Throughout the world, testosterone levels are decreasing, and most people don’t know this or understand the significance of this trend. It’s problematic on multiple levels — for reproduction, health and longevity, libido, and proper fetal development during pregnancy. While researching and writing our new book Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race, we discovered research showing not only that sperm counts and testosterone levels are declining, but they’re doing so in tandem and at an alarming rate of 1 percent per year in Western countries.
At first blush, this may not sound like a big deal, but it is. It adds up to more than a 10 percent decline per decade and more than a 50 percent drop over 50 years. Meanwhile, rates of testicular cancer and the prevalence of erectile dysfunction have been increasing at a similar rate, and so have miscarriage rates in the United States. It’s not a pretty picture.
Its Not Just About Sperm Counts; Reproductive Health Is Also at Stake
It’s noteworthy that the use of testosterone replacement therapy has increased dramatically among younger men, many of whom are taking it to boost their energy and muscle mass. In fact, a study in the April 2017 issue of the Journal of Urology found that the use of testosterone replacement therapy had increased fourfold among men between the ages of 18 and 45 and threefold among older men from 2003 to 2013. What men don’t realize is that with testosterone replacement, a decline in sperm production occurs, so they’re working at cross-purposes with their best interests if they want to have children.
The Hormone Testosterone Plays a Role in Women’s Health as Well as Men’s Health
People often think of testosterone as a “male” hormone, but girls and women also produce testosterone in their ovaries (in guys it’s made by the testes); however, women produce it in much smaller amounts than men do. In both sexes, the hormone affects energy levels, cognitive function, libido, and sexual function. When women’s lack of sexual desire is persistent and distressing, it’s called hypoactive sexual desire disorder, and according to a consensus statement in a 2019 issue of the NEJM Journal Watch Women’s Health, “Testosterone therapy is indicated only for postmenopausal women with hypoactive sexual desire disorder (HSDD), with evidence suggesting moderate therapeutic effects.” So clearly testosterone plays a crucial role in women’s sexual function, just as it does for men.
For women, there’s a sweet spot for testosterone levels at various stages of life. Too much or too little can send reproductive health and development in the wrong direction. For example, when a woman is pregnant, in order for her baby to develop properly, it needs to be exposed to the right amount of testosterone in the womb at the right time — it’s the Goldilocks conundrum in play.
Here’s where things get tricky: Research has found that if a male fetus gets too little testosterone while in the womb, his genitals and his brain are likely to become less male-typical. By contrast, if a female fetus is exposed to too much testosterone in utero — perhaps because she has congenital adrenal hyperplasia, a genetic condition — her brain and genitals will be less female-typical after she’s born. In other words, exposure to testosterone has the ability to push a developing fetus along the continuum between male and female. Once they’re born and start to grow up, these hormonal effects can influence the way children perceive themselves in terms of gender; what’s more, they can affect the kids’ activity preferences (playing with cars and trucks vs. dolls, for instance) and their style of play (rough-and-tumble vs. gentle, for example).
In addition, when girls and women have elevated levels of testosterone — as they do with polycystic ovary syndrome (PCOS), which research suggests is increasing in incidence — they often have irregular periods, fertility challenges (including a higher rate of miscarriages), hair in unwanted places, acne, and excessive weight gain. And if they do have babies, these women’s baby girls are likely to have a higher body mass index (BMI), according to research published in April 2016 in?Reproductive System & Sexual Disorders: Current Research.
Why Testosterone Levels Are Out of Whack
Now that you know how testosterone levels affect women’s and men’s reproductive health, here’s the shocker: All the reproductive changes that have been occurring in recent years are too synchronous to be a coincidence. These changes are partly driven by poor lifestyle choices (such as smoking, binge drinking, and the like) but more so by the hundreds of chemicals that people are exposed to on a daily basis throughout the world, as we illustrate in our book.
Will Unregulated Chemicals Continue to Compromise Fertility?
Not only are these reproductive health changes interconnected, but they are largely driven by a common cause: the presence of endocrine disrupting chemicals (EDCs) in our world. These hormone-hijacking chemicals — which include phthalates, bisphenol A, perfluoroalkyl and polyfluoroalkyl substances (PFAS), and flame retardants, among others — have become ubiquitous in our modern world. We ingest them in the air we breathe, our food and water, and the products we slather on our skin. That’s because they’re present in plastic water bottles and food packaging, nonstick cookware, electronic devices, cosmetic and personal-care products, cleaning supplies, and many other items that we use regularly.
Inside the human body they are playing havoc with the building blocks of sexual and reproductive development and reproductive health. These chemicals began being produced in increasing numbers after 1950, which is when sperm counts, testosterone levels, and fertility began to decline. Unbeknownst to many people, these chemicals are altering our testosterone levels, along with estrogen levels, and having detrimental effects on human reproductive health and development.
Most people also don’t realize that these chemicals are largely unregulated: Unlike drugs, which must have a proven record of safety and effectiveness before they’re allowed onto the market, in the United States chemicals are presumed to be safe until they’re proven otherwise. This means that myriad chemicals that are used to manufacture an incredible array of consumer products are largely unregulated. In other words, we’ve been using each other and our unborn children as unwitting guinea pigs for EDC exposures — and this experiment is taking a toll on our reproductive health and potentially the future of the human race.Shanna Swan, PhD, is one of the world’s leading environmental and reproductive?epidemiologists and a professor of environmental medicine and public health at the Icahn School of Medicine at Mount Sinai in New York City. She and Stacey Colino, a frequent contributor to Everyday Health, are coauthors of Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race, published in February 2021.
Important: The views and opinions expressed in this article are those of the author and not Everyday Health.