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Open access

Morten Ruge, Tea Skaaby, Anna-Maria Andersson, and Allan Linneberg


Reduced total hours of sleep and low quality of sleep have been suggested to be associated with low levels of male hormones. Few studies have examined the association between excessive sleep and male reproductive hormones.


To investigate the association of total hours of sleep and quality of sleep with serum levels of total, bioavailable and free testosterone (tT, bT and fT), sex hormone-binding globulin (SHBG) and dehydroepiandrosteron-sulfate (DHEAS).


Serum levels of tT, SHBG and DHEAS were measured with immunoassays in a cross-sectional population-based study of 2095 males. bT and fT were calculated in accordance with Vermeulens method. Information on total hours of sleep and sleep quality was obtained by questionnaire. Linear regression was used to calculate hormones according to total hours of sleep and the results were expressed as β-estimates and 95% confidence intervals (CI). The adjustment in the multivariable models was constructed taking age, BMI, smoking, alcohol intake and physical activity into account.


Excessive sleep (>9 h) compared to 7–9 h of sleep was significantly associated with lower tT, bT and fT, but not with SHBG or DHEAS, after multivariable adjustment. These significant associations were also found in our analyses with hormones as continuous variables but no associations were found in our general additive model analyses.


In this cross-sectional study in men, excessive sleep associated with lower levels of male reproductive hormones. Longitudinal studies are needed to determine the causal direction of the observed association between excessive sleep and lower male reproductive hormones levels.

Open access

Stine A. Holmboe, Ravi Jasuja, Brian Lawney, Lærke Priskorn, Niels Joergensen, Allan Linneberg, Tina Kold Jensen, Niels Erik Skakkebæk, Anders Juul, and Anna-Maria Andersson


Calculating the free testosterone level has gained increasing interest and different indirect algorithms have been suggested. The objective was to compare free androgen index (FAI), free testosterone estimated using the linear binding model (Vermeulen: cFTV) and the binding framework accounting for allosterically coupled SHBG monomers (Zakharov: cFTZ) in relation to cardiometabolic conditions.


A prospective cohort study including 5,350 men, aged 30-70 years, participating in population-based surveys (MONICA I–III and Inter99) from 1982-2001 and followed until December 2012 with baseline and follow-up information on cardiometabolic parameters and vital status.


Using age-standardized hormone levels, FAI was higher among men with baseline cardiometabolic conditions, whereas cFTV and cFTZ levels were lower compared to men without these conditions as also seen for total testosterone. Men in highest quartiles of cFTV or cFTZ had lower risk of developing type 2 diabetes (cFTV: HR=0.74 (0.49-1.10), cFTZ: HR=0.59 (0.39-0.91)) than men in lowest quartile. In contrast, men with highest levels of FAI had a 74% (1.17-2.59) increased risk of developing type 2 diabetes compared to men in lowest quartile.


The association of estimated free testosterone and the studied outcomes differ depending on algorithm used. cFTV and cFTZ showed similar associations to baseline and long-term cardiometabolic parameters. In contrast, an empiric ratio, FAI, showed opposite associations to several of the examined parameters and may reflect limited clinical utility.