Genetic determinants of serum testosterone concentrations in men

Genetic determinants of plasma testosterone in male blood donors are associated with altered red blood cell characteristics and survival in cold storage and after transfusion

Genetic mutations in genes regulating plasma testosterone in men may interfere with effective erythropoiesis, and may result in red blood cell (RBC) dysfunction and hemolysis. The aim of this study was to identify genetic polymorphisms in male donors that regulate plasma testosterone and impact RBC survival in cold storage and after transfusion. We evaluated nine single nucleotide polymorphisms (SNPs) previously reported to be associated with circulating testosterone in male plasma. These SNPs were linked with donor-component-recipient databases (NIH REDS program) to determine SNP associations with donor RBC hematological indices, osmotic and oxidative hemolysis, and RBC transfusion effectiveness defined as adjusted hemoglobin increments (delta hemoglobin, ΔHb) following a single RBC unit transfusion. Four of the nine testosterone SNPs were located on the X chromosome, of which two (rs7057002, rs73629199) were significantly associated with reduced hemoglobin increments (0.2 and 0.3 g/dL, respectively) compared with reference alleles in transfused recipients. Seven of the nine testosterone SNPs were associated with significant changes in RBC susceptibility to osmotic hemolysis including a missense mutation in the major plasma carrier of testosterone (SHBG, rs6259), and four SNPs with changes in oxidative hemolysis. Four SNPs were associated with decreased RBC count, hemoglobin, and hematocrit. Ancestry/ethnicity-specific (African and Hispanic) associations were observed between two SNPs (rs7057002, rs7879462) and oxidative hemolysis. Genetic determinants of plasma testosterone in male donors significantly impact the quality and transfusion effectiveness of cold stored RBCs. Testosterone SNPs associated with decreased RBC transfusion effectiveness may have clinical implications and warrant further revaluation.

Sex hormone-binding globulin and its critical role in prostate cancer: A comprehensive review

Prostate cancer (PC) is a common and widespread cancer that affects men globally. A complicated interaction of hormonal variables influences its development. Sex hormone-binding globulin (SHBG) is a crucial element in controlling the availability of sex hormones, especially androgens, which have a notable impact on the development and progression of PC. SHBG controls the levels of free, active androgens in the body, which helps regulate androgen-dependent processes associated with PC. The equilibrium between SHBG and androgens plays a critical role in maintaining the stability of the prostate. When this balance is disrupted, it is associated with the development and advancement of PC. The processes responsible for SHBG's role in PC are complex and have multiple aspects. SHBG primarily binds to androgens, preventing them from interacting with androgen receptors (ARs) in prostate cells. It reduces the activation of androgen signaling pathways essential for tumor development and survival. In addition, SHBG can directly affect prostate cells by interacting with specific receptors on the cell surface. This review thoroughly examines the role of SHBG in PC, including its physiological activities, methods of action, and clinical consequences.

Obesity-Dependent Association of the rs10454142 PPP1R21 with Breast Cancer

The purpose of this work was to find a link between the breast cancer (BC)-risk effects of sex hormone-binding globulin (SHBG)-associated polymorphisms and obesity. The study was conducted on a sample of 1498 women (358 BC; 1140 controls) who, depending on the presence/absence of obesity, were divided into two groups: obese (119 BC; 253 controls) and non-obese (239 BC; 887 controls). Genotyping of nine SHBG-associated single nucleotide polymorphisms (SNP)-rs17496332 PRMT6, rs780093 GCKR, rs10454142 PPP1R21, rs3779195 BAIAP2L1, rs440837 ZBTB10, rs7910927 JMJD1C, rs4149056 SLCO1B1, rs8023580 NR2F2, and rs12150660 SHBG-was executed, and the BC-risk impact of these loci was analyzed by logistic regression separately in each group of obese/non-obese women. We found that the BC-risk effect correlated by GWAS with the SHBG-level polymorphism rs10454142 PPP1R21 depends on the presence/absence of obesity. The SHBG-lowering allele C rs10454142 PPP1R21 has a risk value for BC in obese women (allelic model: CvsT, OR = 1.52, 95%CI = 1.10-2.11, and pperm = 0.013; additive model: CCvsTCvsTT, OR = 1.71, 95%CI = 1.15-2.62, and pperm = 0.011; dominant model: CC + TCvsTT, OR = 1.95, 95%CI = 1.13-3.37, and pperm = 0.017) and is not associated with the disease in women without obesity. SNP rs10454142 PPP1R21 and 10 proxy SNPs have adipose-specific regulatory effects (epigenetic modifications of promoters/enhancers, DNA interaction with 51 transcription factors, eQTL/sQTL effects on five genes (PPP1R21, RP11-460M2.1, GTF2A1L, STON1-GTF2A1L, and STON1), etc.), can be "likely cancer driver" SNPs, and are involved in cancer-significant pathways. In conclusion, our study detected an obesity-dependent association of the rs10454142 PPP1R21 with BC in women.

Sex-Hormone-Binding Globulin Gene Polymorphisms and Breast Cancer Risk in Caucasian Women of Russia

In our work, the associations of GWAS (genome-wide associative studies) impact for sex-hormone-binding globulin (SHBG)-level SNPs with the risk of breast cancer (BC) in the cohort of Caucasian women of Russia were assessed. The work was performed on a sample of 1498 women (358 BC patients and 1140 control (non BC) subjects). SHBG correlated in previously GWAS nine polymorphisms such as rs780093 GCKR, rs17496332 PRMT6, rs3779195 BAIAP2L1, rs10454142 PPP1R21, rs7910927 JMJD1C, rs4149056 SLCO1B1, rs440837 ZBTB10, rs12150660 SHBG, and rs8023580 NR2F2 have been genotyped. BC risk effects of allelic and non-allelic SHBG-linked gene SNPs interactions were detected by regression analysis. The risk genetic factor for BC developing is an SHBG-lowering allele variant C rs10454142 PPP1R21 ([additive genetic model] OR = 1.31; 95%CI = 1.08-1.65; pperm = 0.024; power = 85.26%), which determines 0.32% of the cancer variance. Eight of the nine studied SHBG-related SNPs have been involved in cancer susceptibility as part of nine different non-allelic gene interaction models, the greatest contribution to which is made by rs10454142 PPP1R21 (included in all nine models, 100%) and four more SNPs-rs7910927 JMJD1C (five models, 55.56%), rs17496332 PRMT6 (four models, 44.44%), rs780093 GCKR (four models, 44.44%), and rs440837 ZBTB10 (four models, 44.44%). For SHBG-related loci, pronounced functionality in the organism (including breast, liver, fibroblasts, etc.) was predicted in silico, having a direct relationship through many pathways with cancer pathophysiology. In conclusion, our results demonstrated the involvement of SHBG-correlated genes polymorphisms in BC risk in Caucasian women in Russia.

Revisiting Carl Jung's archetype theory a psychobiological approach

This paper delves into the concept of archetypes, universal patterns of behavior and cognition, and proposes a novel tripartite model distinguishing between structural, regulatory, and representational archetypes. Drawing on insights from code biology, neuroscience, genetics, and epigenetics, the model provides a nuanced framework for understanding archetypes and their role in shaping cognition and behavior. The paper also explores the interplay between these elements to express representational archetypes. Furthermore, it addresses the informational capacity of the genome and its influence on post-natal development and the psyche. The paper concludes by discussing the future trajectory of psychology, emphasizing the need for an integrative approach that combines our understanding of social constructs with insights into our inherent organizational propensities or archetypes. This exploration holds the potential to advance our understanding of the human condition.

Genetic regulation of testosterone level in overweight males from the Kazakh population and its association with hypogonadism

Male hypogonadism and erectile dysfunction in different populations are associated with excess body weight. A key aspect in most studies is the metabolism of sexual hormones, primarily testosterone. At the same time, the binding protein sex hormone binding globulin (SHBG) can play a large role, as it determines the ratio of total and bioavailable testosterone in blood, i.e. both the hormone content and level of its production. Recent research has identified common mutations that affect SHBG levels, such as the rs727428 polymorphic locus, which is associated with alterations in histone protein function, affecting the regulation of ribonucleic acid (RNA) protein SHBG synthesis. Similar relationships have been observed for prevalent mutations, including rs5934505 and rs10822184, in diverse populations. This study involved 300 individuals of Kazakh nationality from the Eastern Kazakhstan region, examining three polymorphic variants of the SHBG gene (rs727428, rs5934505, and rs10822184). The participants were categorized into three groups: individuals with hypogonadism and obesity (group 1, n=85), those with excess body weight but no hypogonadism (group 2, n=70), and individuals with neither excess body weight nor hypogonadism (group 3, n=145). The frequency of mutant gene alleles impacting GPS (SHBG) synthesis in the Kazakh population was notably high, comparable to European and South-East Asian populations. However, the association between excess body weight and these mutations exhibited varying patterns. Hypogonadism was linked to decreased GPS levels, strongly correlating with total testosterone but not bioavailable testosterone. The retention of sexual functions in overweight men was not always directly related to BMI levels and GPS concentrations.

Genetic analyses implicate complex links between adult testosterone levels and health and disease

BACKGROUND

Testosterone levels are linked with diverse characteristics of human health, yet, whether these associations reflect correlation or causation remains debated. Here, we provide a broad perspective on the role of genetically determined testosterone on complex diseases in both sexes.

METHODS

Leveraging genetic and health registry data from the UK Biobank and FinnGen (total N = 625,650), we constructed polygenic scores (PGS) for total testosterone, sex-hormone binding globulin (SHBG) and free testosterone, associating these with 36 endpoints across different disease categories in the FinnGen. These analyses were combined with Mendelian Randomization (MR) and cross-sex PGS analyses to address causality.

RESULTS

We show testosterone and SHBG levels are intricately tied to metabolic health, but report lack of causality behind most associations, including type 2 diabetes (T2D). Across other disease domains, including 13 behavioral and neurological diseases, we similarly find little evidence for a substantial contribution from normal variation in testosterone levels. We nonetheless find genetically predicted testosterone affects many sex-specific traits, with a pronounced impact on female reproductive health, including causal contribution to PCOS-related traits like hirsutism and post-menopausal bleeding (PMB). We also illustrate how testosterone levels associate with antagonistic effects on stroke risk and reproductive endpoints between the sexes.

CONCLUSIONS

Overall, these findings provide insight into how genetically determined testosterone correlates with several health parameters in both sexes. Yet the lack of evidence for a causal contribution to most traits beyond sex-specific health underscores the complexity of the mechanisms linking testosterone levels to disease risk and sex differences.

Usefulness of routine assessment of free testosterone for the diagnosis of functional male hypogonadism

OBJECTIVE

To investigate whether routine assessment of free testosterone improves the diagnostic accuracy of functional hypogonadism.

METHODS

Total and free testosterone (calculated on SHBG levels) were determined in 188 patients with sexual symptoms and 184 with infertility.

RESULTS

Hypogonadism (calculated free testosterone <63 pg/ml) was found in 47/188 (25.0%) patients with sexual symptoms and in 21/184 (11.4%) with infertility. Total testosterone determination misdiagnosed hypogonadism in 8.4% (12/143) of men with sexual symptoms and in 2% (3/152) with infertility. In subjects with borderline total testosterone, only 24.7% (19/77) had hypogonadism confirmed by free testosterone levels. Free testosterone levels significantly correlated with age, haematocrit, gonadotropins, gynecomastia, BMI, and number of co-morbidities, whereas total testosterone associated only with the latter two. Furthermore, age, haematocrit, BMI, and the presence of erectile dysfunction and of low libido were significantly different between men with normal and low free testosterone, whereas only BMI and low libido were significantly different between patients with normal and low total testosterone.

CONCLUSION

Routine assessment of free testosterone allows a more accurate diagnosis of functional hypogonadism, especially in men with sexual symptoms. Free testosterone levels associate with clinical and biochemical parameters of androgen deficiency better than total testosterone levels.

Circulating dihydrotestosterone, testosterone, and free testosterone levels and dihydrotestosterone-to-testosterone ratios in healthy women across the menstrual cycle

OBJECTIVE

To characterize the circulating androgen levels across the menstrual cycle in healthy women using highly sensitive and accurate methods and report sex differences in the relative levels of dihydrotestosterone (DHT) to testosterone (T) levels.

DESIGN

Prospective cohort study.

SETTING

Research clinic, academic teaching hospital.

PATIENT(S)

Twenty-one healthy premenopausal women, aged 19-40 years, with regular menstrual cycles.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

Serum total T and DHT levels measured using liquid chromatography-tandem mass spectrometry, free T levels measured using a standardized equilibrium dialysis method coupled with measurement of the T levels in the dialysate using liquid chromatography-tandem mass spectrometry, and comparison of the DHT-to-T ratio between healthy women and age-matched healthy men.

RESULT(S)

The serum total and free T levels increased across the follicular phase and peaked at midcycle (total T, 43.6 ± 16.2 ng/dL; free T, 15.6 ± 11.9 pg/mL) and gradually declined in the luteal phase. The DHT level did not significantly change across the menstrual cycle. The DHT-to-T ratios were 1:4 and 1:13 in women and men, respectively.

CONCLUSION(S)

In healthy premenopausal women, the total and free T levels varied significantly across the menstrual cycle, whereas the DHT levels did not change; the peak total and free T levels in the midcycle period were higher than previously reported, underscoring the importance of establishing menstrual phase-specific reference ranges to avoid misdiagnosis of hyperandrogenism. Women have significantly higher DHT levels relative to total T than men; the significance of this sex difference in the DHT-to-T ratio needs further investigation.

Lrriq1 is an essential factor for fertility by suppressing apoptosis

PURPOSE

Leucine-rich repeats and IQ motif containing 1 (LRRIQ1) gene is reportedly associated with plasma inhibin B levels. However, the function of LRRIQ1 remains unknown. In this study, we generated Lrriq1 knockout mice (Lrriq1-/- mice) and examined the effects of LRRIQ1 on inhibin B and fertility.

METHODS

Lrriq1-/- mice were generated using CRISPR/Cas9 genome editing technology. The expression of Inhibin B was examined by Western blotting using a protein extracted from the testis of a 3-month-old male mouse. Mating experiments were conducted using 7-week-old Lrriq1-/- mice and wild-type (WT) mice to examine fertility. Sperm concentration and sperm motility were measured using 3-month-old male mice.

RESULTS

Expression analysis of inhibin B revealed that Lrriq1-/- mice exhibited reduced mRNA and protein levels of inhibin alpha (Inha), which constitutes the α subunit. In the mating experiment, the litter size of Lrriq1-/- male mice was 4.3 ± 2.9, which was significantly lower than that of WT male mice (8.3 ± 1.3) (p < 0.001). No difference in sperm count was observed between Lrriq1-/- and WT male mice; however, sperm motility (%) was significantly reduced in Lrriq1-/- mice (48.4 ± 4.9) when compared with WT mice (70.2 ± 4.7) (p < 0.001). Based on TUNEL staining, the testes and epididymal sperm of Lrriq1-/- mice showed high numbers of apoptosis-positive cells.

CONCLUSION

Lrriq1 knockout reduced sperm motility and litter size by inducing apoptosis of testicular germ cells and epididymal sperm.

Role of sex hormone-binding globulin in the free hormone hypothesis and the relevance of free testosterone in androgen physiology

According to the free hormone hypothesis, biological activity of a certain hormone is best reflected by free rather than total hormone concentrations. A crucial element in this theory is the presence of binding proteins, which function as gatekeepers for steroid action. For testosterone, tissue exposure is governed by a delicate equilibrium between free and total testosterone which is determined through interaction with the binding proteins sex hormone-binding globulin and albumin. Ageing, genetics and various pathological conditions influence this equilibrium, hereby possibly modulating hormonal exposure to the target tissues. Despite ongoing controversy on the subject, strong evidence from recent in vitro, in vivo and human experiments emphasizes the relevance of free testosterone. Currently, however, clinical possibilities for free hormone diagnostics are limited. Direct immunoassays are inaccurate, while gold standard liquid chromatography with tandem mass spectrometry (LC-MS/MS) coupled equilibrium dialysis is not available for clinical routine. Calculation models for free testosterone, despite intrinsic limitations, provide a suitable alternative, of which the Vermeulen calculator is currently the preferred method. Calculated free testosterone is indeed associated with bone health, frailty and other clinical endpoints. Moreover, the added value of free testosterone in the clinical diagnosis of male hypogonadism is clearly evident. In suspected hypogonadal men in whom borderline low total testosterone and/or altered sex hormone-binding globulin levels are detected, the determination of free testosterone avoids under- and overdiagnosis, facilitating adequate prescription of hormonal replacement therapy. As such, free testosterone should be integrated as a standard biochemical parameter, on top of total testosterone, in the diagnostic workflow of male hypogonadism.

A Shifting Relationship Between Sex Hormone-Binding Globulin and Total Testosterone Across Puberty in Boys

CONTEXT

Sex hormone-binding globulin (SHBG) is associated with levels of total testosterone (total-T), and both total-T and SHBG are associated with obesity.

OBJECTIVE

We aimed to clarify the nature of the relationship between testosterone and SHBG and improve our understanding of their relationships with obesity. We hypothesize that the hypothalamic-pituitary-gonadal axis contributes to the homeostasis of testosterone by increasing the production of gonadal testosterone through a feedback mechanism that might operate differently at different pubertal stages.

METHODS

We investigated the dynamics of the relationship between SHBG, total-T, and body mass index (BMI) throughout puberty (from age 9 to 17) using longitudinal data obtained in 507 males. The directionality of this relationship was explored using polygenic scores of SHBG and total-T, and a two-sample Mendelian Randomization (MR) in male adults.

RESULTS

Consistent with our hypothesis, we found positive relationships between SHBG and total-T at age 15 and 17 but either no relationship or a negative relationship during the earlier time points. Such shifting relationships explained age-related changes in the association between total-T and BMI. Polygenic scores of SHBG and total-T in mediation analyses and the two-sample MR in male adults suggested an effect of SHBG on total-T but also a somewhat weaker effect of total-T on SHBG. Two-sample MR also showed an effect of BMI on SHBG but no effect of SHBG on BMI.

CONCLUSION

These results clarify the nature of the relationship between testosterone and SHBG during puberty and adulthood and shed new light on their possible relationship with obesity.

In and out of unemployment-Labour market transitions and the role of testosterone

Biological processes have provided new insights into diverging labour market trajectories. This paper uses population variation in testosterone levels to explain transition probabilities into and out of unemployment. We examine labour market transitions for 2004 initially employed and 111 initially unemployed British men from the UK Household Longitudinal Study ("Understanding Society") between 2011 and 2013. We address the endogeneity of testosterone levels by using genetic variation as instrumental variables (Mendelian Randomization). We find that for both initially unemployed men as well as initially employed men, higher testosterone levels reduce the risk of unemployment. Based on previous studies and descriptive evidence, we argue that these effects are likely driven by differences in cognitive and non-cognitive skills as well as job search behaviour of men with higher testosterone levels. Our findings suggest that latent biological processes can affect job search behaviour and labour market outcomes without necessarily relating to illness and disability.

Effect of SHBG Polymorphism on the Levels of Bioavailable Testosterone and Lipid Metabolism in Older Men of the Kazakh Population

This study is aimed at investigating the effect of SHBG (rs727428; rs10822184) and LPL (rs754493647) single nucleotide polymorphisms on the concentration of the bioavailable fraction of testosterone in older men. Materials and methods To study gene mutations, 417 residents of the East Kazakhstan region of Kazakh nationality were examined. The main group included 135 men with signs of hypogonadism (AMS 37-49), and the control group consisted of 282 healthy men (AMS 17-26) of the corresponding age (p = 0.5). Single nucleotide polymorphisms rs 727428 [C / T]; rs10822184 [T / C]; rs754493647 [T / C], was determined by the TaqMan method. Results Analysis of the rs727428 polymorphism has revealed that the TT allele (rs727428) has a lower level of albumin (p = 0.03), bioavailable testosterone (p = 0.04), and free testosterone (p = 0.6) than in carriers of the CC and CT genotypes. Also, it has shown a decrease in total testosterone (p = 0.001) and an increase in SHBG levels (p = 0.07) in men with the TT genotype of the rs727428 gene polymorphism. The rs10822184 polymorphism demonstrated an increase in triglyceride and LDL levels in TT genotype (p ≤ 0.04), in comparison with CC and CT genotypes. Conclusion It has been proven that rs727428 (p = 0.001) is associated with testosterone levels and therefore can determine the concentration of bioavailable testosterone. Decreased levels of bioavailable testosterone are a sign of male hypogonadism. This study confirms the effect of rs10822184 on LDL (p = 0.01) and triglyceride (p = 0.04) levels, but its association with androgen levels has not been proven. Our results may be of interest for understanding the etiology of early development of hypogonadism and lipid metabolism disorders in men. To confirm the conclusions, a more detailed study with a large sample of men from the Kazakh population may be required.

Accurate measurement of total and free testosterone levels for the diagnosis of androgen disorders

The circulating concentrations of total and free testosterone vary substantially in people over time due to biologic factors as well as due to measurement variation. Accurate measurement of total and free testosterone is essential for making the diagnosis of androgen disorders. Total testosterone should ideally be measured in a fasting state in the morning using a reliable assay, such as liquid chromatography tandem mass spectrometry, in a laboratory that is certified by an accuracy-based benchmark. Free testosterone levels should be measured in men in whom alterations in binding protein concentrations are suspected or in whom total testosterone levels are only slightly above or slightly below the lower limit of the normal male range for testosterone.

Ageing male (part I): Pathophysiology and diagnosis of functional hypogonadism

This narrative review summarizes key points of the pathogenesis and diagnosis of the ageing-related decline of testosterone (T) in men. The condition is commonly termed late-onset hypogonadism (LOH), but because it is more often caused by other factors than chronological ageing (obesity and other comorbidities), a more appropriate term is functional hypogonadism (FH). Unlike the classical organic hypogonadism, no anatomical or genetic aberrations are found in FH, and the suppression of T is milder. Moreover, FH can be reversible if the underlying cause (e.g. obesity, chronic disease) is removed/treated. Low serum total T in connection with more specific hypogonadism-associated symptoms (primarily sexual) form the basis of the diagnosis of FH. When T concentrations are borderline, the accuracy of diagnosis can be improved by assessment of free or calculated free T, especially when suppressed SHBG levels (usually related to obesity) are likely. Current data indicate that FH (low T and sexual symptoms) is not a common condition, and it is detectable in about 2% of community-dwelling men aged 40-80 years.

Accurate Measurement and Harmonized Reference Ranges for Total and Free Testosterone Levels

Diagnosing testosterone deficiency requires accurate and precise measurement of total testosterone levels by an accurate method, such as liquid chromatography-tandem mass spectrometry in a laboratory certified by an accuracy-based program (eg, Centers for Disease Control and Prevention's Hormone Standardization (HoST) Program), and, if needed, free testosterone level. Free testosterone level should ideally be measured by equilibrium dialysis method. Testosterone levels should be measured in 2 or more fasting samples obtained in the morning. Harmonized reference ranges for total testosterone can be applied to laboratories that certified by the HoST Program.

Associations of endogenous androgens and sex hormone-binding globulin with kidney function and chronic kidney disease

INTRODUCTION

The role of endogenous androgens in kidney function and disease has not been extensively explored in men and women.

RESEARCH DESIGN AND METHODS

We analyzed data from the observational KORA F4 study and its follow-up examination KORA FF4 (median follow-up time 6.5 years) including 1293 men and 650 peri- and postmenopausal women, not using exogenous sex hormones. We examined the associations between endogenous androgens (testosterone [T], dihydrotestosterone [DHT], free T [fT], free DHT [fDHT], and T/DHT), with estimated glomerular filtration rate (eGFR) at baseline and follow-up, prevalent, and incident chronic kidney disease (CKD) adjusting for common CKD risk factors.

RESULTS

At baseline, 73 men (5.7%) and 54 women (8.4%) had prevalent CKD. Cross-sectionally, no significant associations between androgens and kidney function were observed among men. In women, elevated T (β=-1.305, [95% CI -2.290; -0.320]) and fT (β=-1.423, [95% CI -2.449; -0.397]) were associated with lower eGFR. Prospectively, 81 men (8.8%) and 60 women (15.2%) developed incident CKD. In women, a reverse J-shaped associations was observed between DHT and incident CKD (P_non-linear=0.029), while higher fDHT was associated with lower incident CKD risk (odds ratio per 1 standard deviation=0.613, [95% CI 0.369; 0.971]. Among men, T/DHT (β=-0.819, [95% CI -1.413; -0.226]) and SHBG (P_non-linear=0.011) were associated with eGFR at follow-up but not with incident CKD. Some associations appeared to be modified by type 2 diabetes (T2D).

CONCLUSION

Suggestive associations are observed of androgens and SHBG with kidney impairment among men and women. However, larger well-phenotyped prospective studies are required to further elucidate the potential of androgens, SHBG, and T2D as modifiable risk factors for kidney function and CKD.

Homozygous SHBG Variant (rs6258) Linked to Gonadotropin-Independent Precocious Puberty in a Young Girl

Sex hormone-binding globulin (SHBG) in the blood is a major determinant of bioactivity for key sex steroids such as testosterone and estradiol. Low serum levels of SHBG have been associated with obesity, polycystic ovaries, and metabolic syndrome, and other states associated with hyperandrogenemia. A 9-year, 6-month-old girl presented with a history of peripheral precocious puberty and aggressive behavior. The patient's SHBG level was remarkably low for her age, at less than 5 nmol/L (reference range for a girl with a bone age of 10 years, 73 nmol/L [SEM = 10]) [1]. On genetic and protein analysis, the patient was found to have a homozygous missense potentially pathogenic variant in the SHBG gene (c.554C>T, p.P185L); her parents were asymptomatic heterozygote carriers. Laboratory investigations supported the possible involvement of this genetic alteration in the patient's phenotype. Various analyses of this variant support its pathogenicity, although the exact mechanism remains unclear. In conclusion, we present a genetic SHBG variant in the homozygote state that may have been associated with gonadotropin-independent precocious puberty in a young girl.

Impact of sex hormone-binding globulin on the human phenome

Background: Sex hormone-binding globulin (SHBG) is a circulating glycoprotein and a regulator of sex hormone levels, which has been shown to influence various traits and diseases. The molecular nature of SHBG makes it a feasible target for preventative or therapeutic interventions. A systematic study of its effects across the human phenome may uncover novel associations. Methods: We used a Mendelian randomization phenome-wide association study (MR-pheWAS) approach to systematically appraise the potential functions of SHBG while reducing potential biases such as confounding and reverse causation common to the literature. We searched for potential causal effects of SHBG in UK Biobank (N = 334 977) and followed-up our top findings using two-sample MR analyses to evaluate whether estimates may be biased due to horizontal pleiotropy. Results: Results of the MR-pheWAS across over 21 000 outcome phenotypes identified 12 phenotypes associated with genetically elevated SHBG after Bonferroni correction for multiple testing. Follow-up analysis using two-sample MR indicated the associations of increased natural log SHBG with higher impedance of the arms and whole body, lower pulse rate, lower bone density, higher odds of hip replacement, lower odds of high cholesterol or cholesterol medication use and higher odds of gallbladder removal. Conclusions: Our systematic MR-pheWAS of SHBG, which was comprehensive to the range of phenotypes available in UK Biobank, suggested that higher circulating SHBG affects the body impedance, bone density and cholesterol levels, among others. These phenotypes should be prioritized in future studies aiming to investigate the biological effects of SHBG or develop targets for therapeutic intervention.

Optimizing the Diagnostic Accuracy and Treatment Decisions in Men with Testosterone Deficiency

OBJECTIVE

This narrative review offers a guideline-based approach to optimizing the diagnostic evaluation and treatment decision-making in men being evaluated for testosterone deficiency.

METHODS

A narrative review RESULTS: Testosterone deficiency is a clinical syndrome that results from the inability of the testes to produce normal amounts of testosterone, and is characterized by a constellation of symptoms and signs associated with consistently low testosterone concentrations. The diagnosis of testosterone deficiency is made by ascertainment of symptoms and signs; measurement of total and, if indicated, free testosterone levels, in early morning fasting samples on 2 or more days; measurement of LH and FSH to distinguish primary from secondary hypogonadism; and additional evaluation to ascertain the cause of testosterone deficiency. Non-specificity of symptoms and signs; variations in testosterone levels over time; inaccuracy in the measurement of total and free testosterone levels; variations in binding protein concentrations; and the suboptimal reference ranges contribute to diagnostic inaccuracy. Testosterone treatment is indicated for men with symptomatic testosterone deficiency. Testosterone treatment should be avoided in men with prostate or breast cancer, erythrocytosis, thrombophilia, increased risk of prostate cancer or severe lower urinary tract symptoms without prior urological evaluation, recent major adverse cardiovascular event, uncontrolled heart failure or severe untreated sleep apnea. Testosterone replacement therapy should be accompanied by a standardized monitoring plan.

CONCLUSION

The shared decision to treat should be guided by consideration of the burden of symptoms, potential benefits and risks, patient's values, and the cost and burden of long-term treatment and monitoring.

Association of Genetically Predicted Serum Estradiol With Risk of Thromboembolism in Men: A Mendelian Randomization Study

CONTEXT

An association was recently reported between genetic markers related to high testosterone and increased risk of thromboembolism in men, but a possible causal role of estradiol for risk of thromboembolism in men remains unknown.

OBJECTIVE

This work aimed to determine whether endogenous estradiol has a causal role in thromboembolism in men.

METHODS

A 2-sample mendelian randomization study using gene-based genetic instruments assessed the association between endogenous estradiol genetically predicted by 22 variants in the aromatase CYP19A1 gene region and the risk of thromboembolism (5815 cases) in 170 593 unrelated men of White ancestry in the UK Biobank. The main outcome measure included thromboembolism based on self-reports, hospital episodes, and death.

RESULTS

Endogenous estradiol genetically predicted by variants in the CYP19A1 gene region was inversely associated with the risk of thromboembolism (odds ratio per SD increase in estradiol 0.74; 95% CI, 0.62-0.90). In contrast, genetic variants in the JMJD1C gene, used as a predictor of high endogenous testosterone, were associated with an increased risk of thromboembolism (odds ratio per SD increase in testosterone 1.39; 95% CI, 1.12-1.72). Subsequent explorative analyses evaluating potential repercussions of thromboembolism revealed that endogenous estradiol genetically predicted by variants in the CYP19A1 gene region was inversely associated with the risk of ischemic stroke (0.68; 95% CI, 0.49-0.95) but not myocardial infarction (0.97; 95% CI, 0.84-1.13).

CONCLUSION

Genetically predicted estradiol was inversely associated with the risk of thromboembolism and ischemic stroke in men. The ratio between testosterone and estradiol, determined by CYP19A1 activity, may contribute to the overall impact of sex steroids on thromboembolism in men.

Testosterone and socioeconomic position: Mendelian randomization in 306,248 men and women in UK Biobank

Men with more advantaged socioeconomic position (SEP) have been observed to have higher levels of testosterone. It is unclear whether these associations arise because testosterone has a causal impact on SEP. In 306,248 participants of UK Biobank, we performed sex-stratified genome-wide association analysis to identify genetic variants associated with testosterone. Using the identified variants, we performed Mendelian randomization analysis of the influence of testosterone on socioeconomic position, including income, employment status, neighborhood-level deprivation, and educational qualifications; on health, including self-rated health and body mass index; and on risk-taking behavior. We found little evidence that testosterone affected socioeconomic position, health, or risk-taking. Our results therefore suggest that it is unlikely that testosterone meaningfully affects these outcomes in men or women. Differences between Mendelian randomization and multivariable-adjusted estimates suggest that previously reported associations with socioeconomic position and health may be due to residual confounding or reverse causation.

[Management of chemotherapy side effects and their long-term sequelae]

Various chemotherapies are used to treat testicular cancer. The most common therapy regimens are BEP (cisplatin, etoposide, bleomycin), carboplatin mono (AUC 7), PEI (cisplatin, etoposide, ifosfamide), TIP (cisplatin, ifosfamide, paclitaxel) and GOP (gemcitabine, oxaliplatin, paclitaxel). This is accompanied by acute and late toxicities. These include general side effects such as anemia, neutropenia, nausea, vomiting, diarrhea, mucositis or paravasation as well as special toxicities like ototoxicity, nephrotoxicity, pulmonary toxicity, neurotoxicity or Raynaud's syndrome. Since young men are usually affected, the possible long-term consequences such as hypogonadism, infertility or the metabolic syndrome are very relevant. Accordingly, adequate management of the possible side effects and long-term consequences in the context of the use of chemotherapy is essential.

Genetic Susceptibility for Low Testosterone in Men and Its Implications in Biology and Screening: Data from the UK Biobank

Background

Despite strong evidence of heritability, few studies have attempted to unveil the genetic underpinnings of testosterone levels.

Objective

To identify testosterone-associated loci in a large study and assess their biological and clinical implications.

Design, setting, and participants

The participants were men from the UK Biobank. A two-stage genome-wide association study (GWAS) was first used to identify/validate loci for low testosterone (LowT, <8 nmol/l) in 80% of men (N = 148 902). The cumulative effect of independent LowT risk loci was then evaluated in the remaining 20% of men.

Outcome measurements and statistical analysis

Associations of single nucleotide polymorphisms (SNPs) with LowT were tested using an additive model. Analyses of the expression quantitative trait loci (eQTLs) were performed to assess the associations between significant SNPs and expression of nearby genes (within 1 Mbp). A genetic risk score (GRS) was used to assess the cumulative effect of multiple independent SNPs on LowT risk.

Results and limitations

The two-stage GWAS found SNPs in 141 loci of 41 cytobands that were significantly associated with LowT (p < 5 × 10^–8), including 94 novel loci from 38 cytobands. An eQTL analysis of these 141 loci revealed significant associations with RNA expression of 155 genes, including previously implicated (SHBG and JMJD1C) and novel (LIN28B, LCMT2, and ZBTB4) genes. Among the 141 loci, 42 were independently associated with LowT after a multivariable analysis. The GRS based on these 42 loci was significantly associated with LowT risk in independent individuals (N = 37 225, p_trend = 3.16 × 10^–162). The risk ratio for LowT between men in the top and those in the bottom GRS deciles was 4.98-fold. Results are limited in generalizability as only Caucasians were studied.

Conclusions

Identification of the genetic variants associated with LowT may improve our understanding of its etiology and identify high-risk men for LowT screening.

Patient summary

We identified 141 new genetic loci that can be incorporated into a genetic risk score that can potentially identify men with low testosterone.

GWAS of three molecular traits highlights core genes and pathways alongside a highly polygenic background

Genome-wide association studies (GWAS) have been used to study the genetic basis of a wide variety of complex diseases and other traits. We describe UK Biobank GWAS results for three molecular traits-urate, IGF-1, and testosterone-with better-understood biology than most other complex traits. We find that many of the most significant hits are readily interpretable. We observe huge enrichment of associations near genes involved in the relevant biosynthesis, transport, or signaling pathways. We show how GWAS data illuminate the biology of each trait, including differences in testosterone regulation between females and males. At the same time, even these molecular traits are highly polygenic, with many thousands of variants spread across the genome contributing to trait variance. In summary, for these three molecular traits we identify strong enrichment of signal in putative core gene sets, even while most of the SNP-based heritability is driven by a massively polygenic background.

Novel MicroRNA Binding Site SNPs and the Risk of Clear Cell Renal Cell Carcinoma (ccRCC): A Case-Control Study

BACKGROUND

Renal cell carcinoma represents 3% of all adult malignancies. MicroRNAs exhibit specific functions in various biological processes through their interaction with cellular mRNA involved in apoptosis and cell cycle control. Recent studies have reported the potential association of single-nucleotide polymorphisms (SNPs) in miRNA-binding sites of VHL-HIF1α pathway genes with renal cancer development and progression.

OBJECTIVE

The objective of this study is to investigate SNPs invoking an alteration in the nature of interaction with miRNA binding sites of VHL-HIF1α pathway genes.

PATIENTS & METHODS

Total 450 cases of histologically and clinically verified ccRCC and 490 controls were included in our study. Genotyping was performed using a TaqMan PCR allelic discrimination method. Kaplan-Meier method of statistical analysis was implemented to analyze the overall patient survival rate.

RESULTS

Polymorphism rs10491534 in TSC1 gene was significantly associated with risk of developing advanced ccRCC. Allele G of rs1642742 in VHL gene was significantly prevalent in ccRCC compared with control group aged 55 and older (OR = 1.5566; CI [1.1532-2.1019]). Results from the dominant model combining individuals with AG or AA genotype showed that the A allele bearers of CDCP1 rs6773576 exhibited higher risk of death compared to GG carriers (HR 3.93, 95% CI 1.76-17.21, log-rank P = 0.0033).

CONCLUSION

The present study delineated the association of miRNA binding site variants in VHL-HIF1α pathway genes with the ccRCC risk, which may affect clinical outcome.

Association Between Levels of Sex Hormones and Risk of Esophageal Adenocarcinoma and Barrett's Esophagus

BACKGROUND & AIMS

Esophageal adenocarcinoma (EAC) occurs most frequently in men. We performed a Mendelian randomization analysis to investigate whether genetic factors that regulate levels of sex hormones are associated with risk of EAC or Barrett's esophagus (BE).

METHODS

We conducted a Mendelian randomization analysis using data from patients with EAC (n = 2488) or BE (n = 3247) and control participants (n = 2127), included in international consortia of genome-wide association studies in Australia, Europe, and North America. Genetic risk scores or single-nucleotide variants were used as instrumental variables for 9 specific sex hormones. Logistic regression provided odds ratios (ORs) with 95% CIs.

RESULTS

Higher genetically predicted levels of follicle-stimulating hormones were associated with increased risks of EAC and/or BE in men (OR, 1.14 per allele increase; 95% CI, 1.01-1.27) and in women (OR, 1.28; 95% CI, 1.03-1.59). Higher predicted levels of luteinizing hormone were associated with a decreased risk of EAC in men (OR, 0.92 per SD increase; 95% CI, 0.87-0.99) and in women (OR, 0.93; 95% CI, 0.79-1.09), and decreased risks of BE (OR, 0.88; 95% CI, 0.77-0.99) and EAC and/or BE (OR, 0.89; 95% CI, 0.79-1.00) in women. We found no clear associations for other hormones studied, including sex hormone-binding globulin, dehydroepiandrosterone sulfate, testosterone, dihydrotestosterone, estradiol, progesterone, or free androgen index.

CONCLUSIONS

In a Mendelian randomization analysis of data from patients with EAC or BE, we found an association between genetically predicted levels of follicle-stimulating and luteinizing hormones and risk of BE and EAC.

Research progress on the relationship between sex hormone-binding globulin and male reproductive system diseases

Sex hormone-binding globulin, also known as testosterone-estradiol-binding globulin, is a multifunctional protein synthesised by hepatocytes. Sex hormone-binding globulin specifically binds and transports sex hormones to regulate plasma bioactive sex hormone levels and affects their bioavailability. As male sex hormone expression is dominated by testosterone, the binding of sex hormone-binding globulin with testosterone leads to the reduction in bioavailable testosterone, which cannot fulfil its physiological roles, thereby resulting in male infertility, erectile and gonadal dysfunction, prostate cancer and other male reproductive system diseases. Sex hormone-binding globulin may be involved in the pathogenesis of male reproductive system diseases, seriously affecting the quality of life of men. In this article, we review the association between sex hormone-binding globulin and male reproductive system diseases.

Effects of lifelong testosterone exposure on health and disease using Mendelian randomization

Testosterone products are prescribed to males for a variety of possible health benefits, but causal effects are unclear. Evidence from randomized trials are difficult to obtain, particularly regarding effects on long-term or rare outcomes. Mendelian randomization analyses were performed to infer phenome-wide effects of free testosterone on 461 outcomes in 161,268 males from the UK Biobank study. Lifelong increased free testosterone had beneficial effects on increased bone mineral density, and decreased body fat; adverse effects on decreased HDL, and increased risks of prostate cancer, androgenic alopecia, spinal stenosis, and hypertension; and context-dependent effects on increased hematocrit and decreased C-reactive protein. No benefit was observed for type 2 diabetes, cardiovascular or cognitive outcomes. Mendelian randomization suggests benefits of long-term increased testosterone should be considered against adverse effects, notably increased prostate cancer and hypertension. Well-powered randomized trials are needed to conclusively address risks and benefits of testosterone treatment on these outcomes.

Sex-specific genetic effects across biomarkers

Sex differences have been shown in laboratory biomarkers; however, the extent to which this is due to genetics is unknown. In this study, we infer sex-specific genetic parameters (heritability and genetic correlation) across 33 quantitative biomarker traits in 181,064 females and 156,135 males from the UK Biobank study. We apply a Bayesian Mixture Model, Sex Effects Mixture Model (SEMM), to Genome-wide Association Study summary statistics in order to (1) estimate the contributions of sex to the genetic variance of these biomarkers and (2) identify variants whose statistical association with these traits is sex-specific. We find that the genetics of most biomarker traits are shared between males and females, with the notable exception of testosterone, where we identify 119 female and 445 male-specific variants. These include protein-altering variants in steroid hormone production genes (POR, UGT2B7). Using the sex-specific variants as genetic instruments for Mendelian randomization, we find evidence for causal links between testosterone levels and height, body mass index, waist and hip circumference, and type 2 diabetes. We also show that sex-specific polygenic risk score models for testosterone outperform a combined model. Overall, these results demonstrate that while sex has a limited role in the genetics of most biomarker traits, sex plays an important role in testosterone genetics.

Hormonal regulation in male androgenetic alopecia-Sex hormones and beyond: Evidence from recent genetic studies

Male-pattern hair loss, also termed androgenetic alopecia (AGA), is a highly prevalent age-related condition that is characterized by a distinct pattern of hair loss from the frontotemporal and vertex regions of the scalp. The phenotype is highly heritable and hormone dependent, with androgens being the recognized critical hormonal factor. Numerous molecular genetic studies have focused on genetic variation in and around the gene that encodes the androgen receptor. More recently, however, the availability of high-throughput molecular genetic methods, novel methods of data analysis and sufficiently large sample sizes have rendered possible the systematic investigation of the contribution of other components of the androgen receptor pathway or hormonal pathways beyond the androgen receptor signalling pathways. Over the past decade, genome-wide association studies of increasingly large cohorts have enabled the genome-wide identification of genetic risk factors for AGA, and yielded unprecedented insights into the underlying pathobiology. The present review discusses some of the most intriguing genetic findings on the relevance of (sex)hormonal signalling in AGA.

Genome-wide association study of semen volume, sperm concentration, testis size, and plasma inhibin B levels

Semen quality is affected by environmental factors, endocrine function abnormalities, and genetic factors. A GWAS recently identified ERBB4 at 2q34 as a genetic locus associated with sperm motility. However, GWASs for human semen volume and sperm concentration have not been conducted. In addition, testis size also reportedly correlates with semen quality, and it is important to identify genes that affect testis size. Reproductive hormones also play an important role in spermatogenesis. To date, genetic loci associated with plasma testosterone, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels have been identified using GWASs. However, GWASs have not identified any relevant loci for plasma inhibin B levels. We conducted a two-stage GWAS using 811 Japanese men in a discovery stage followed by a replication stage using an additional 721 Japanese men. The results of the discovery and replication stages were combined into a meta-analysis. After setting a suggestive significance threshold for P values < 5 × 10^-6　in the discovery stage, we identified ten regions with SNPs (semen volume: one, sperm concentration: three, testes size: two, and inhibin B: four). We selected only the most significant SNP in each region for replication genotyping. Combined discovery and replication results in the meta-analysis showed that the locus 12q21.31 associated with plasma inhibin B levels (rs11116724) had the most significant association (P = 5.7 × 10^-8). The LRRIQ1 and TSPAN19 genes are located in the 12q21.31 region. This study provides new susceptibility variants that contribute to plasma inhibin B levels.

Gene mapping and genomic prediction of bull fertility using sex chromosome markers

Service sire has been recognized as an important factor affecting dairy herd fertility. Our group has reported promising results on gene mapping and genomic prediction of dairy bull fertility using autosomal SNP markers. Little is known, however, about the genetic contribution of sex chromosomes, which are enriched in genes related to sexual development and reproduction. As such, the main goal of this study was to investigate the effect of SNP markers on X and Y chromosomes (BTAX and BTAY, respectively) on sire conception rate (SCR) in US Holstein bulls. The analysis included a total of 5,014 bulls with SCR records and genotypes for roughly 291k SNP located on the autosomes, 1.5k SNP located on the pseudoautosomal region (PAR), 13.7k BTAX-specific SNP, and 24 BTAY-specific SNP. We first performed genomic scans of the sex chromosomes, and then we evaluated the genomic prediction of SCR including BTAX SNP markers in the predictive models. Two markers located on PAR and 3 markers located on the X-specific region showed significant associations with sire fertility. Interestingly, these regions harbor genes, such as FAM9B, TBL1X, and PIH1D3, that are directly implicated in testosterone concentration, spermatogenesis, and sperm motility. On the other hand, BTAY showed very low genetic variability, and none of the segregating markers were associated with SCR. Notably, model predictive ability was largely improved by including BTAX markers. Indeed, the combination of autosomal with BTAX SNP delivered predictive correlations around 0.343, representing an increase in accuracy of about 7.5% compared with the standard whole autosomal genome approach. Overall, this study provides evidence of the importance of both PAR and X-specific regions in male fertility in dairy cattle. These findings may help to improve conception rates in dairy herds through accurate genome-guided decisions on bull fertility.

Using human genetics to understand the disease impacts of testosterone in men and women

Testosterone supplementation is commonly used for its effects on sexual function, bone health and body composition, yet its effects on disease outcomes are unknown. To better understand this, we identified genetic determinants of testosterone levels and related sex hormone traits in 425,097 UK Biobank study participants. Using 2,571 genome-wide significant associations, we demonstrate that the genetic determinants of testosterone levels are substantially different between sexes and that genetically higher testosterone is harmful for metabolic diseases in women but beneficial in men. For example, a genetically determined 1 s.d. higher testosterone increases the risks of type 2 diabetes (odds ratio (OR) = 1.37 (95% confidence interval (95% CI): 1.22-1.53)) and polycystic ovary syndrome (OR = 1.51 (95% CI: 1.33-1.72)) in women, but reduces type 2 diabetes risk in men (OR = 0.86 (95% CI: 0.76-0.98)). We also show adverse effects of higher testosterone on breast and endometrial cancers in women and prostate cancer in men. Our findings provide insights into the disease impacts of testosterone and highlight the importance of sex-specific genetic analyses.

Genetic Association Study of Eight Steroid Hormones and Implications for Sexual Dimorphism of Coronary Artery Disease

CONTEXT

Steroid hormones are important regulators of physiological processes in humans and are under genetic control. A link to coronary artery disease (CAD) is supposed.

OBJECTIVE

Our main objective was to identify genetic loci influencing steroid hormone levels. As a secondary aim, we searched for causal effects of steroid hormones on CAD.

DESIGN

We conducted genome-wide meta-association studies for eight steroid hormones: cortisol, dehydroepiandrosterone sulfate (DHEAS), estradiol, and testosterone in two independent cohorts (LIFE-Adult, LIFE-Heart, maximum n = 7667), and progesterone, 17-hydroxyprogesterone, androstenedione, and aldosterone in LIFE-Heart only (maximum n = 2070). All genome-wide significant loci were tested for sex interactions. Furthermore, we tested whether previously reported CAD single-nucleotide polymorphisms were associated with our steroid hormone panel and investigated causal links between hormone levels and CAD status using Mendelian randomization (MR) approaches.

RESULTS

We discovered 15 novel associated loci for 17-hydroxyprogesterone, progesterone, DHEAS, cortisol, androstenedione, and estradiol. Five of these loci relate to genes directly involved in steroid metabolism, that is, CYP21A1, CYP11B1, CYP17A1, STS, and HSD17B12, almost completing the set of steroidogenic enzymes with genetic associations. Sexual dimorphisms were found for seven of the novel loci. Other loci correspond, for example, to the WNT4/β-catenin pathway. MR revealed that cortisol, androstenedione, 17-hydroxyprogesterone, and DHEA-S had causal effects on CAD. We also observed enrichment of cortisol and testosterone associations among known CAD hits.

CONCLUSION

Our study greatly improves insight into genetic regulation of steroid hormones and their dependency on sex. These results could serve as a basis for analyzing sexual dimorphism in other complex diseases.

The genetic architecture of osteoporosis and fracture risk

Osteoporosis and fracture risk are common complex diseases, caused by an interaction of numerous disease susceptibility genes and environmental factors. With the advances in genomic technologies, large-scale genome-wide association studies (GWAS) have been performed which have broadened our understanding of the genetic architecture and biological mechanisms of complex disease. Currently, more than ~90 loci have been found associated with DXA derived bone mineral density (BMD), over ~500 loci with heel estimated BMD and several others with other less widely available bone parameters such as bone geometry, shape, and microarchitecture. Notably, several of the pathways identified by the GWAS efforts correspond to pathways that are currently targeted for the treatment of osteoporosis. Overall, tremendous progress in the field of the genetics of osteoporosis has been achieved with the discovery of WNT16, EN1, DAAM2, and GPC6 among others. Assessment of the function and biological mechanisms of the remaining genes may further untangle the complex genetic landscape of osteoporosis and fracture risk. With this review we aimed to provide a general overview of the existing GWAS studies on osteoporosis traits and fracture risk.

Unraveling the functional role of the orphan solute carrier, SLC22A24 in the transport of steroid conjugates through metabolomic and genome-wide association studies

Variation in steroid hormone levels has wide implications for health and disease. The genes encoding the proteins involved in steroid disposition represent key determinants of interindividual variation in steroid levels and ultimately, their effects. Beginning with metabolomic data from genome-wide association studies (GWAS), we observed that genetic variants in the orphan transporter, SLC22A24 were significantly associated with levels of androsterone glucuronide and etiocholanolone glucuronide (sentinel SNPs p-value <1x10-30). In cells over-expressing human or various mammalian orthologs of SLC22A24, we showed that steroid conjugates and bile acids were substrates of the transporter. Phylogenetic, genomic, and transcriptomic analyses suggested that SLC22A24 has a specialized role in the kidney and appears to function in the reabsorption of organic anions, and in particular, anionic steroids. Phenome-wide analysis showed that functional variants of SLC22A24 are associated with human disease such as cardiovascular diseases and acne, which have been linked to dysregulated steroid metabolism. Collectively, these functional genomic studies reveal a previously uncharacterized protein involved in steroid homeostasis, opening up new possibilities for SLC22A24 as a pharmacological target for regulating steroid levels.

Aging and the Male Reproductive System

This narrative review presents an overview of current knowledge on fertility and reproductive hormone changes in aging men, the factors driving and modulating these changes, their clinical consequences, and the benefits and risks of testosterone (T) therapy. Aging is accompanied by moderate decline of gamete quality and fertility. Population mean levels show a mild total T decline, an SHBG increase, a steeper free T decline, and a moderate LH increase with important contribution of comorbidities (e.g., obesity) to these changes. Sexual symptoms and lower hematocrit are associated with low T and are partly responsive to T therapy. The relationship of serum T with body composition and metabolic health is bidirectional; limited beneficial effects of T therapy on body composition have only marginal effects on metabolic health and physical function. Skeletal changes are associated primarily with estradiol and SHBG. Cognitive decline is not consistently linked to low T and is not improved by T therapy. Although limited evidence links moderate androgen decline with depressive symptoms, T therapy has small beneficial effects on mood, depressive symptoms, and vitality in elderly patients with low T. Suboptimal T (and/or DHT) has been associated with increased risk of stroke, but not of ischemic heart disease, whereas an association with mortality probably reflects that low T is a marker of poor health. Globally, neither severity of clinical consequences attributable to low T nor the nature and magnitude of beneficial treatment effects justify the concept of some broadly applied "T replacement therapy" in older men with low T. Moreover, long-term safety of T therapy is not established.

Effects of SHBG rs1799941 Polymorphism on Free Testosterone Levels and Hypogonadism Risk in Young Non-Diabetic Obese Males

Introduction: Obesity has been associated with increased risk of presenting hypogonadism. Free testosterone (FT) is the fraction of testosterone that carries out the biological function of testosterone, and is determined from total testosterone (TT) and sex-hormone binding globulin (SHBG) levels. We aimed to study the SHBG polymorphism rs1799941 in a cohort of young non-diabetic obese males to unravel the possible implication of this polymorphism in obesity-related hypogonadism. Methodology: 212 young (<45 years) non-diabetic obese (BMI ≥ 30 kg/m²) males participated in this study. Subjects were classified according to TT and FT levels in: Eugonadal (n = 55, TT > 3.5 ng/mL and FT ≥ 70 pg/mL; EuG), normal FT hypogonadism (n = 40, TT < 3.5 and FT ≥ 70 pg/mL; normal FT HG) and hypogonadism (n = 117, TT < 3.5 ng/mL and TL < 70 pg/mL; HG). The SHBG rs1799941 polymorphism (GG/GA/AA) was analyzed using the Taqman Open Array (Applied biosystem). Results: The rs1799941 frequencies were different among the groups. Higher proportion of the allele (A) was found in HG, compared to EuG and normal FT HG. Among the genotypes, the rare homozygous (AA) were found in the normal FT HG group and higher levels of serum SHBG and lower of FT were observed. The presence of the allele A was related (according to lineal regression models) to an increased of SHBG levels ((GA) β = 3.28; (AA) β = 12.45) and a decreased of FT levels ((GA) β = −9.19; (AA) β = −18.52). The presence of the allele (A) increased the risk of presenting HG compared to normal FT HG (OR = 2.54). Conclusions: The rs1799941 of the SHBG gene can partially determine the presence of obesity-related hypogonadism in young non-diabetic males and whether these subjects have normal FT HG.

Contribution of Liver Fat to Weight Loss-Induced Changes in Serum Hepatokines: A Randomized Controlled Trial

CONTEXT

Hepatokines have emerged as potential mediators of obesity-associated comorbidities, such as type 2 diabetes, cardiovascular disease, fractures, and central hypogonadism.

OBJECTIVE

To assess whether weight loss-induced changes in hepatokines are mediated by intrahepatic triglyceride (IHTG) content.

DESIGN

Cross-sectional study and randomized controlled trial.

SETTING

General community.

PARTICIPANTS

Metabolically healthy, lean men (waist <94 cm; n = 25) and men with abdominal obesity (waist 102 to 110 cm; n = 52).

INTERVENTION

Men with abdominal obesity were randomized to 8-week dietary weight loss or no weight loss.

MAIN OUTCOME MEASURES

IHTG and serum hepatokines, that is, serum IGF1, IGF binding protein 1 (IGFBP1), SHBG, fibroblast growth factor 21 (FGF21), fetuin A, and plasma fetuin B.

RESULTS

All hepatokines, except for fetuin B, were significantly different between lean men and men with obesity. After the weight-loss intervention (-10.3 kg; 95% CI, -11.4 to-9.2), serum IGF1, IGFBP1, SHBG, and fetuin A approached the values observed in lean men. Cross-sectional associations were observed between IHTG and IGF1 (β = -0.51; 95% CI, -0.82 to -0.20), IGFBP1 (β = -4.2; 95% CI, -7.7 to -0.7), and FGF21 (β = 2.1; 95% CI, 1.3 to 2.9) in lean men and men with abdominal obesity combined. Weight loss resulted in a reduction of IHTG (treatment effect, -2.2%; 95% CI, -3.4% to -1.2%) that was associated with a change in IGF1 (β = -0.9; 95% CI, -1.3 to -0.4), IGFBP1 (β = -0.17; 95% CI, -0.31 to -0.03), and SHBG levels (β = -0.18; 95% CI, -0.29 to -0.07). Mediation analyses showed that only the weight loss-induced change in serum IGF1 was mediated by IHTG (mediated effect, 32.7%; 95% CI, 4.6% to 79.2%).

CONCLUSIONS

Dietary weight loss has differential effects on hepatokines. This study shows that the change in serum IGF1 levels after dietary weight loss is mediated by the change in IHTG content.

Genetic and observational evidence supports a causal role of sex hormones on the development of asthma

INTRODUCTION

Males have a higher prevalence of asthma in childhood, whereas females have a higher prevalence in adolescence and adulthood. The 'adolescent switch' observed between sexes during puberty has been hypothesised to be due to fluctuating sex hormones. Robust evidence of the involvement of sex hormones in asthma could lead to development of therapeutic interventions.

METHODS

We combine observational evidence using longitudinal data on sex hormone-binding globulin (SHBG), total and bioavailable testosterone and asthma from a subset of males (n=512) in the Avon Longitudinal Study of Parents and Children, and genetic evidence of SHBG and asthma using two-sample Mendelian randomisation (MR), a method of causal inference. We meta-analysed two-sample MR results across two large data sets, the Trans-National Asthma Genetics Consortium genome-wide association study of asthma and UK Biobank (over 460 000 individuals combined).

RESULTS

Observational evidence indicated weak evidence of a protective effect of increased circulating testosterone on asthma in males in adolescence, but no strong pattern of association with SHBG. Genetic evidence using two-sample MR indicated a protective effect of increased SHBG, with an OR for asthma of 0.86 (95% CI 0.74 to 1.00) for the inverse-variance weighted approach and an OR of 0.83 (95% CI 0.72 to 0.96) for the weighted median estimator, per unit increase in natural log SHBG. A sex-stratified sensitivity analysis suggested the protective effect of SHBG was mostly evident in females.

CONCLUSION

We report the first suggestive evidence of a protective effect of genetically elevated SHBG on asthma, which may provide a biological explanation behind the observed asthma sex discordance. Further work is required to disentangle the downstream effects of SHBG on asthma and the molecular pathways involved.

Sex hormone binding globulin and risk of breast cancer: a Mendelian randomization study

BACKGROUND

There are observational data suggesting an inverse association between circulating concentrations of sex hormone binding globulin (SHBG) and risk of postmenopausal breast cancer. However, causality is uncertain and few studies have investigated this association by tumour receptor status. We aimed to investigate these associations under the causal framework of Mendelian randomization (MR).

METHODS

We used summary association estimates extracted from published genome-wide association study (GWAS) meta-analyses for SHBG and breast cancer, to perform two-sample MR analyses. Summary statistics were available for 122 977 overall breast cancer cases, of which 69 501 were estrogen receptor positive (ER+ve) and 21 468 were ER-ve, and 105 974 controls. To control for potential horizontal pleiotropy acting via body mass index (BMI), we performed multivariable inverse-variance weighted (IVW) MR as the main analysis, with the robustness of this approach further tested in sensitivity analyses.

RESULTS

The multivariable IVW MR analysis indicated a lower risk of overall (odds ratio [OR]: 0.94; 95% confidence interval [CI]: 0.90, 0.98; P: 0.006) and ER+ve (OR: 0.92; 95% CI: 0.87, 0.97; P: 0.003) breast cancer, and a higher risk of ER-ve disease (OR: 1.09; 95% CI: 1.00, 1.18; P: 0.047) per 25 nmol/L higher SHBG levels. Sensitivity analyses were consistent with the findings of the main analysis.

CONCLUSIONS

We corroborated the previous literature evidence coming from observational studies for a potentially causal inverse association between SHBG concentrations and risk of ER+ve breast cancer, but our findings also suggested a potential novel positive association with ER-ve disease that warrants further investigation, given the low prior probability of being true.

Genetic polymorphisms of the SHBG gene can be the effect on SHBG and HDL-cholesterol levels in Coronary Heart Disease: a case-control study

Sex hormone binding globulin (SHBG) level is positively associated with the high-density lipoprotein cholesterol (HDL-C) levels. The aim of this study was to investigate the effects of the SHBG gene variations (D356N, rs1799941, and P156L) on SHBG and HDL-C levels and Coronary Heart Disease (CHD) risk. The SHBG D356 N (rs6259,G > A), P156L (rs6258,C > T), and rs1799941(G > A) polymorphisms were determined in 131 male CHD patients and 55 male controls by PCR-RFLP and real-time PCR techniques. SHGB levels were measured by Electro-chemiluminescence immunoassay (ECLIA). In the patients who had SHBG levels lower than threshold 35 nmol/l value, the risk of being HDL-C levels lower than threshold 0.90 mmol/l value was observed statistically significant (p = 0.017; OR 2.522, 95% CI 1.170-5.438). The rs1799941 GG was associated with increased CHD risk when compared with the A allele carriers (GA + AA) (p = 0.019, OR 2.222, 95% CI 1.130-4.371). In addition, the rs1799941 GG genotype and D356 N N allele were associated with lower SHBG in the CHD group (p < 0.01). The logistic regression analysis also revealed the rs1799941 GG genotype was significantly associated with low SHBG in CHD patients. It was observed that Haplotype-1(rs1799941 G allele-P156L P allele-D356 N D allele) was associated with increased CHD risk, while Haplotype-2 (rs1799941 rare A allele-P156L C allele- D356 N G allele) was correlated with the decreased CHD risk (p = 0.0167). Our findings suggest that there is a positive correlation between SHBG and HDL-C levels in CHD patients, and this association might be affected by SHBG gene variations.

Pharmacokinetics of the 1.5 mg levonorgestrel emergency contraceptive in women with normal, obese and extremely obese body mass index

OBJECTIVE

To assess the pharmacokinetics (PK) of levonorgestrel after 1.5 mg oral doses (LNG-EC) in women with normal, obese and extremely obese body mass index (BMI).

STUDY DESIGN

The 1.5 mg LNG dose was given to healthy, reproductive-age, ovulatory women with normal BMI (mean 22.0), obese (mean 34.4), and extremely obese (mean 46.6 kg/m2) BMI. Total serum LNG was measured over 0 to 96 h by radioimmunoassay while free and bioavailable LNG were calculated. The maximum concentration (Cmax), time to maximum concentration (Tmax), and area under the curve (AUC) of LNG were assessed. Pharmacokinetic parameters calculated included half-life (t1/2), clearance (CL) and volume of distribution (Vss).

RESULTS

Ten normal-BMI, 11 obese-BMI, 5 extremely obese-BMI women were studied. After LNG-EC, mean total LNG metrics were lower in the obese and extremely obese groups compared to normal (Cmax 10.5 and 10.5 versus 16.2 ng/mL, both p<.01; AUC 208 and 197 versus 360 h × ng/mL, both p<.05). Mean bioavailable LNG Cmax was lower in obese (7.03 ng/mL, p<.05) and extremely obese (7.53 ng/ml, p=.198) compared to normal BMI (9.39 ng/mL). Mean bioavailable LNG AUC values were lower in obese and extremely obese compared to normal (131.6 and 127.5 vs 185.0 h × ng/mL, p<.05 for both).

CONCLUSIONS

Obese and extremely obese women were exposed to lower total and bioavailable LNG than normal BMI women.

IMPLICATIONS

Lower 'bioavailable' (free plus albumin bound) LNG AUC in obese women may play a role in the purported reduced efficacy of LNG-EC in obese users.