We expect testosterone levels to decrease as we age.

But did you know that testosterone levels in *age-matched* populations of American men have trended lower over the past generation?

Two landmark studies, one in older men and one in younger men, show that testosterone levels in American men have declined sharply over the past 30 years.

The first study was published in the Journal of Clinical Endocrinology and Metabolism in 2007 (Travison et al). They measured average total testosterone levels of different groups of men, aged 45-80, across three time periods:

1987-1989: 501 ng/dl

1995-1997: 435 ng/dl

2002-2004: 392 ng/dl

→ 22% drop in less than 20 years.

This change was highly statistically significant, even after controlling for age, BMI, and other potential confounding factors.

The second study, published in the European Association of Urology in 2020 (Lokeshar et al), showed a significant decrease in testosterone among American men with an average age of 26 from 1999-2016.

1999: 605 ng/dl

2016: 451 ng/dl

→ 25% decline in under 20 years.

The percentage of young men who had testosterone deficiency (defined as a level < 300 ng/dL) increased from 9% in 1999 to 20% in 2016.

These studies received some attention in the lay media, but many of the so-called experts that were interviewed dismissed the results, attributing the drop in testosterone to a rise in obesity.

Clearly these experts did not read the studies. Because while it is true that obesity is associated with low testosterone levels, in these studies the authors specifically point out that the results remain significant even after controlling for obesity.

It’s unclear why testosterone levels have fallen so dramatically over the last generation, but there are many suspected culprits.

Endocrine disrupting chemicals (EDCs), including those found in ever-present plastics, exposure to blue light, exposure to cell phones and wi-fi, chronic stress, poor sleep, obesity, and other unknown factors all may be playing a role.

Getting your testosterone levels checked is essential to your health.

Some people may feel hormone replacement therapy is “unnatural”.

If that’s you…stop scrolling for a moment, set your phone down, and take a look at your surroundings.

Are you living in a “natural” world?