Insulin-like peptide 3 (INSL3) as an indicator of leydig cell insufficiency (LCI) in Middle-aged and older men with hypogonadism: reference range and threshold

Insulin-like peptide 3 (INSL3) is a circulating biomarker for Leydig cell functional capacity in men, also indicating Leydig Cell Insufficiency (LCI) and potential primary hypogonadism. Using results from large cohort studies we explore sources of biological and technical variance, and establish a reference range for adult men. It is constitutively secreted with little within-individual variation and reflects testicular capacity to produce testosterone. The main INSL3 assays available indicate good concordance with low technical variance; there is no effect of ethnicity. INSL3 declines with age from 35 years at about 15% per decade. Like low calculated free testosterone, and to a lesser extent low total testosterone, reduced INSL3 is significantly associated with increasing age-related morbidity, including lower overall sexual function, reflecting LCI. Consequently, low INSL3 (≤0.4 ng/ml; ca. 35 years) reference range (serum) for INSL3 in the eugonadal population of 0.4 − 2.3 ng/ml, with low INSL3 prospectively identifying individuals at risk of increased future morbidity

Association of age, hormonal, and lifestyle factors with the Leydig cell biomarker INSL3 in aging men from the European Male Aging Study cohort

Background: Aging in men is accompanied by a broad range of symptoms, including sexual dysfunction, cognitive and musculoskeletal decline, obesity, type 2 diabetes, cardiovascular disease and hypertension, organ degeneration/failure, and increasing neoplasia, some of which are associated with declining levels of Leydig cell-produced testosterone. High natural biological variance, together with multiple factors that can modulate circulating testosterone concentration, may influence its interpretation and clinical implications. Insulin-like peptide 3 is a biomarker of Leydig cell function that might provide complementary information on testicular health and its downstream outcomes. Objectives: To characterize insulin-like peptide 3 as a biomarker to assess gonadal status in aging men. Methods and materials: A large European multicenter (European Male Aging Study) cohort of community-dwelling men was analyzed to determine how insulin-like peptide 3 relates to a range of hormonal, anthropometric, and lifestyle parameters. Results and discussion: Insulin-like peptide 3 declines cross-sectionally and longitudinally within individuals at approximately 15% per decade from age 40 years, unlike testosterone (1.9% per decade), which is partly compensated by increasing pituitary luteinizing hormone production. Importantly, lower insulin-like peptide 3 in younger men appears to persist with aging. Multiple regression analysis shows that, unlike testosterone, insulin-like peptide 3 is negatively dependent on luteinizing hormone and sex hormone-binding globulin and positively dependent on follicle-stimulating hormone, suggesting a different mechanism of gonadotropic regulation. Circulating insulin-like peptide 3 is negatively associated with increased body mass index or waist circumference and with smoking, and unlike testosterone, it is not affected by weight loss in obese individuals. Geographic variation in mean insulin-like peptide 3 within Europe appears to be largely explained by differences in these parameters. The results allowed the establishment of a European-wide reference range for insulin-like peptide 3 (95% confidence interval) adjusted for increasing age. Conclusion: Insulin-like peptide 3 is a constitutive biomarker of Leydig cell functional capacity and is a robust, reliably measurable peptide not subject to gonadotropin-dependent short-term regulation and within-individual variation in testosterone

Genetic Determinants of Circulating Estrogen Levels and Evidence of a Causal Effect of Estradiol on Bone Density in Men.

CONTEXT: Serum estradiol (E2) and estrone (E1) levels exhibit substantial heritability. OBJECTIVE: To investigate the genetic regulation of serum E2 and E1 in men. DESIGN, SETTING, AND PARTICIPANTS: Genome-wide association study in 11,097 men of European origin from nine epidemiological cohorts. MAIN OUTCOME MEASURES: Genetic determinants of serum E2 and E1 levels. RESULTS: Variants in/near CYP19A1 demonstrated the strongest evidence for association with E2, resolving to three independent signals. Two additional independent signals were found on the X chromosome; FAMily with sequence similarity 9, member B (FAM9B), rs5934505 (P = 3.4 × 10-8) and Xq27.3, rs5951794 (P = 3.1 × 10-10). E1 signals were found in CYP19A1 (rs2899472, P = 5.5 × 10-23), in Tripartite motif containing 4 (TRIM4; rs17277546, P = 5.8 × 10-14), and CYP11B1/B2 (rs10093796, P = 1.2 × 10-8). E2 signals in CYP19A1 and FAM9B were associated with bone mineral density (BMD). Mendelian randomization analysis suggested a causal effect of serum E2 on BMD in men. A 1 pg/mL genetically increased E2 was associated with a 0.048 standard deviation increase in lumbar spine BMD (P = 2.8 × 10-12). In men and women combined, CYP19A1 alleles associated with higher E2 levels were associated with lower degrees of insulin resistance. CONCLUSIONS: Our findings confirm that CYP19A1 is an important genetic regulator of E2 and E1 levels and strengthen the causal importance of E2 for bone health in men. We also report two independent loci on the X-chromosome for E2, and one locus each in TRIM4 and CYP11B1/B2, for E1

Frailty and bone health in European men

© The Author 2017. Published by Oxford University Press on behalf of the British Geriatrics Society.All rights reserved. Background: frailty is associated with an increased risk of fragility fractures. Less is known, however, about the association between frailty and bone health.Methods: men aged 40-79 years were recruited from population registers in eight European centres for participation in the European Male Aging Study. Subjects completed a comprehensive assessment which included quantitative ultrasound (QUS) scan of the heel (Hologic-SAHARA) and in two centres, dual-energy bone densitometry (dual-energy x-ray absorptiometry, DXA). Frailty was defined based on an adaptation of Fried's phenotype criteria and a frailty index (FI) was constructed. The association between frailty and the QUS and DXA parameters was determined using linear regression, with adjustments for age, body mass index and centre.Results: in total, 3,231 subjects contributed data to the analysis. Using the Fried categorisation of frailty, pre-frail and frail men had significantly lower speed of sound (SOS), broadband ultrasound attenuation (BUA) and quantitative ultrasound index (QUI) compared to robust men (P 0.35) was associated with lower lumbar spine BMD (P < 0.05) when compared to those with low (FI < 0.2), but not lower femoral neck BMD. When analysed as a continuous variable, higher FI was linked with lower SOS, BUA and QUI (P < 0.05).Conclusions: optimisation of bone health as well as prevention of falls should be considered as strategies to reduce fractures in frail older people

Identifying a Window of Vulnerability during Fetal Development in a Maternal Iron Restriction Model

It is well acknowledged from observations in humans that iron deficiency during pregnancy can be associated with a number of developmental problems in the newborn and developing child. Due to the obvious limitations of human studies, the stage during gestation at which maternal iron deficiency causes an apparent impairment in the offspring remains elusive. In order to begin to understand the time window(s) during pregnancy that is/are especially susceptible to suboptimal iron levels, which may result in negative effects on the development of the fetus, we developed a rat model in which we were able to manipulate and monitor the dietary iron intake during specific stages of pregnancy and analyzed the developing fetuses. We established four different dietary-feeding protocols that were designed to render the fetuses iron deficient at different gestational stages. Based on a functional analysis that employed Auditory Brainstem Response measurements, we found that maternal iron restriction initiated prior to conception and during the first trimester were associated with profound changes in the developing fetus compared to iron restriction initiated later in pregnancy. We also showed that the presence of iron deficiency anemia, low body weight, and changes in core body temperature were not defining factors in the establishment of neural impairment in the rodent offspring

Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Sociodemographic, lifestyle and medical influences on serum testosterone and sex hormone-binding globulin in men from UK Biobank

OBJECTIVE: Serum testosterone concentrations are affected by factors unrelated to hypothalamo-pituitary-testicular axis pathology. We evaluated the impact of sociodemographic, lifestyle and medical factors, on serum testosterone and sex hormone-binding globulin (SHBG) in men aged 40-69 years. DESIGN: Cross-sectional analysis of 208,677 community-dwelling men from the UK Biobank. MEASUREMENTS: We analysed associations of different factors with serum testosterone and SHBG (immunoassays) and calculated free testosterone (cFT), using smoothed centile plots, linear mixed models and effect size estimates. RESULTS: Median (interquartile range) for serum testosterone was 11.6 (9.4-14.1) nmol/L, SHBG 36.9 (27.9-48.1) nmol/L and cFT 213 (178-255) pmol/L. Age and BMI were inversely associated with testosterone and cFT, while SHBG was associated with age and inversely with BMI (all P < .001). Living with a partner, (South) Asian ethnicity, never or previous smoker and some medical conditions were associated with lower testosterone. Poultry or fish eater, and higher physical activity were associated with higher testosterone (all P < .001). Testosterone was lowered by ~0.5 nmol/L across ages, ~1.5 nmol/L for BMI 30 vs 25 kg/m2 , ~2 nmol/L for (South) Asian ethnicity, living with partner, college/university qualifications, low red meat eater, insufficient physical activity and 0.3-1.0 nmol/L with cardiovascular disease or diabetes. Different combinations of these factors varied serum testosterone by ~4 nmol/L, SHBG by ~30 nmol/L and cFT by ~60 pmol/L. CONCLUSIONS: The identified modifiable risk factors support lifestyle-based interventions in men with low testosterone concentrations. Considering sociodemographic, lifestyle and medical factors facilitates more personalized interpretation of testosterone testing results with respect to existing reference ranges.status: publishe

Nonandrogenic Anabolic Hormones Predict Risk of Frailty: European Male Ageing Study Prospective Data

Context: Low levels of nonandrogenic anabolic hormones have been linked with frailty, but evidence is conflicting and prospective data are largely lacking. Objective: To determine associations between nonandrogenic anabolic hormones and prospective changes in frailty status. Design/Setting: A 4.3-year prospective observational study of community-dwelling men participating in the European Male Ageing Study. Participants: Men (n = 3369) aged 40 to 79 years from eight European centers. Main Outcome Measures: Frailty status was determined using frailty phenotype (FP; n = 2114) and frailty index (FI; n = 2444). Analysis: Regression models assessed relationships between baseline levels of insulinlike growth factor 1 (IGF-1), its binding protein 3 (IGFBP-3), dehydroepiandrosterone sulfate (DHEA-S), 25-hydroxyvitamin D (25OHD), and parathyroid hormone (PTH), with changes in frailty status (worsening or improving frailty). Results: The risk of worsening FP and FI decreased with 1 standard deviation higher IGF-1, IGFBP-3, and 25OHD in models adjusted for age, body mass index, center, and baseline frailty [IGF-1: odds ratio (OR) for worsening FP, 0.82 (0.73, 0.93), percentage change in FI, -3.7% (-6.0, -1.5); IGFBP-3: 0.84 (0.75, 0.95), -4.2% (-6.4, -2.0); 25OHD: 0.84 (0.75, 0.95); -4.4%, (-6.7, -2.0)]. Relationships between IGF-1 and FI were attenuated after adjusting for IGFBP-3. Higher DHEA-S was associated with a lower risk of worsening FP only in men >70 years old [OR, 0.57 (0.35, 0.92)]. PTH was unrelated to change in frailty status. Conclusions: These longitudinal data confirm the associations between nonandrogenic anabolic hormones and the changes in frailty status. Interventional studies are needed to establish causality and determine therapeutic implications.status: publishe

Symptomatic androgen deficiency develops only when both total and free testosterone decline in obese men who may have incident biochemical secondary hypogonadism: Prospective results from the EMAS

OBJECTIVE: Limited evidence supports the use of free testosterone (FT) for diagnosing hypogonadism when sex hormone-binding globulin (SHBG) is altered. Low total testosterone (TT) is commonly encountered in obesity where SHBG is typically decreased. We aimed to assess the contribution of FT in improving the diagnosis of symptomatic secondary hypogonadism (SH), identified initially by low total testosterone (TT), and then further differentiated by normal FT (LNSH) or low FT (LLSH). DESIGN: Prospective observational study with a median follow-up of 4.3 years. PATIENTS: Three thousand three hundred sixty-nine community-dwelling men aged 40-79 years from eight European centres. MEASUREMENTS: Subjects were categorized according to baseline and follow-up biochemical status into persistent eugonadal (referent group; n = 1880), incident LNSH (eugonadism to LNSH; n = 101) and incident LLSH (eugonadism to LLSH; n = 38). Predictors and clinical features associated with the transition from eugonadism to LNSH or LLSH were assessed. RESULTS: The cumulative incidence of LNSH and LLSH over 4.3 years was 4.9% and 1.9%, respectively. Baseline obesity predicted both LNSH and LLSH, but the former occurred more frequently in younger men. LLSH, but not LNSH, was associated with new/worsened sexual symptoms, including low desire [OR = 2.67 (1.27-5.60)], erectile dysfunction [OR = 4.53 (2.05-10.01)] and infrequent morning erections [OR = 3.40 (1.48-7.84)]. CONCLUSIONS: These longitudinal data demonstrate the importance of FT in the diagnosis of hypogonadism in obese men with low TT and SHBG. The concurrent fall in TT and FT identifies the minority (27.3%) of men with hypogonadal symptoms, which were not present in the majority developing low TT with normal FT.status: publishe