The New Brain

How your brain—and our understanding of it—are constantly changing.

Low Testosterone: Where’s the Beef?

New studies question the belief that testosterone levels are related to sex.

We’ve all seen the commercials.  A smart-looking fifty-something couple gazes into each other’s eyes in wishful anticipation of romance, the guy’s randy desires undermined by some unspoken inadequacy reflected in a sympathetic but wistful expression on his lady’s face.  Then the answer in a pill or an underarm cream!  It’s a cure for a disorder you didn’t know you had--low T (testosterone).  But where’s the beef?  (If you don’t get the reference you are in the wrong demographic, but read on, the TV scenes may play out in your own future.)

            The lore of love potions permeates human history, but are past superstitious beliefs in witch’s brews being supplanted by modern respect for science and now being exploited by the pharmaceutical industry for greater profit?  It goes without saying that if a person has a diagnosed hormonal imbalance, drugs to correct the disorder are medical miracles, but what is the evidence to support the assertion that if you are not getting enough satisfaction in the bedroom, your problems will be solved by boosting levels of the “male” hormone in your otherwise healthy body; a body which has given you no other indication that your T level could have secretly sagged? 

Find a Therapist

Search for a mental health professional near you.

            Psychologist Sari van Anders, in the Neuroscience Program at the University of Michigan in Ann Arbor, conducted an interesting study on testosterone and sexual desire in healthy women and men, which is published in the journal Archives in Sexual Behavior.  The findings and a study by another group just published, challenge the assumption of any clear or simple link between testosterone and sexual desire in men or women. 

            It is easy to see why testosterone levels would be correlated with sexual desire.  The sharp rise in this hormone in the male body launches puberty and the onset of mature sexual behavior.  “It’s what puts hair on a man’s chest.  It is the force behind his sex drive,” you will read in men’s magazines and on-line.   But hold on, the arguments in these TV ads do not necessarily follow from the role that this hormone has in the biological process of maturation.  Moreover, levels of testosterone decline naturally with age, presumably for good reason. 

            It is important to get the scientific facts right when it comes to futzing with the body’s hormones.  Eye of newt and whatever else goes into love potions may be useless but harmless.  That’s not necessarily so when forcing powerful sex hormones into the body.  There are many health risks of elevating testosterone in a man’s body, including raising the red blood cell count to dangerous levels, enlarging breasts (an ironic outcome), emotional and behavioral changes, and accelerating the growth of prostate and other cancers that increase in middle and old age. 

            Much of the research on T and sexual behavior is performed on animals, but we cannot simply translate studies of sexual behavior in lab rats to sexual behavior in humans.  In laboratory animals mating behavior is more directly regulated by sex hormones, but in people sexual desire is a far more complex issue, which involves social factors, psychological dynamics, stress, and alternative behaviors for sexual release that complicate the situation.  Even in animal studies an association between T and sexual behavior is complex and modified by social context.  For example, drugs blocking the effect of T in some animal studies can decrease sexual interest, but social pressure moderates the link. 

            In human studies, a simple link between T and sexual desire is not as simple as the TV ads would have you believe.  In women, hormonal contraceptives that decrease T do not necessarily decrease sexual desire.  In healthy men, T blockers have mixed effects in studies of sexual behavior. In studies supplementing T the results are also mixed, in part because artificial administration of T does not have the same physiological effect on the body as natural fluctuations in the hormone.  The results of a new clinical trial just published on-line in advance of print in the journal Andrology found that even in men who have low levels of T in their blood and suffer erectile dysfunction (ED), T supplements had no effect in improving mood or well-being.  The study by Spitzer and colleagues at Boston University School of Medicine involved 140 men between the ages of 40 and 70 in a placebo controlled randomized trial in which the men applied a gel that did or did not contain any T.  Whether the gel did or did not contain T was unknown to both themselves and their physicians.    This study showed that even in men with diagnostically confirmed low levels of T in their blood stream, testosterone gel “was not associated with improvements in sense of well-being or mood.” 

            Another complication is that T is hardly the only hormone involved in sexual arousal and behavior, and complex interactions are expected among various hormones.  The stress hormone cortisol, for example, which is secreted by the adrenal glands, will affect sexual desire in complex ways.  Although this and other hormones are less well studied, some studies associate cortisol with increased sexual arousal, but they show that cortisol can interact with T to modify the effects of the sex hormone.  In van Anders’ study, 196 healthy men and women were studied, and the amount of cortisol and testosterone in their saliva was measured to seek a correlation between sexual desire and levels of these hormones.  What van Anders’ study found was that there was no significant correlation between T and sexual desire in men, even when other psychological variables affecting sexual desire were controlled.  Men did have a higher sexual desire in general compared with women, but masturbation frequency, rather than the concentration of T in their saliva, turned out to be the overriding factor on the intensity of their sexual urges.  Masturbation is linked to T levels in a number of studies, but this does not translate into increased sexual desire or sexual activity with a partner, because sexual intimacy with another person is influenced by stress, social situation, mood, self-esteem, loneliness, and general well-being. 

            Things with women are somewhat more complicated.  Sexual desire in women was negatively associated with T in this study; that is, high T levels translated into less desire.  However, this paradoxical association only appeared to be the case if stress and cortisol levels were not considered.  Why?  Much of the T in a women’s body is released from her adrenal glands along with the stress hormone cortisol.  Men, who have higher T to begin with, release it into their blood stream from their testicles.   Therefore, men would be less influenced by the relatively small amount or T secreted from their adrenal glands, but for women, this would be a significant source of the hormone released during stress.  As stress and cortisol rise, sexual desire decreases despite the uptick in her T levels.  Women with low T in this study did have a lower frequency of masturbation, but sexual behavior with a partner could not be linked directly to their levels of testosterone, because as said, that is a much more complex issue.   Consider also those other “female” hormones, such as estradiol, were not measured and these would be expected to have effects on sexual desire and activity. 

            “These results challenge ongoing assumptions of the importance of T in the basic biology of healthy men…” writes van Anders.  As they say in the fine print, ask your doctor.  Be careful to listen to what he or she says and resist the advertising pressure to grasp a pharmacological treatment for a complex social/psychological/sexual behavior before establishing through rigorous laboratory analysis that there is indeed a deficiency in your body’s chemistry.

            There are some other provocative issues raised by this research.  If these studies are correct, how is it possible that a drug treatment would be implemented and mass marketed on TV without solid scientific evidence to support it?  Secondly, do what doctors consider “normal” concentrations of natural compounds in the body change as drugs become available (such as cholesterol-lowering medications) that make it possible to artificially change their levels in the body?  You have to wonder why that might happen as you watch medications being hawked to the masses on TV as if they were chia pets.

 

References

 Spitzer, M., et al., (2013)  The effect of testosterone on mood and well-being in men with erectile dysfunction in a randomized, placebo-controlled trial.  Andrology doi: 10.1111/j.2047-2927.2013.00075.x

 

van Anders, S.M. (2012)  Testosterone and sexual desire in healthy women and men.  Arch. Sex. Behav. 41: 1471-`484.

R. Douglas Fields, Ph.D., is the Chief of the Nervous System Development and Plasticity Section at the National Institute of Child Health and Human Development and the author of The Other Brain. more...

Subscribe to The New Brain

Current Issue

Love & Lust

Who says marriage is where desire goes to die?