Men feel less pain than women. That’s not a judgment call—tests have proven it. For instance, among patients who have chronic pain conditions (such as arthritis or nerve damage) or who undergo identical surgical procedures (such as a knee replacement), women tend to experience more pain than men.

It’s not just that men generally are raised to be more stoic or that women are raised to be more sensitive. Rather, a key element in this discrepancy seems to be the hormone testosterone. Though women do produce some testosterone, men naturally produce much more of it. Animal studies support this idea that testosterone protects against the perception of pain. Male mice whose production of testosterone is blocked demonstrate increased sensitivity to pain…and when the animals’ testosterone levels are returned to normal, their response to painful stimuli is reduced.

What does this mean for people whose testosterone levels are abnormally low? They may have increased pain perception. And ironically, opioids—the very drugs that are often used to relieve pain—can significantly reduce testosterone levels, creating a vicious cycle in which patients may require more and more medication to deal with their pain. Now a fascinating new study suggests a possible way to break this cycle…

TESTING TESTOSTERONE

Men produce testosterone in their testicles, and their normal range of serum testosterone (the total amount in the blood) is between 300 nanograms per deciliter (ng/dL) and 1,000 ng/dL. In women, testosterone is produced in the ovaries, and their normal serum testosterone range is 15 ng/dL to 75 ng/dL. Opioid pain-relieving medications such as morphine, codeine, fentanyl and oxycodone (Oxycontin) are known to reduce testosterone production, sometimes decreasing it to undetectable levels in the blood.

For the new study, researchers enrolled men who were taking opioid medication for chronic pain and whose average testosterone level was 228 ng/dL. Before treatment, all the men underwent various tests to measure their perception of and tolerance for pain. Then they were randomly assigned to one of two groups. In one group, each man used a transdermal (applied to the skin) testosterone gel daily to bring his testosterone level up in the desired range of 500 ng/dL to 1,000 ng/dL. The other group of men used a placebo gel.

After 14 weeks, the tests were repeated to gauge any changes in the men’s reactions to…

  • Mechanical pain. For this test, blunt-edge pins were applied to the forearm. Compared with their scores at the start of the study, the placebo users reported an average increase in perceived pain of eight points on a 100-point scale, while the testosterone users reported a decrease in pain of five points, on average.
  • Pressure pain. A device called an algometer was placed on the thumb or on the upper back. The algometer exerted increasing amounts of pressure, measured in watts, until a participant said that he could not tolerate the discomfort any longer. In the placebo group, the men’s ability to withstand the pain decreased by an average of 70 watts from the start to the end of the study…but among the testosterone users, tolerance increased by 25 watts.
  • Cold tolerance. Here the challenge for each man was to keep his hand immersed in ice-cold water for as long as possible. At the end of the study, the men who had received testosterone were able keep their hands in the water an average of 10 seconds longer than men who had received the placebo.

IF YOU ARE IN PAIN…

This study could hold a clue as to why people often become dependent on opioid medication. A cycle is created in which the drug reduces testosterone levels, thereby increasing pain…which in turn leads to a need for even more medication and increases the risk for addiction. It’s possible that testosterone replacement therapy could help break this cycle by reducing pain perception and increasing pain tolerance. Additional studies are needed to confirm that theory.

Not all cases of low testosterone are due to opioid use. Other possible causes include obesity, various endocrine disorders, certain inflammatory diseases, excess iron in the blood, and chemotherapy or radiation for cancer treatment. Whether testosterone replacement also might help alleviate pain in these conditions remains to be seen.

Important: The findings from this study do not suggest that patients with normal hormone levels should be given extra testosterone to treat their pain. Excess testosterone can increase the risk for sleep apnea and heart disease and may lead to elevated red blood cell counts.

However, if you have a chronic painful condition or if you experience pain that seems out of proportion to an injury or illness, it is worthwhile to talk with your doctor about having your testosterone level checked and treated if it turns out to be too low.