Testosterone replacement therapy (TRT) and libido are often discussed together as both are closely related. There is a correlation between low testosterone and lowered desire for sexual thoughts/fantasies and sex acts including sexual intercourse.
It is well established from clinical experience and studies/literature that libido tends to decrease with age in both men and women. The peaks for sexual desire in all males are often during puberty. When males attain puberty there is a sudden and massive surge of testosterone/DHT and oestradiol. All these hormones aid in stimulating physical growth and primary and secondary sexual characteristics development, such as testicular descent, penile growth, and vocal changes as well as secondary hair growth, increased musculature growth also increased libido.
This large surge or increased fluctuation of these hormones causes these amplified outcomes. This indicates certainly a relationship between testosterone and sexual desire. The inverse outcome is seen in aging men, where a reduction in libido alongside low testosterone is noted as we get older. Libido is a complex multi-factorial process. Low libido is not entirely due to low testosterone, but it often manifests together. In men, having an optimal amount of free testosterone for their age will allow for a complex mechanism, of action to occur to cause an erection. The mechanism of action incorporates hormonal pathways, both the sympathetic and parasympathetic nervous systems as well as somatosensory, supraspinal and central neural pathways. This indicates the correlation of hormonal levels with physical arousal as well as sexual desire. Optimal hormonal circumstances will affect your physical, and sexual manifestations and your sexual desire/thoughts.

Does TRT improve libido?
It will certainly help improve a low libido for a man with low testosterone levels. Be informed that TRT will have the same effect on libido, as it does on all other aspects of our lives, it won’t cure or fix everything. TRT will normalize your male androgen profile and restore the balance of your overall steroid hormone profile to allow you to do the things necessary to restore order in other areas of your life which will affect libido such as sleep, stress, anxiety etc.

Take Home Message
TRT can help a decreasing libido as it will raise both your total and free testosterone levels whilst ensuring an appropriate balance of your oestradiol levels. This would provide a conducive hormonal profile to normalize/ improve low libido. What it will not do is make you constantly think about, be ready for or want to engage in sex acts/thoughts or fantasies, which is completely normal for healthy males with optimal testosterone levels. Libido is rhythmical, it is normal for it to wax/wane relative to multiple extraneous variables secondary to our male androgen profiles. Consulting your healthcare practitioner to further understand this issue and investigate hormonal levels is highly recommended. Your doctor would be able to check your hormonal levels by doing a simple blood test. An optimal and balanced hormonal profile would improve and reduce the deterioration of low libido.