The nine biomarkers that actually matter.

Total testosterone measures every molecule of testosterone in your blood — the active portion, the portion bound to albumin, and the portion bound tightly to SHBG that your body can't use. A reading inside the lab range tells you almost nothing on its own. A 47-year-old at 320 ng/dL is "normal" by the lab's standard and miserable in his own body.

Total testosterone matters most as the starting point for everything else. Free testosterone, SHBG, and estradiol all need this number to make sense.

Free testosterone is the portion of total testosterone that's bioavailable — not bound to SHBG, free to enter cells and do work. This is the number that correlates with how you actually feel. Libido, energy, recovery, motivation. A man with high total T and low free T will still feel symptomatic.

Most labs calculate free T from total T and SHBG (a calculation called "calculated free T"). A few labs measure it directly. The calculated version is fine for tracking trends in yourself; the direct measure is more accurate cross-lab.

SHBG is the protein that binds testosterone in your blood and renders it inactive. The higher your SHBG, the more of your testosterone is locked up and unavailable. This is the biomarker that almost no doctor orders and almost no man knows about — and it's the single most useful number for explaining why your free testosterone won't budge.

High SHBG (above 50) often correlates with thyroid issues, low body fat with high training volume, chronic alcohol intake, or aging. Low SHBG (below 20) often correlates with insulin resistance, fatty liver, or excess body fat.

If you're working on hormonal optimization, this is the lever most men have never pulled. Read the full SHBG protocol →

DHT is the metabolite of testosterone, converted by the enzyme 5-alpha reductase. It's roughly three times more potent than testosterone at the androgen receptor. DHT drives libido, erectile function, body and facial hair, and — at high levels — pattern hair loss and prostate growth.

Most men either ignore DHT entirely or assume "lower is better" because of hair loss concerns. Both are wrong. Sexual function and tissue health depend on adequate DHT. Men on aggressive 5-AR inhibitors (finasteride, dutasteride) for hair loss frequently report ED, anhedonia, and post-finasteride syndrome — the DHT was doing something important.

LH is the pituitary hormone that signals your testes to produce testosterone. It's the diagnostic that tells you whether low testosterone is a signaling problem (low LH = the brain isn't asking) or a production problem (high LH = the brain is shouting and the testes aren't responding).

Men with low T and low LH have secondary hypogonadism — the pituitary signal is the bottleneck. Men with low T and high LH have primary hypogonadism — the testes themselves can't produce enough. The treatment paths diverge entirely. Without LH, you don't know which one you have.

FSH is the pituitary hormone that drives sperm production. For men interested in fertility — or men on exogenous testosterone who plan to come off — this is the marker that tells you whether testicular function is intact. Suppressed FSH and LH together with low T (often from prior steroid use, illness, or extended TRT) is the signature of HPG axis shutdown.

FSH is the single most important marker if fertility matters to you. Men starting TRT should always get a baseline FSH before they begin.

Estradiol is not a "female hormone" — men need it. It's protective for bone density, cardiovascular health, libido, and erectile function. The mistake most TRT clinics make is treating estradiol as something to crush with aromatase inhibitors. Too-low E2 produces joint pain, low libido, depression, and accelerated bone loss.

Two important notes. First, insist on the sensitive estradiol assay — the standard test is calibrated for women and unreliable in the male range. Second, E2 only makes sense in the context of total testosterone. The ratio matters more than the absolute number.

rMSSD is the root mean square of successive heart-rate differences — the most stable HRV metric for tracking parasympathetic recovery. Unlike the other markers on this page, you don't need a blood draw. A Whoop, Oura, Garmin, or a chest strap with a free app will give you a nightly reading.

What rMSSD tells you: how your nervous system is handling load. A trend down over weeks signals you're not recovering — from training, work stress, sleep debt, or a brewing infection. A trend up signals you're adapting. The number itself matters less than the seven-day rolling average against your own baseline.

This is the only biomarker on the list you can move with sleep, breathwork, and stress management in a single week.

hsCRP is a sensitive marker of systemic inflammation. It rises with infection, injury, visceral fat accumulation, poor sleep, periodontal disease, and cardiovascular risk. The lab calls anything under 3.0 normal. Optimization-minded research consistently associates below 1.0 with lower long-term cardiovascular and all-cause mortality risk.

hsCRP is the one inflammation marker that's cheap, available everywhere, and responsive to lifestyle. If yours is above 1.0, the usual suspects are visceral fat, sleep fragmentation, low-grade gum infection, or a chronic stress load that isn't being managed.