TRT for Men: How Testosterone Replacement Therapy Affects Inflammation and Biological Age

Testosterone replacement therapy (TRT) is a medical treatment for testosterone deficiency in men, and its effects extend well beyond libido and muscle mass. Adequate testosterone levels regulate chronic inflammation, and chronic inflammation is the primary driver of biological aging. This inflammatory state can be tracked through glycans (complex sugars attached to Immunoglobulin G antibodies) that shift in response to hormonal and immune changes over time.

Hormones and biological age are more closely connected than most testing methods reveal. For a deeper look at how hormonal changes accelerate or slow immune aging, and how glycan biomarkers track that process, read our definitive guide: Menopause, HRT & Biological Age: The Definitive Guide to Tracking Hormonal Aging.

Does TRT actually lower biological age?

TRT can significantly reduce biological age in men with testosterone deficiency, as measured by GlycanAge. In a clinical trial involving 82 obese men with low testosterone, participants receiving testosterone therapy over 12 months showed statistically significant improvements across multiple glycan indexes, including increases in Glycan Shield and Glycan Youth (both anti-inflammatory markers) and a decrease in Glycan Mature (a pro-inflammatory marker), while the placebo group showed no meaningful change.

A cross-sectional study used as a validation cohort comprised 129 men in total, 66 of whom were on testosterone therapy, with a median age of 61 in the testosterone group. This arm showed the same directional pattern — lower agalactosylation and higher digalactosylation and sialylation compared with men on no treatment — confirming the findings from the clinical trial. When testosterone levels were optimized to the upper end of the normal range for a 25–35-year-old male, the reductions in GlycanAge were more pronounced.

How does testosterone reduce inflammation at the molecular level?

TRT's anti-inflammatory effect doesn't come from testosterone itself — it comes from estradiol, the estrogen that testosterone converts into through a process called aromatization. Researchers tested this by adding an aromatase inhibitor, a drug that blocks this conversion, to a TRT regimen. The result: the protective effect on glycan profiles disappeared. Men who couldn't convert testosterone into estradiol showed an increase in pro-inflammatory glycans instead, confirming that it's the estrogen derived from testosterone, not testosterone directly, that modulates IgG glycosylation.

This finding has direct clinical implications: TRT protocols that suppress estradiol conversion, through aggressive aromatase inhibitor use, may undermine the biological age benefits that TRT would otherwise produce.

"Men are protected from aging by testosterone — but only if aromatase, the enzyme that converts testosterone to estrogen, is not blocked. People taking testosterone often try to keep their levels high by blocking aromatase. If you do that, yes, you have high testosterone. But your GlycanAge is increasing, because you actually need estrogen."

— Prof. Gordan Lauc, Co-Founder and Chief Scientific Officer, GlycanAge

Which glycan indexes change with TRT, and what do they mean?

TRT in men with testosterone deficiency produces measurable improvements in three GlycanAge indexes:

Glycan Shield increases — reflecting a shift toward anti-inflammatory immune activity and greater immune resilience.

Glycan Youth increases — associated with a younger, less inflamed glycan profile.

Glycan Mature decreases — this index tracks agalactosylated glycans, a class of pro-inflammatory structures that accumulate with age and inflammaging. A reduction here is one of the clearest markers of a shift toward a less inflammatory glycan profile.

These changes are not cosmetic. They reflect a measurable shift in the ratio of pro-inflammatory to anti-inflammatory glycans — the same ratio that GlycanAge uses to calculate biological age.

Are GlycanAge results accurate for men currently on TRT?

GlycanAge results are accurate and clinically meaningful in men on TRT. Testosterone does not distort the test, but shapes the biology the test is measuring. In the first one to three months of therapy, results may reflect both baseline inflammation and early treatment effects; after several months on stable TRT, the result is more likely to represent the patient's new physiological steady state.

Well-managed TRT may support a more anti-inflammatory glycan profile, contributing to a younger biological age result. That said, responses are not uniformly favorable. Supraphysiological dosing and metabolic context both matter. GlycanAge can be used as a tool for tailoring individual treatment plans, since it responds to different types and administration methods of TRT.

How much can TRT reduce biological age in practice?

Case data from Raffaele Medical, a longevity clinic in New York City that has incorporated GlycanAge testing across hundreds of patients, shows reductions that go well beyond the population average. When Prof. Gordan Lauc's research team analysed the first cohort of samples from the clinic, discovered through a mutual connection, the results were striking: patients were returning GlycanAge scores 15, 20, and 30 years younger than their chronological age. The findings were compelling enough to prompt a direct collaboration between Lauc and Dr. Joseph Raffaele to understand what protocols were producing them.

The single largest result documented in that cohort was a 71-year-old male with a GlycanAge of 20 — a difference of 51 years. Across the broader patient population at the clinic, the average reduction has been described as 25 years, a figure Dr. Raffaele attributes to the cumulative effect of hormone optimisation combined with the metabolic and lifestyle protocols applied throughout the programme. Most of these results come from patients who had been on protocol for at least one year, and in many cases five to ten years, suggesting the glycan response to optimised TRT compounds over time rather than plateauing after the first retest.

Does metformin add to TRT's anti-inflammatory effects on glycans?

Metformin does not meaningfully enhance the glycan improvements produced by TRT. In the 12-month clinical trial of 82 men, the metformin group showed no statistically significant changes in IgG glycans, and combining metformin with TRT produced results essentially identical to TRT alone, indicating that the testosterone effect was the primary driver. One individual in the metformin group showed an outlier response, but this did not reach statistical significance at the group level.

How often should men on TRT retest with GlycanAge?

GlycanAge responds to meaningful biological change within 3–4 months of a targeted intervention, making it well-suited to TRT monitoring. A baseline test before initiating therapy establishes the starting point; a follow-up test at 6–12 months captures the glycan response once hormone levels have stabilised. For men whose protocols are being adjusted, particularly those whose estradiol management is being refined, retesting at each significant protocol change provides objective data on whether the adjustment is producing the intended anti-inflammatory effect.

Because GlycanAge measures the cumulative inflammatory state rather than acute hormonal fluctuations, it filters out the day-to-day variability that makes standard blood panels difficult to interpret longitudinally.

"What I love about the GlycanAge test is that you can see changes within three months, and they're quite stable. The changes occur quickly — you can see them, you can monitor what you're doing, and alter your therapy if you need to."

— Dr. Joseph Raffaele, Raffaele Medical, New York

If you are on TRT or evaluating hormone optimisation and want to measure its effect on your biological age, a GlycanAge test gives you a direct read on how your immune system is responding — not a proxy, not a genetic estimate, but the active inflammatory biology that determines how fast you are aging.

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