A recent study of a male population explores the relationship between testosterone and erectile function. As suspected, higher levels of testosterone equals a better erection and improved sex drive. This study also helps to explain the different types of blood tests used to check testosterone, and why it is important for men and women to have more than just the total testosterone checked (also known as serum testosterone).

The study observed over 700 men from a specific population (population-based study) and established a correlation between a man’s testosterone level and his erectile function. The men in the study were followed for a period of 4 years and were selected to participate after receiving a comprehensive survey and baseline examination designed to narrow down the participants. Erectile function was determined by having each participant complete the widely used IIEF erectile function questionnaire in addition to blood testing. The men had to have been “in a stable sexual relationship for at least 6 months” at the time of the study. Their IIEF results helped to quantify their level of erectile dysfunction (ED) into three categories; none, mild, and moderate to severe (ED).

You can take the IIEF erectile function questionnaire used in this study by clicking the link below. What is your IIEF erectile function score? http://defymedical.com/services/sexual-health/326 Results will generate a score that can be used to recommend the next clinical step towards treatment.

The blood tests performed in the study include measurements of total testosterone, free testosterone, bio-available testosterone, and a protein called sex hormone binding globulin (SHBG). Many men (and women) along with their primary care doctors focus on just total testosterone, which measures the total sum of both bound and unbound testosterone. There is a difference between bound and unbound testosterone. Your body cannot use all of the testosterone measured in a total testosterone test. SHBG is a protein which can attach to testosterone very tightly which prevents testosterone from entering your cells. Any testosterone attached to SHBG would be considered bound, which the body cannot use. The level of SHBG was tested along with testosterone in this study. There are other proteins which can also bind to the testosterone molecule, such as albumin. Albumin does not bind as tightly as SHBG and therefore can quickly become unbound so that testosterone can be used by your cells. Free testosterone describes the testosterone which is not bound by any proteins and is available to be immediately used. Bio-available testosterone is a measurement of both free testosterone and also testosterone bound to albumin which, as mentioned, is easily separated so that the testosterone becomes available for use (free) when needed. Your body can use bio-available testosterone but it cannot use testosterone bound by SHBG.

This study explored the relationship between testosterone, our primary sex hormone, and erectile function. The conclusion showed a clear cause-effect relationship between the two. This is important to know since erectile dysfunction (ED) “is a worldwide disorder that affects millions of men” and has a negative influence on quality of life. If this relationship is not understood then ED treatments can fail for many men without understanding why. For example, PDE-5 inhibitors (Viagra, Cialis, Levitra) are commonly prescribed medications to treat ED. They work by inhibiting the enzyme (PDE-5) that prevents nitric oxide from relaxing the spongy erectile tissue in the penis (corpus cavernosum). Nitric oxide is released in the penis when a man is sexually aroused. Studies show that PDE-5 inhibitors like Viagra work more efficiently when there is a sufficient amount of testosterone present. These medications are more likely to fail if a man has low testosterone. Interestingly there is a positive relationship between testosterone and nitric oxide. Aging men who are experiencing ED should request to have a testosterone blood test to see if low testosterone, or more specifically low free-testosterone is the cause. The study came to the conclusion that “men with low free testosterone and high SHBG were at the highest risk of ED”. Remember, free testosterone is not bound by proteins and can be immediately used to support an erection and improve overall sexual performance.

This study emphasizes why it is important to always blood test both total and free testosterone. It can be additionally beneficial for some men experiencing poor erectile function to also blood test sex hormone binding globulin (SHBG), and Dihydrotestosterone (DHT)-an androgenic byproduct of testosterone. Androgens are shown to help maintain healthy erectile function in aging men (Testosterone is also an androgen). Testosterone in a younger man plays a role in the development of sex organs and male characteristics, such as the voice deepening and increase in body hair. After these tasks have been completed testosterone continues to play a role in the maintenance of erectile function and sex drive in aging men.

There can be many factors leading to erectile dysfunction but amongst all the causes it was common to find a deficiency or insufficiency of testosterone. It is important to first check testosterone levels when experiencing ED. Testosterone replacement therapy can be prescribed by a trained doctor to help restore low levels but first you must determine if your low testosterone may be caused by lifestyle habits, such as alcohol or drug use, or by disease. Restoring testosterone to a good level can help improve your erectile performance and libido.

To download the full study as a PDF for free please visit our clinical study library by clicking on the link below. The study is listed under the title “Sex Hormones Predict the Incidence of Erectile Dysfunction: From a Population-Based Prospective Cohort Study (FAMHES)”. You can also email [email protected] to request a PDF copy.

Clinical study library: http://defymedical.com/resources/clinical-studies/24-testosterone-replacement-therapy

Reference: Luo, Y., Zhang, H., Liao, M., Tang, Q., Huang, Y., Xie, J., Tang, Y., Tan, A., Gao, Y., Lu, Z., Yao, Z., Jiang, Y., Lin, X., Wu, C., Yang, X. and Mo, Z. (2015), Sex Hormones Predict the Incidence of Erectile Dysfunction: From a Population-Based Prospective Cohort Study (FAMHES). Journal of Sexual Medicine. doi: 10.1111/jsm.12854

Other references used:

The role of testosterone in erectile function and dysfunction. L. Gooren, MD, PhD, Available online 7 September 2006

Combining Testosterone and PDE5 Inhibitors in Erectile Dysfunction: Basic Rationale and Clinical Evidences. Emanuela A. Greco, Giovanni Spera, Antonio Aversa. Department of Medical Pathophysiology, University of Rome “La Sapienza”, 00161 Rome, Italy. Available online 13 July 2006

Published in Defy Medical Blog