The Truth About TRT: Why Your T Level Isn't the Whole Picture

Most men who get their testosterone checked walk out of the clinic with a single number and a verdict. Above 300 nanograms per deciliter and you're "normal." Below it and maybe you qualify for treatment. That number becomes the entire conversation, the entire decision, and often the entire reason someone either gets help or gets told to go home. But the testosterone level is just one piece of the picture, and treating it as the whole picture is where a lot of men end up stuck, feeling terrible with labs that look "fine."

To understand why, you need to understand the system that testosterone operates within, because testosterone doesn't work in isolation. It's produced through a chain that starts in the brain, specifically the hypothalamus, which sends a signal called GnRH to the pituitary gland, which then releases two hormones called LH and FSH, which travel to the testes and trigger testosterone production. That testosterone then circulates through the blood, binds to androgen receptors in muscle, bone, brain, and other tissues, and exerts its effects. But how much of it is free versus bound to proteins like SHBG, how sensitive your receptors are, how well your liver clears metabolites, how your cardiovascular system handles the downstream metabolic changes, all of that determines what that testosterone number actually means for you as a person. Two men with the exact same serum testosterone can feel completely different, perform completely different, and carry completely different health risks.

That's the context you need before the rest of this makes sense.

If I have a patient who comes in and his testosterone level is 450 and he's legitimately tired all the time, brain fog, trouble sleeping, not feeling like he's getting the recovery, like all the telltale signs of low testosterone, maybe for that guy, 450 isn't enough. This is the part most conventional medical models miss. The reference ranges on lab work are population based, meaning they reflect the statistical distribution of values across thousands of men of varying ages, health statuses, and genetics. A level of 450 sits comfortably in the "normal" range on almost every lab panel in the country. But normal for a population doesn't mean optimal for an individual, and the gap between those two ideas is where a lot of suffering lives.

Consider shoe sizes as a way of understanding this, because the average men's shoe size in the United States is somewhere around a 10.5, which is the statistical middle of the population distribution but tells you nothing about what any individual man actually needs, so if you're a size 13 and someone hands you a 10.5, your feet technically have shoes on them but you can't move through the world the way you're supposed to, and testosterone works exactly the same way because some men feel completely functional at 450 while others need closer to 700 before they recognize themselves again, and the number sitting on the lab report doesn't tell you which category a given person falls into or whether the hormone is actually doing its job in the tissues where it matters.

This is partly because of something called androgen receptor density, which varies from person to person and determines how effectively your cells respond to the testosterone that reaches them. A man with high receptor density might thrive at a lower serum level because his tissues are pulling in and using the hormone efficiently. A man with lower receptor density might need more circulating testosterone to achieve the same cellular effect. We don't routinely measure receptor sensitivity in clinical practice, which means the serum number is always an incomplete proxy for what's actually happening at the tissue level.

And then there's SHBG, or sex hormone binding globulin, a protein made by the liver that binds to testosterone in the blood and renders it inactive. If your SHBG is high, a larger percentage of your total testosterone is locked up and unavailable. You could have a total testosterone of 600 but a free testosterone, which is the fraction actually available to your cells, that's sitting in the basement. This is another reason why looking at a single total testosterone number and making a binary decision from it misses the point entirely.

So if the number alone isn't enough, what should the decision be based on? This is where the approach shifts from a single lab value to a full systems evaluation. How do you feel? How are you performing? Is your recovery better? Is your brain fog gone? Is your performance what it should be? Do you have good memory? Are you sleeping well? How's your sexual performance? What is your GGT? What is your cystatin C? What's your HSCRP? What are your blood lipids at? What's your APOB, right? These are the things that I care about when we're talking about liver, kidney, heart, cardiovascular health, or what's your blood pressure at? Are you healthy there? How are you sleeping? How are you recovering? How do you feel mentally? How is your memory? We would be looking at the full picture when it comes to our labs and making a decision based upon your holistic health rather than just looking at the TRT number.

Each of those markers tells a different part of the story, and they become especially important when you're considering testosterone replacement therapy because TRT doesn't just affect how you feel. It changes metabolic parameters across multiple organ systems, and monitoring those changes is how you ensure the intervention is actually making someone healthier rather than just making their testosterone number higher.

GGT, or gamma glutamyl transferase, is a liver enzyme that acts as an early warning signal for liver stress. It's sensitive to changes in how the liver processes hormones and medications, so when you introduce exogenous testosterone, watching GGT helps you know whether the liver is handling the increased metabolic load without strain. Cystatin C is a marker of kidney function that's more precise than the traditional creatinine measure many doctors rely on, because it's less affected by muscle mass, which matters a lot when you're dealing with men who are training hard and carrying more lean tissue. An elevated cystatin C on TRT might signal that kidney filtration is being affected in a way that creatinine alone wouldn't catch.

HSCRP, or high sensitivity C reactive protein, measures systemic inflammation. This one matters because the relationship between testosterone and cardiovascular health has been debated for decades. Morgentaler and colleagues, writing in Postgraduate Medicine in 2015, reviewed the evidence and found that the historical fear of testosterone causing heart disease was largely based on misinterpreted data and a few flawed studies, and that low testosterone itself is actually associated with increased cardiovascular risk, higher rates of metabolic syndrome, and greater mortality. But that doesn't mean you can just push testosterone levels up and assume the heart is fine. You have to watch the inflammatory markers that tell you whether the cardiovascular system is actually in a good place, which is exactly what HSCRP does.

APOB, or apolipoprotein B, is arguably the most important cardiovascular risk marker most people have never heard of. Each APOB molecule represents one atherogenic lipoprotein particle, so it gives you a direct count of the particles capable of penetrating your arterial walls and forming plaque. Standard lipid panels show LDL cholesterol, which estimates the cholesterol carried within those particles, but two men with the same LDL cholesterol can have very different particle counts, and it's the particle count that drives risk. Work by Wagner and colleagues, published in Arteriosclerosis, Thrombosis, and Vascular Biology in 1996, showed that testosterone can alter arterial LDL metabolism in meaningful ways, which makes tracking APOB on TRT a direct window into whether the therapy is shifting cardiovascular risk in the wrong direction. If your APOB stays low and your HSCRP stays low while you're on testosterone, that's real evidence your heart is handling the therapy well. If either starts climbing, that's actionable information you wouldn't get from your testosterone level alone.

Tracking blood pressure belongs in that same conversation, because testosterone can increase red blood cell production through a process called erythrocytosis, which thickens the blood and can raise blood pressure and increase the risk of clotting events, and this is one of the most well documented side effects of TRT and the reason why hematocrit, the percentage of your blood volume occupied by red blood cells, should be monitored regularly. A man whose blood pressure creeps up on TRT isn't necessarily having a bad response to testosterone. He might just need a dose adjustment, or he might need to donate blood to bring his hematocrit down. But you can only know that if you're looking at the full picture.

Sleep is in that list of questions for a reason that goes beyond comfort. Testosterone is primarily produced during sleep, with the largest pulses occurring during deep sleep stages. Poor sleep suppresses LH release from the pituitary, which directly lowers testosterone production. So if a man starts TRT and his sleep doesn't improve, or gets worse, something is being missed. Sleep apnea in particular has a complex relationship with testosterone because TRT can worsen existing sleep apnea in some men, which in turn undermines recovery, cognitive function, and the very symptoms that led to seeking treatment in the first place. Monitoring sleep quality and screening for apnea becomes part of the feedback loop that tells you whether the therapy is truly working.

The practical takeaway from all of this is that the conversation around TRT should never begin and end with "what's your testosterone at." The starting point is symptoms, the middle is a comprehensive lab panel that includes liver, kidney, cardiovascular, and inflammatory markers, and the endpoint is not a number but a state of health. Are you recovering well? Is your cognition sharp? Is your cardiovascular risk profile stable or improving? Are your organs handling the therapy without strain? Those are the questions that determine whether TRT is working, not whether your serum testosterone crossed some arbitrary line on a lab report.

We would be looking at the full picture when it comes to our labs and making a decision based upon your holistic health rather than just looking at the TRT number. That sentence reframes the entire relationship most men have with testosterone. The number is the beginning of the conversation. The body's response to that number, across every system it touches, is the conversation itself.

References:

Javed Z, Papageorgiou M, Deshmukh H et al.. A Randomized, Controlled Trial of Vitamin D Supplementation on Cardiovascular Risk Factors, Hormones, and Liver Markers in Women with Polycystic Ovary Syndrome. Nutrients. 2019. https://pubmed.ncbi.nlm.nih.gov/30658483/

Barrea L, Muscogiuri G, Pugliese G et al.. Metabolically Healthy Obesity (MHO) vs. Metabolically Unhealthy Obesity (MUO) Phenotypes in PCOS: Association with Endocrine-Metabolic Profile, Adherence to the Mediterranean Diet, and Body Composition. Nutrients. 2021. https://pubmed.ncbi.nlm.nih.gov/34836180/

Morgentaler A, Feibus A, Baum N. Testosterone and cardiovascular disease--the controversy and the facts. Postgrad Med. 2015. https://pubmed.ncbi.nlm.nih.gov/25708023/

Wagner JD, Zhang L, Williams JK et al.. Esterified estrogens with and without methyltestosterone decrease arterial LDL metabolism in cynomolgus monkeys. Arterioscler Thromb Vasc Biol. 1996. https://pubmed.ncbi.nlm.nih.gov/8977451/