Fibromyalgia and Male Physiology: Why It's Different

Hormones, Brain Chemistry, Sleep

A man holds his forehead and looks pained.
Men's physiology may make the experience of fibromyalgia different. Caiaimage/Chris Ryan/Getty Images

Men makeup only about 10 percent of those diagnosed with fibromyalgia, and research suggests that they have different symptoms than women. But why?

The answer to that could lie in men's physiology. Male hormones play a surprisingly big role in the experience of pain, and differences in brain chemistry and sleep may play into it, too.

Hormonal Differences

The most obvious difference between fibromyalgia in men versus women is hormonal.

In women, flares are often tied to the menstrual cycle, and hormonal events such as menopause or hysterectomy may trigger symptoms.

Certainly, men don't have such obvious hormonal events. So far, studies examining male hormonal fluctuations or abnormalities in fibromyalgia simply haven't been done, so we don't know what role, if any, these hormones play. Generally speaking, though, we do have evidence that male hormones impact pain in certain ways.

Testosterone, the primary male hormone, is thought to play a beneficial role when it comes to pain in general. Research suggests that it may help prevent muscle fatigue and, in combination with a certain protein, may help repair muscles after exercise. Male hormones may also affect other biological processes related to fatigue and pain.

We also know of gender-based differences in the stress hormone cortisol, which research suggests is low in fibromyalgia.

One study published in Health Psychology in 2008 showed that cortisol levels were different in happily married women than in their unhappily married counterparts while men didn't exhibit any differences based on marital happiness. Researchers speculated that this could explain why conditions involving low cortisol are more likely in women.

Brain Chemistry

The brains of men and women are not identical. One difference that may influence what fibromyalgia is like for each gender is the neurotransmitter (chemical messenger) serotonin.

Serotonin is believed to play a key role in fibromyalgia. Its areas of influence include pain, sleep, anxiety, and depression. Some research suggests that the serotonin system works differently in men than in women.

A 2008 study published in Neuroimage showed that men have fewer serotonin receptors (brain cells that respond to it) than women. However, the process of reuptake—which is essentially "recycling" so the neurotransmitter can be used again—may be more efficient in men.

Drugs that slow reuptake are commonly prescribed for fibromyalgia. They're called SSRIs (selective serotonin reuptake inhibitors) or SNRIs (serotonin-norepinephrine reuptake inhibitors. Two of the three drugs approved for this condition are SNRIs: Cymbalta (duloxetine) and Savella (milnacipran).

Because of the gender differences in the serotonin system, some doctors have suggested that these drugs be tested on men and women separately. This hasn't happened yet, but we do have anecdotal evidence that men and women respond differently to this class of medication.

A separate study published in Biological Psychiatry in 2007 showed that lowering the body's serotonin levels doesn't affect men and women in the same way. In women, it caused worsening mood and increased cautious behavior. Men didn't have mood changes at all but became more impulsive, the researchers say.

These kinds of differences, which we don't fully understand, could make fibromyalgia harder to spot for doctors accustomed to seeing mood problems in their female fibromyalgia patients.

Is Sleep More Important in Men?

A study published in 2012 in Psicothema looked at gender differences in the major fibromyalgia symptoms, including pain, sleep, fatigue, psychological disorders, emotional distress, and function.

 Researchers found that sleep quality was the best predictor of pain in men but not in women.

Fibromyalgia is known to involve sleep abnormalities and often overlaps with one or more sleep disorders along with unrefreshing sleep. This research suggests that identifying and treating sleep problems may be more important for men.

Understanding the Differences

So far, we don't have enough information to fully understand the differences in the male and female fibromyalgia experience. As we learn more, both about this condition and gender differences in general, we'll likely learn a lot more.

Until then, it's important to raise awareness that men can and do get fibromyalgia.

Sources:

Burnes LA, et. al. American Journal of Physiology. 2008 Apr;294(4):R1347-55 Enhanced muscle fatigue occurs in male but not female ASIC3-/- mice.

Jovanovic H, et. al. NeuroImage. 2008 Feb 1;39(3):1408-19. Sex differences in the serotonin 1A receptor and serotonin transporter binding in the human brain measured by PET.

Saxbe DE, Repetti RL, Nishina A. Health Psychology. 2008 Jan;27(1):15-25. Marital satisfaction, recovery from work, and diurnal cortisol among men and women.

Walderhaug E, et. al. Biological Psychiatry. 2007 Sep 15;62(6):593-9. Interactive effects of sex and 5-HTTLPR on mood and impulsivity during tryptophan depletion in healthy people.

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