The key wording in the title and throughout the article is "day to day" testosterone associations. If you understand what they are implying and not implying by

The key wording in the title and throughout the article is "day to day" testosterone associations. If you understand what they are implying and not implying by that, the paper makes sense, but it is very poorly written in its omission of discussion of something it mentions only once in passing, the male circadian testosterone cycle (which it does describe how it tries to control for, but if you read this paper without understanding that, you won't really understand its findings.) Women's hormones are well-understood to cycle monthly and it affects a variety of things including desire. What nobody ever told me growing up and the culture still doesn't talk about is that men, rather than having a monthly cycle have a daily cycle with huge testosterone swings that get lower in the afternoon and start rising dramatically in the early morning hours.[1] This is something that correlates greatly with the "morning erection" and sexual urges (including porn) in the morning hours that many men experience. (And which at least some advertisers clearly understand, judging based on the ads shown to me at different times of day.) As they themselves mention, "Our measures of sexual desire did not differentiate between dyadic and solitary desire", nor did they control for "solitary desire" activity and its impact on testosterone levels. It is useful to have a study that looks at day-to-day testosterone as opposed to weekly/monthly/hourly, but I also found it frustrating there was no graph that showed based on their data how much testosterone fluctuated during the 31 days of month for their subjects (with some standard deviation bars or something). I know that wasn't what they were studying but I found it a bit hard to understand their findings without that. [1] https://www.researchgate.net/figure/Serum-testosterone-concentrations-during-a-24-h-period-demonstrating-that-young-men_fig2_359144415 https://www.researchgate.net/figure/Serum-testosterone-conce...