Ethnic differences in male reproductive hormones and relationships with adiposity and insulin resistance in older men

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. <2 SD from the population mean) might serve as an additional biochemical marker in the assessment of functional hypogonadism (late-onset hypogonadism, LOH) where testosterone is in the borderline low range. Excluding individuals with low LCI (INSL3 ≤ 0.4 ng/ml) leads to an age-independent (> 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.

Different correlation of body mass index with body fatness and obesity-related biomarker according to age, sex and race-ethnicity

The relationship between body mass index (BMI) and body fatness could differ according to age, sex, and race-ethnicity. We aimed to evaluate in which contexts BMI could be a good measure for body fatness compared to dual-energy X-ray absorptiometry (DXA) derived measures. The study population included 18,061 participants (9141 men and 8920 women) aged 18 and older who tested DXA from the National Health and Nutrition Examination Survey (NHANES) database from 1999 to 2006, and 8107 men and 10,754 women with DXA data from Korea NHANES from 2008 to 2011 to represent the Asian population. We calculated Pearson correlation coefficients between BMI and DXA derived fat mass index (FMI) and percentage body fat (PBF) depending on age, sex, and race-ethnicity. The correlation between BMI, FMI and PBF and obesity-related biomarkers was also estimated among the subgroup with both DXA and information on each biomarker. BMI was strongly correlated with FMI (r = 0.944 in men and 0.976 in women), PBF (r = 0.735 in men and 0.799 in women), and truncal fat mass (r = 0.914 in men and 0.941 in women) with correlations stronger in women than in men except for with waist-height ratio (r = 0.921 in men and 0.911 in women). The correlation between BMI and DXA derived adiposity weakened with age in both sexes. BMI was less correlated with FMI (r = 0.840 in men and 0.912 in women), PBF (r = 0.645 in men and 0.681 in women), and truncal fat mass (r = 0.836 in men and 0.884 in women) in Korean compared to other race-ethnicities. Among obesity-related biomarkers, insulin was the most strongly correlated to body adiposity indices in both sexes and strength of these correlations generally decreased with age. BMI predicted obesity-related biomarkers as well as FMI and truncal fat mass and superior to PBF. BMI could be a good measure for body fatness, particularly among young age groups, women, the US population, but less so in Korean populations. The lower correlation between BMI and body fatness in older compared to younger age groups could be related to increasing PBF and decreasing lean body mass.

Ethnic inequalities in multiple long-term health conditions in the United Kingdom: a systematic review and narrative synthesis

Indicative evidence suggests that minoritised ethnic groups have higher risk of developing multiple long-term conditions (MLTCs), and do so earlier than the majority white population. While there is evidence on ethnic inequalities in single health conditions and comorbidities, no review has attempted to look across these from a MLTCs perspective. As such, we currently have an incomplete understanding of the extent of ethnic inequalities in the prevalence of MLTCs. Further, concerns have been raised about variations in the way ethnicity is operationalised and how this impedes our understanding of health inequalities. In this systematic review we aimed to 1) describe the literature that provides evidence of ethnicity and prevalence of MLTCs amongst people living in the UK, 2) summarise the prevalence estimates of MLTCs across ethnic groups and 3) to assess the ways in which ethnicity is conceptualised and operationalised. We focus on the state of the evidence prior to, and during the very early stages of the pandemic. We registered the protocol on PROSPERO (CRD42020218061). Between October and December 2020, we searched ASSIA, Cochrane Library, EMBASE, MEDLINE, PsycINFO, PubMed, ScienceDirect, Scopus, Web of Science, OpenGrey, and reference lists of key studies/reviews. The main outcome was prevalence estimates for MLTCs for at least one minoritised ethnic group, compared to the majority white population. We included studies conducted in the UK reporting on ethnicity and prevalence of MLTCs. To summarise the prevalence estimates of MLTCs across ethnic groups we included only studies of MLTCs that provided estimates adjusted at least for age. Two reviewers screened and extracted data from a random sample of studies (10%). Data were synthesised using narrative synthesis. Of the 7949 studies identified, 84 met criteria for inclusion. Of these, seven contributed to the evidence of ethnic inequalities in MLTCs. Five of the seven studies point to higher prevalence of MLTCs in at least one minoritised ethnic group compared to their white counterparts. Because the number/types of health conditions varied between studies and some ethnic populations were aggregated or omitted, the findings may not accurately reflect the true level of ethnic inequality. Future research should consider key explanatory factors, including those at the macrolevel (e.g. racism, discrimination), as they may play a role in the development and severity of MLTCs in different ethnic groups. Research is also needed to ascertain the extent to which the COVID19 pandemic has exacerbated these inequalities.

Contribution of serum anti-Müllerian hormone in the management of azoospermia and the prediction of testicular sperm retrieval outcomes: a study of 155 adult men

Background

Testicular sperm extraction (TESE) is the method of choice for recovering spermatozoa in patients with azoospermia. However, the lack of reliable biomarkers makes it impossible to predict sperm retrieval outcomes at TESE. To date, little attention has been given to anti-Müllerian hormone (AMH) serum levels in adult men with altered spermatogenesis. In this study we aimed to investigate whether serum concentrations of AMH and the AMH to total testosterone ratio (AMH/T) might be predictive factors for sperm retrieval outcomes during TESE in a cohort of 155 adult Caucasian men with azoospermia.

Results

AMH serum levels were significantly lower in nonobstructive azoospermia (NOA) that was unexplained, cryptorchidism-related, cytotoxic and genetic (medians [pmol/l] = 30.1; 21.8; 26.7; 7.3; and p = 0.02; 0.001; 0.04; <0.0001, respectively]) compared with obstructive azoospermia (OA) (median = 44.8 pmol/l). Lowest values were observed in cases of genetic NOA (p < 0.0001, compared with unexplained NOA) and especially in individuals with non-mosaic Klinefelter syndrome (median = 2.3 pmol/l, p <0.0001). Medians of AMH/T values were significantly lower in genetic NOA compared to unexplained, cryptorchidism-related NOA as well as OA. Only serum concentrations of AMH differed significantly between positive and negative groups in men with non-mosaic Klinefelter syndrome. The optimal cut-off of serum AMH was set at 2.5 pmol/l. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of this cut-off to predict negative outcomes of SR were 100 %, 76.9 %, 66.6 %, 100 and 84.2 %, respectively.

Conclusions

Serum AMH levels, but not AMH/T values, are a good marker for Sertoli and germ cell population dysfunction in adult Caucasian men with non-mosaic Klinefelter syndrome and could help us to predict negative outcomes of SR at TESE with 100 % sensitivity when serum levels of AMH are below 2.5 pmol/l.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12610-021-00133-9.

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.

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.

Long-term safety, health and mental status in men with vasectomy

Vasectomy is an efficient male contraceptive method, but the long-term effects of this technology in a large population are unclear. To investigate the influence of vasectomy on long-term health effects, we recruited 485 men with a vasectomy and 1940 men without vasectomy in China. After obtaining basic information from the Aging Males’ Symptoms (AMS) scale and other questionnaires, peripheral blood was drawn to assess the hormone levels, prostate specific antigen (PSA) and blood biochemistry. Using multiple linear regression analysis, these factors had no relationship with vasectomy except for four factors including the Somatic score (0.31, 0.02 and 0.61) in AMS, SF-36 score (−18.8, −32.00 and −5.60), “Role emotional” (−6.28, −10.34 and −2.22) and “Mental health” (−1.55, −3.08 and −0.02). A stratified analysis showed that with increased age, smoking and drinking, residence in township or a higher level of education, the mental health of men was worse. Vasectomy had no long-term effect on the level of sexual hormones in men, and it did not increase the level of PSA. The impact of the vasectomy on quality of life in men were mainly reflected in psychological effects, which suggests that men with vasectomy groups many benefit from professional psychological counseling.

Progressive impairment of testicular endocrine function in ageing men: Testosterone and dihydrotestosterone decrease, and luteinizing hormone increases, in men transitioning from the 8th to 9th decades of life

CONTEXT

Sex hormone trajectories in ageing men and their health implications remain unclear. We examined longitudinal trajectories and associations of testosterone (T), dihydrotestosterone (DHT), oestradiol (E2), luteinizing hormone (LH) and sex hormone-binding globulin (SHBG) in oldest old men.

DESIGN

Prospective cohort study.

PARTICIPANTS

We studied 1025 community-dwelling men median age 75.1 years at baseline with 8.6 years of follow-up.

MEASUREMENTS

Baseline and follow-up T, DHT and E2 were assayed using mass spectrometry. Physical performance was assessed at follow-up. Correlations and covariate-adjusted P-values were determined.

RESULTS

Longitudinal change in T was -2.0%/year, DHT -7.2%/year, LH +7.5%/year, SHBG +5.6%/year while E2 remained stable. Annualized increases in LH correlated with decreases in T and DHT (r = -.20, P < .0001 and r = -.12, P = .0035, respectively). Higher baseline T correlated with better physical performance at follow-up (eg, Step test r = .07, P = .03), as did higher baseline DHT (eg, time to sit-stand [TSS] r = -.07, P = .01). Larger annualized increases in LH predicted poorer physical performance at follow-up (eg, TSS r = .14, P = .001). Higher T at follow-up was associated with better physical performance (eg, TSS r = -.07, P = .04), as were higher DHT and lower LH. At baseline, 24 men (2.4%) had abnormally high LH (>16 IU/L); at follow-up, 175 (17.4%) had high LH of whom 70 had low T (<6.4 nmol/L).

CONCLUSIONS

Annualized increases in LH are associated with declines in T and DHT, and predict poorer subsequent physical performance in oldest old men. Men transitioning from 8th to 9th decades exhibit biochemical evidence of progressively impaired testicular endocrine function, warranting further evaluation.