This post is prompted by a new American Urological Association paper below [1].
"TRENDS IN SERUM TESTOSTERONE LEVELS AMONG ADOLESCENT AND YOUNG ADULT MEN IN THE UNITED STATES"
My generation of males had no fertility problems as I recall. Quite the reverse, in fact. A generation later & one hears "they are trying for a baby." I became interested in this when my son was 'trying'. Many, many papers out there on declining male fertility, & there seems to be no end to the decline.
Oddly, I don't recall anything on a parallel decline in testosterone [T].
The T value that seems to be used for hypogonadism these days is 350 ng/dL. Perhaps that 350 ng/dL limit is akin to the vitamin levels needed to prevent scurvy, rickets & beriberi - one would want to be a bit higher in the observed range.
With that 350 in mind, look at the graph in the link. The average T level in young men in 1999-2000 was close to 600 ng/dL. The decline seems to have already linear at this point. By 2015-16 it had fallen ~200 points. It may be alreay at the 350 mark.
Although increasing BMI explains much of that: "Even in men with normal BMI (18.5-24.9), TT levels have declined from 664.79 ng/dL to 529.24 ng/dL between 1999-2000 and 2015-2016"
My concern is not for the future of the human race, but for the effect on future PCa rates. Low T has been found to be a PCa risk factor.
-Patrick
[1] auajournals.org/doi/10.1097...
MP78-01 TRENDS IN SERUM TESTOSTERONE LEVELS AMONG ADOLESCENT AND YOUNG ADULT MEN IN THE UNITED STATES
Premal Patel , Richard Fantus , Soum Lokeshwar* , Joshua Halpern , Cecilia Chang , Atil Kargi , and Ranjith Ramasamy
View All Author Information
doi.org/10.1097/JU.00000000...
Tools
Share
Abstract
INTRODUCTION AND OBJECTIVE:
Testosterone deficiency has a prevalence of 10-40% among adult males and 20% among adolescent and young adult (AYA) men (males 15-39 as per the National Cancer Institute). With increasing prevalence of low testosterone in general population, we hypothesized that serum total testosterone (TT) levels will decline in AYA men. The objective of this study was to analyze serum TT levels in AYA males using data from the National Health and Nutrition Examination Surveys (NHANES) 1999-2016. We hypothesized that serum TT levels in AYA men have decreased over time.
METHODS:
NHANES is a nationally representative cross-sectional survey that examines the US population and over samples targeted populations, to obtain adequate samples for subgroup analysis and more reliable variable estimates. We found data cycles which had values for serum TT and analyzed changes in serum TT over time controlling for year of study, age, race, body mass index (BMI), comorbidity status, alcohol and smoking use, and level of physical activity. During the study periods, three different assays (Biotin-Streptavidin from 1999-2004, IS-Liquid Chromatography from 2011-2012 and High-Performance-Liquid-Chromatography Tandem Mass Spectrometry from 2013 onwards) were used; they have shown comparable testosterone values with only some additional accuracy in the latest modality.
RESULTS:
A total of 4,045 men had TT measured from 1999-2016. After controlling for confounders, TT was lower among men in the later (2011-2016) versus earlier (1999-2000) cycles (all p < 0.001). Mean TT decreased over time: 605.39 ng/dL, 567.44, 424.96, 431.76 and 451.22 for 1999-2000, 2003-2004, 2011-2012, 2013-2014 and 2015-2016, respectively (p < 0.0001). Elevated BMI was associated with reduced TT levels (p < 0.0001) with mean BMI increasing from 25.83, 27.21, 27.12, 27.81, 27.96 for 1999-2000, 2003-2004, 2011-2012, 2013-2014 and 2015-2016, respectively, p = 0.0006. Even in men with normal BMI (18.5-24.9), TT levels have declined from 664.79 ng/dL to 529.24 ng/dL between 1999-2000 and 2015-2016 (p < 0.05).
CONCLUSIONS:
This is the first study to report declining testosterone levels in adolescent and young adult men. Further studies are required to understand the etiology of low testosterone in AYA men.