Testosterone consistently behaves as an anti-inflammatory hormone when circulating at normal physiological levels, reducing key inflammatory signals and shifting the immune system toward a calmer baseline. But calling it simply “anti-inflammatory” flattens a genuinely complicated picture. In certain tissues and at certain doses, testosterone can actually amplify inflammation, and some of its calming effects turn out to work only after the body converts it into estrogen. The relationship between testosterone and inflammation is real, well-documented, and far more interesting than a simple yes-or-no label suggests.
What Happens to Inflammatory Signals When Testosterone Rises
The most consistent finding across human and cell studies is that testosterone dials down a cluster of pro-inflammatory molecules while boosting at least one anti-inflammatory one. In men with low testosterone who receive replacement therapy, researchers reliably see drops in tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and sometimes IL-6, all of which are chemical messengers that drive inflammation. At the same time, the anti-inflammatory messenger IL-10 tends to rise. A controlled crossover trial in 27 older men with androgen deficiency found that testosterone replacement reduced TNF-α and raised IL-10 compared with placebo, shifting the overall cytokine balance toward less inflammation.1The Journal of Clinical Endocrinology & Metabolism. The Effect of Testosterone Replacement on Endogenous Inflammatory Cytokines and Lipid Profiles in Hypogonadal Men This pattern has been observed across men with coronary artery disease, prostate cancer, and diabetes.2PubMed. The relationship between circulating testosterone and inflammatory cytokines in men
Looking at the broader evidence, testosterone also inhibits C-reactive protein (CRP), a blood marker that doctors routinely check to gauge systemic inflammation.3PubMed Central. Do Androgens Modulate the Pathophysiological Pathways of Inflammation? Appraising the Contemporary Evidence In men with metabolic syndrome, a double-blinded placebo-controlled trial (the Moscow Study) confirmed that testosterone supplementation lowered IL-1β, TNF-α, and CRP, though IL-6 and IL-10 did not change in that particular cohort.4PubMed. Effects of testosterone supplementation on markers of the metabolic syndrome and inflammation in hypogonadal men with the metabolic syndrome: the double-blinded placebo-controlled Moscow study The slight inconsistencies between trials, where some cytokines move and others stay flat, probably reflect differences in the men studied and the testosterone formulations used. But the overall direction is strikingly consistent: physiological testosterone pushes the inflammatory dial down.
How Testosterone Talks to the Immune System
Testosterone does not just passively float through the bloodstream and happen to correlate with lower inflammation. It actively reshapes how immune cells behave in at least two important ways.
The first involves regulatory T cells, a specialized subset of white blood cells that act as the immune system’s brakes. These cells prevent the immune response from attacking the body’s own tissues. When men are chemically castrated (their testosterone is suppressed with medication), the proportion of regulatory T cells drops, and when testosterone is restored back to normal, those cells recover.5PubMed. Effect of medical castration on CD4+ CD25+ T cells, CD8+ T cell IFN-gamma expression, and NK cells: a physiological role for testosterone and/or its metabolites In rat models of autoimmune inflammation, testosterone replacement expanded the regulatory T cell population and reduced the accumulation of inflammatory macrophages.6The Journal of Immunology. Testosterone Replacement Effectively Inhibits the Development of Experimental Autoimmune Orchitis in Rats: Evidence for a Direct Role of Testosterone on Regulatory T Cell Expansion Researchers have even identified a specific site within the gene for Foxp3, the master switch protein of regulatory T cells, where androgen receptors bind and increase its expression.7PubMed Central. Androgen receptor modulates Foxp3 expression in CD4+CD25+Foxp3+ regulatory T-cells So testosterone doesn’t just dampen inflammation indirectly; it literally helps build the cellular infrastructure that keeps immune overreaction in check.
The second mechanism involves macrophages, the immune cells that swallow pathogens and debris. Macrophages can be broadly polarized into pro-inflammatory states or tissue-repair states. Cell culture work shows that pre-treating macrophages with testosterone enhanced their anti-inflammatory gene expression and reduced their production of IL-1β.8PubMed Central. Investigating the Effects of Sex Hormones on Macrophage Polarization In a mouse model of allergic lung inflammation, androgen-receptor activation promoted the tissue-repair macrophage phenotype, and knocking out androgen receptors in airway macrophages impaired this polarization.9PubMed Central. Androgen and androgen receptor as enhancers of M2 macrophage polarization in allergic lung inflammation Interestingly, the researchers who conducted that lung study expected androgens to suppress this anti-inflammatory macrophage state, not promote it. The result was the opposite of their hypothesis.
One Key Pathway Testosterone Uses to Calm Inflammation
At the molecular level, one of the most important things testosterone does is suppress a protein complex called NF-κB, which is essentially a master switch for inflammatory gene expression. When NF-κB is activated, cells ramp up production of inflammatory cytokines, adhesion molecules, and other factors that drive tissue damage. Testosterone at physiological concentrations significantly reduces NF-κB’s ability to bind DNA and activate those genes.10PubMed Central. Testosterone alleviates tumor necrosis factor-alpha-mediated tissue factor pathway inhibitor downregulation via suppression of nuclear factor-kappa B in endothelial cells This helps explain why the effects of testosterone show up across so many different cell types and tissues: NF-κB is active almost everywhere in the body, and dampening it is a broad-spectrum anti-inflammatory move.
The Aromatase Twist
Here is where the story gets genuinely surprising. Some of testosterone’s anti-inflammatory effects don’t come from testosterone itself but from estradiol, the estrogen it gets converted into by an enzyme called aromatase. Blood vessels contain aromatase, and when testosterone encounters it in endothelial cells lining arteries, it gets transformed into estradiol. In that form, it reduces the expression of adhesion molecules like VCAM-1, which are proteins that attract white blood cells to artery walls and fuel the development of atherosclerotic plaques. When researchers blocked aromatase, testosterone’s ability to suppress these adhesion molecules was abolished.11PubMed Central. Testosterone attenuates expression of vascular cell adhesion molecule-1 by conversion to estradiol by aromatase in endothelial cells: implications in atherosclerosis
This matters for two reasons. First, it means that testosterone’s cardiovascular protection may partly depend on healthy aromatase activity. Second, it helps explain why dihydrotestosterone (DHT), a potent androgen that cannot be converted to estradiol, does not share all of testosterone’s anti-inflammatory effects in blood vessels. A broader review of testosterone’s anti-inflammatory mechanisms notes that after aromatization, the resulting estradiol activates estrogen receptors in fat tissue to decrease the release of inflammatory adipokines like leptin, IL-6, and TNF-α.12Journal of the Endocrine Society. The Anti-Inflammatory Effects of Testosterone
Not every study agrees on the vascular picture, though. At least one lab experiment found that testosterone transiently increased TNF-α-induced expression of adhesion molecules in endothelial cells rather than suppressing them, suggesting the timing and concentration of exposure matter a great deal.13PubMed. Testosterone and estradiol modulate TNF-alpha-induced expression of adhesion molecules in endothelial cells The discrepancy likely reflects differences in experimental design, but it is a reminder that not every testosterone effect points in the same anti-inflammatory direction.
The Fat Connection
Testosterone’s relationship with body fat creates one of the clearest feedback loops between the hormone and inflammation. Low testosterone promotes fat accumulation, and fat tissue is a factory for inflammatory molecules. Adipose tissue releases TNF-α, IL-6, leptin, and other signals that sustain chronic low-grade inflammation. Testosterone inhibits fat expansion, reduces the size of individual fat cells, and dials back the production of these inflammatory adipokines while boosting adiponectin, a protein with anti-inflammatory and insulin-sensitizing properties.12Journal of the Endocrine Society. The Anti-Inflammatory Effects of Testosterone A meta-analysis of testosterone replacement in men with type 2 diabetes or metabolic syndrome concluded that suppression of the inflammatory state may be one mechanism by which testosterone improves insulin sensitivity.14PubMed Central. Metabolic Effects of Testosterone Replacement Therapy in Patients with Type 2 Diabetes Mellitus or Metabolic Syndrome: A Meta-Analysis
The loop also runs in the other direction. Obesity itself can suppress testosterone production. In prepubertal boys, inflamed fat tissue near the testes promotes an enzyme pathway that converts local androgens into estrogen, effectively undermining testicular function.15PubMed. Obesity impairs male reproductive development in prepubertal boys via local adipose tissue inflammation and the STAT3/CYP19A1 pathway So fat drives inflammation, inflammation lowers testosterone, and lower testosterone encourages more fat. Breaking that cycle is one of the practical reasons clinicians consider testosterone therapy in obese, hypogonadal men.
The Wound Healing Paradox
If testosterone is broadly anti-inflammatory, you might expect it to help wounds heal smoothly. It does the opposite. In skin wound healing, testosterone actually promotes a stronger inflammatory response and slows the repair process. Castrated male mice heal cutaneous wounds dramatically faster than intact males, and the acceleration is associated with reduced local inflammation.16PubMed Central. Androgen receptor-mediated inhibition of cutaneous wound healing Human studies confirmed the pattern: men with higher endogenous testosterone show an enhanced inflammatory response at wound sites and slower healing.17PubMed. Influence of physiological androgen levels on wound healing and immune status in men
The mechanism appears to involve testosterone directly increasing pro-inflammatory cytokine expression by macrophages at the wound site. Mouse models in which androgen receptors were knocked out specifically in myeloid cells (the immune cell lineage that includes macrophages) showed rescued wound healing because the TNF-driven inflammatory response was no longer amplified.18PubMed Central. The testosterone paradox of advanced prostate cancer: mechanistic insights and clinical implications This is a genuine paradox: the same hormone that systemically lowers inflammatory cytokines in the bloodstream cranks up local inflammation in healing skin. The difference seems to be context. In adipose tissue and circulating immune cells, testosterone calms things down. In wound-site macrophages, androgen receptor activation revs up TNF-α production. Tissue type and local conditions determine which face of testosterone the immune system sees.
When the Dose Goes Wrong
Everything discussed so far applies to testosterone at physiological levels, the concentrations a healthy body produces or that are restored through standard replacement therapy. Supraphysiological doses, the kind used in anabolic steroid abuse, tell a different story. At high doses, anabolic-androgenic steroids promote systemic inflammation by increasing the very cytokines that normal testosterone suppresses: IL-6 and TNF-α, along with endothelial adhesion molecules like VCAM-1 and ICAM-1 that recruit white blood cells to artery walls.19The Journal of Steroid Biochemistry and Molecular Biology. Anabolic-androgenic steroids at supraphysiological doses: Cardiovascular impacts and pathophysiological mechanisms Excessive androgen receptor signaling at these doses can directly activate pro-inflammatory genes. The result is a reversal: what protects at normal levels contributes to cardiovascular damage at abusive doses. This distinction between physiological and supraphysiological effects is one of the most practically important things to understand about testosterone and inflammation.
Protection Against Brain Inflammation
Testosterone’s anti-inflammatory reach extends into the central nervous system. In the brain, the resident immune cells are microglia and astrocytes. After a brain injury in male rats, both early and delayed administration of testosterone significantly reduced reactive microglia and reactive astrocytes, the cellular signatures of neuroinflammation. Both of testosterone’s major metabolites, estradiol and DHT, appeared to contribute, with estradiol mediating part of the effect across both time windows and DHT contributing to the early microglial response.20PubMed. Testosterone decreases reactive astroglia and reactive microglia after brain injury in male rats: role of its metabolites, oestradiol and dihydrotestosterone
More recently, researchers have found that testosterone enhances the ability of microglia to clear amyloid-beta, the protein fragment that accumulates in Alzheimer’s disease. Testosterone promotes autophagy in microglia, essentially turbocharging their self-cleaning machinery, through a receptor pathway that suppresses a pro-growth signal and allows the cellular recycling process to proceed.21PubMed Central. Role of Testosterone Signaling in Microglia: A Potential Role for Sex‐Related Differences in Alzheimer’s Disease This finding has implications for understanding why men and women differ in Alzheimer’s risk trajectories, particularly as men’s testosterone levels decline with age.
Why Women Get More Autoimmune Diseases
One of the most striking real-world consequences of testosterone’s immunosuppressive properties is the sex gap in autoimmune disease. Women are far more likely than men to develop conditions like lupus, rheumatoid arthritis, multiple sclerosis, and Hashimoto’s thyroiditis. While many factors contribute to this disparity, the hormonal influence is firmly established. Sex hormones modulate lymphocyte behavior at every stage of life, from prenatal development through adulthood.22PubMed Central. Sex hormones, immune responses, and autoimmune diseases. Mechanisms of sex hormone action. Testosterone’s expansion of regulatory T cells and its suppression of pro-inflammatory cytokines both help explain why men’s immune systems are less likely to turn on their own tissues. The trade-off is that the same dampening makes men somewhat more susceptible to certain infections and potentially less responsive to some vaccines, an observation that has been documented repeatedly in immunology research.
What Happens During Critical Illness
When the body faces severe acute stress, like sepsis, major trauma, or critical illness requiring intensive care, testosterone levels collapse. The drop begins on the first day, reaches its lowest point around day three, and can take up to two months to recover.23PubMed Central. A review of the role of testosterone in the care of the critically ill patient This plunge removes one of the body’s endogenous brakes on inflammation at precisely the moment when inflammatory signals are surging. Whether administering testosterone during critical illness would be beneficial or harmful remains an open question. The inflammatory surge in sepsis serves a purpose, fighting infection, so dampening it with exogenous testosterone could theoretically interfere with host defense. Clinical trials in this space are scarce, and the topic remains one of the more challenging frontiers in critical care endocrinology.
Aging, Declining Testosterone, and Chronic Inflammation
As men age, testosterone levels gradually decline while markers of chronic, low-grade inflammation creep upward, a process sometimes called “inflammaging.” These two trends are not a coincidence. The decline in testosterone removes its restraint on pro-inflammatory cytokines and adipose-tissue-derived inflammatory molecules, while age-related fat gain further feeds the cycle.24Anti-Aging Eastern Europe. MEN’S HEALTH IN AUTOIMMUNE RHEUMATIC DISEASES: AGING, IMMUNITY, AND HORMONAL INTERACTIONS In men with autoimmune rheumatic diseases, this combination of hormonal decline and inflammaging is thought to amplify disease burden.
There is even an evolutionary lens on this. In a study of red-legged partridges, middle-aged males given extra testosterone were able to increase their sexual signaling (carotenoid-based coloring) without a measurable hit to their cell-mediated immunity. Old males given the same testosterone boost could not increase their signaling and showed clear immunosuppression.25PubMed Central. Testosterone-mediated trade-offs in the old age: a new approach to the immunocompetence handicap and carotenoid-based sexual signalling. The finding suggests that the cost of testosterone on the immune system depends on the organism’s overall physiological reserves, and that aging narrows the window in which testosterone can be immunomodulatory without being immunosuppressive. Whether this maps directly onto human aging is uncertain, but it fits the pattern clinicians observe: testosterone therapy in younger hypogonadal men tends to improve inflammatory markers, while the risk-benefit calculation in very old men with multiple comorbidities is harder to call.