertile males with the aromatase inhibitors testolactone, anastrazole, and letrozole has been associated with increased sperm production and return of sperm to the ejaculate in men with non-obstructive azoospermia. Use of the aromatase inhibitors anastrazole (1 mg/day) and letrozole (2.5 mg/day) represent off-label use of these agents for impaired spermatogenesis in men with excess aromatase activity (abnormal testosterone/estradiol [T/E] ratios). Side effects have rarely been reported. Randomized controlled trials are needed to define the magnitude of benefit of aromatase inhibitor treatment for infertile men.

Treatment of anabolic-androgenic steroid dependence: Emerging evidence and its implications

Currently, few users of anabolic-androgenic steroids (AAS) seek substance abuse treatment. But this picture may soon change substantially, because illicit AAS use did not become widespread until the 1980s, and consequently the older members of this AAS-using population - those who initiated AAS as youths in the 1980s - are only now reaching middle age. Members of this group, especially those who have developed AAS dependence, may therefore be entering the age of risk for cardiac and psychoneuroendocrine complications sufficient to motivate them for substance abuse treatment. We suggest that this treatment should address at least three etiologic mechanisms by which AAS dependence might develop. First, individuals with body image disorders such as "muscle dysmorphia" may become dependent on AAS for their anabolic effects; these body image disorders may respond to psychological therapies or pharmacological treatments. Second, AAS suppress the male hypothalamic-pituitary-gonadal axis via their androgenic effects, potentially causing hypogonadism during AAS withdrawal. Men experiencing prolonged dysphoric effects or frank major depression from hypogonadism may desire to resume AAS, thus contributing to AAS dependence. AAS-induced hypogonadism may require treatment with human chorionic gonadotropin or clomiphene to reactivate neuroendocrine function, and may necessitate antidepressant treatments in cases of depression inadequately responsive to endocrine therapies alone. Third, human and animal evidence indicates that AAS also possess hedonic effects, which likely promote dependence via mechanisms shared with classical addictive drugs, especially opioids. Indeed, the opioid antagonist naltrexone blocks AAS dependence in animals. By inference, pharmacological and psychosocial treatments for human opioid dependence might also benefit AAS-dependent individuals.

History of aromatase: saga of an important biological mediator and therapeutic target

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.

Elevated dehydroepiandrosterone sulfate levels as the reproductive phenotype in the brothers of women with polycystic ovary syndrome

There is an inherited susceptibility to polycystic ovary syndrome (PCOS). Some investigators have suggested that premature male-pattern balding is a male phenotype in PCOS families, but this remains controversial. We recently reported evidence for an autosomal monogenic abnormality in ovarian and adrenal steroidogenesis in the sisters of women with PCOS. We performed this study to determine whether we could identify a clinical or biochemical phenotype in the brothers of women with PCOS. One hundred nineteen brothers of 87 unrelated women with PCOS and 68 weight- and ethnicity-comparable unrelated control men were examined and had fasting blood samples obtained. The odds of balding (Hamilton score > or = V) did not differ in the brothers of PCOS women compared with control men. Brothers of women with PCOS had significantly elevated dehydroepiandrosterone sulfate (DHEAS) levels [brothers 3035 +/- 1132 ng/ml (mean +/- SD) vs. control men 2494 +/- 1172 ng/ml; P < 0.05]. There was a significant positive linear relationship between DHEAS levels in PCOS probands and their brothers (r = 0.35; P = 0.001). There was no significant bimodal distribution in DHEAS levels, and there were no significant differences in other parameters in brothers of PCOS women with high DHEAS levels compared with those with low DHEAS levels. There is familial clustering of elevated DHEAS levels in the brothers of women with PCOS, suggesting that this is a genetic trait. This might reflect the same underlying defect in steroidogenesis that we found in the sisters of women with PCOS. Balding was not increased in the brothers of women with PCOS. We conclude that there is a biochemical reproductive endocrine phenotype in men in PCOS families.

A psychoendocrine study in male paranoid schizophrenics with delusional ideas of homosexual content

The serum prolactin (PRL), luteinizing hormone (LH), testosterone (T) and estradiol (E) levels were investigated in a group of male paranoid schizophrenics with delusional ideas of homosexual content, in a group of male paranoid schizophrenics without delusional ideas of homosexual content, and in a group of healthy, male heterosexual subjects. Only male paranoid schizophrenics with delusional ideas of homosexual content had significantly lower serum PRL values and significantly higher serum E levels than those of the age-matched group of normal, male heterosexual controls; also, these patients tended to have higher (though not to a statistically significant degree) serum LH and T levels than those of normal controls. Findings of this study are discussed within the framework of the possible involvement of endocrine factors in the occurrence of delusional ideas of homosexual content in male patients with paranoid schizophrenia.