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.

Reproductive hormone levels, androgen receptor CAG repeat length and their longitudinal relationships with decline in cognitive subdomains in men: The European Male Ageing Study.

OBJECTIVE: It has been proposed that endogenous sex hormone levels may present a modifiable risk factor for cognitive decline. However, the evidence for effects of sex steroids on cognitive ageing is conflicting. We therefore investigated associations between endogenous hormone levels, androgen receptor CAG repeat length, and cognitive domains including visuoconstructional abilities, visual memory, and processing speed in a large-scale longitudinal study of middle-aged and older men. METHODS: Men aged 40-79 years from the European Male Ageing Study (EMAS) underwent cognitive assessments and measurements of hormone levels at baseline and follow-up (mean = 4.4 years, SD ± 0.3 years). Hormone levels measured included total and calculated free testosterone and estradiol, dihydrotestosterone, luteinizing hormone, follicle-stimulating hormone, dehydroepiandrosterone sulphate and sex hormone-binding globulin. Cognitive function was assessed using the Rey-Osterrieth Complex Figure Copy and Recall, the Camden Topographical Recognition Memory and the Digit Symbol Substitution Test. Multivariate linear regressions were used to examine associations between baseline and change hormone levels, androgen receptor CAG repeat length, and cognitive decline. RESULTS: Statistical analyses included 1,827 and 1,423 participants for models investigating relationships of cognition with hormone levels and CAG repeat length, respectively. In age-adjusted models, we found a significant association of higher baseline free testosterone (ß=-0.001, p=0.005) and dihydrotestosterone levels (ß=-0.065, p=0.003) with greater decline on Rey-Osterrieth Complex Figure Recall over time. However, these effects were no longer significant following adjustment for centre, health, and lifestyle factors. No relationships were observed between any other baseline hormone levels, change in hormone levels, or androgen receptor CAG repeat length with cognitive decline in the measured domains. CONCLUSIONS: In this large-scale prospective study there was no evidence for an association between endogenous sex hormone levels or CAG repeat length and cognitive ageing in men. These data suggest that sex steroid levels do not affect visuospatial function, visual memory, or processing speed in middle-aged and older men.

Lower vitamin D levels are associated with depression among community-dwelling European men.

Low serum 25-hydroxyvitamin D (25(OH)D) and elevated parathyroid hormone (PTH) levels have been linked with depressive symptoms among adults in various clinical settings. Data in generally healthy, community-dwelling individuals remain inconclusive. We investigated whether depression was associated with 25(OH)D and/or PTH in a sample of middle-aged and older men (n = 3369; mean age 60 ± 11) participating in the European Male Ageing Study, and whether any associations were explained by lifestyle and health factors. The Beck Depression Inventory-II (BDI-II) was used to screen for depression, and serum 25(OH)D and PTH levels measured by radioimmunoassay. Univariate analysis revealed that 25(OH)D levels were lower (p < 0.001) and PTH higher (p = 0.004) in people with depression. In age- and centre-adjusted linear regressions a higher BDI-II score was significantly associated with lower levels of 25(OH)D (p = 0.004). After adjustment for lifestyle and health factors this relationship was attenuated but remained significant (p = 0.01). Using multivariable logistic regression the odds for depression increased approximately 70% across decreasing 25(OH)D quartiles (p (trend) = 0.04). There was no independent association between PTH and depression in any of the multivariable regressions. Our results reveal an inverse association between 25(OH)D levels and depression, largely independent of several lifestyle and health factors. Further studies are required to determine whether higher levels of vitamin D have an antidepressant effect in older adults.