Higher testosterone levels are more to do with mating competition than sexual desire
Upending long-held beliefs that testosterone levels regulate sexual desire, a new study has found that while the hormone plays a key role in reproductive success, elevated concentrations appear more intrinsically tied to 'courtship' - particularly in single men.
An international team of researchers led by the University of California, Santa Barbara has found that fluctuations in testosterone levels did not increase or decrease male sex drive, instead finding more nuanced ways in which it primes a male in their search for a mate and then, once partnered up, it has less of an impact.
In the study, 41 men aged 18 to 26 of varying relationship statuses - 27 single, 14 committed to a partner - were recruited for a 31-day trial that involved daily saliva analysis and self-reported responses to questions regarding sexual thoughts and desires, as well as the effort they put into dating or 'courtship.' The researchers used continuous time (CT) modeling in analyzing the saliva samples, due to the nature of how hormones are produced, in order to better chart shifts in sex drive and testosterone levels.
"In addition to testing same-day associations between testosterone and desire, our density of data collection allowed tests of time-lagged associations between the two variables," the team wrote. "Steroid hormones act in part via effects on gene transcription that can produce delayed effects; conversely, hormone production might be affected by events or behaviors that occurred several days earlier."
When they isolated the data of single men versus those with partners, some interesting nuances emerged. On days where the single men interacted with prospective partners, testosterone concentrations were higher, suggesting more effort was made to seek out a mate. Extensive studies on birds have found that during mating season, testosterone levels may be elevated in part due to competition between males, requiring more effort to successfully partner up. In primates, a similar pattern has been observed, with competition linked to a spike in testosterone in males under threat of losing a mate.
"Testosterone and cortisol concentrations were significantly higher in single versus partnered men," the researchers noted. "Exploratory analyses produced evidence that testosterone fluctuations in the normal range may positively predict day-to-day changes in men's mate attraction efforts among single men, especially given social interactions with potential mates.
"Future research could test replication of that pattern and seek to disentangle the possible causal pathways through which associations between testosterone and courtship effort may arise," the team added.
While the study certainly has its limitations - single men are more likely to interact with potential future mates than those with partners, generally, and saliva testing has many variables - it does counter the widespread perception of testosterone levels having a direct impact on sex drive. In the study, all participants had hormone concentrations in the normal range, which is in line with earlier research that showed only very low testosterone appeared to impact desire.
"These findings corroborate prior research in suggesting that men's sexual desire requires only a threshold amount of baseline testosterone above which testosterone changes do not reliably affect desire," the researchers noted. "Surprisingly few prior studies have provided data on within-subject relationships between men's natural testosterone production and their sexual desire.
So what does this mean? Well, mainly that we need more research. Despite men historically being overrepresented in scientific studies, hormone fluctuations and sex drive has been more comprehensively studied and in turn understood in the opposite sex. Much of the prior data attempting to link testosterone concentrations to sexual desire has been inconclusive - however, the widespread belief that there's a causal relationship prevails.
"This study provides direct, naturalistic evidence that day-to-day fluctuations in men's sexual desire are not significantly associated with daily fluctuations in their testosterone concentrations," the researchers wrote. "In other words, a man experiencing higher-than-usual testosterone concentrations on a given day does not typically exhibit higher-than-usual sexual desire on that same day."
The study warrants more research into the efficacy of testosterone-targeted supplements and other treatments for low sex drive.