Not quite. According to https://www.usatoday.com/story/news/factcheck/2022/05/09/fact-check-testosterone-levels-lower-25-1999-2016/7381735001/
The article refers to data from studies in 2007 and 2021, both of which looked at the testosterone levels of men in the United States.
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Both studies observed significant reductions in testosterone levels over time. In the 2007 study, testosterone decreased by about 22% when comparing 1985-1987 levels to those from 2002-2004. In the 2021 study, researchers found a roughly 25% decrease between 1999 and 2016.
These numbers mean that the claim in the Twitter post isn’t true, according to Dr. Ranjith Ramasamy, a urologist at the Miami University Miller School of Medicine and author of the 2021 study.
“Neither of these studies assessed men over the last two decades, and the percent change was not close to 50%, so it is inaccurate to say that average testosterone has fallen almost 50% over the last 2 decades,” Ramasamy wrote in an email.