Total testosterone — necessary, not sufficient
Total testosterone is the headline number, and it is the least useful one read alone. The population reference runs roughly 264–916 ng/dL; the functional target for a man who wants drive, recovery, and body composition sits in the upper half, ~600–900 ng/dL. But total testosterone counts every molecule in the blood, including the large fraction bound up and biologically inert. Two men with an identical total of 700 ng/dL can feel completely different depending on how much of it is free. Draw it in the morning — testosterone has a diurnal rhythm and an afternoon value reads falsely low. On injectable testosterone, draw at trough (just before the next dose) and judge against symptoms, never against a single peak.
Free testosterone — and the assay trap that ruins it
Free testosterone is the unbound fraction that actually crosses cell membranes and binds the receptor — the number that best tracks how a man feels. It is also the marker most often misread, because the assay matters enormously.
By the accurate method — equilibrium dialysis or a calculated (Vermeulen) free T — the adult-male range is roughly 35–155 pg/mL, and optimized men tend to feel best in the upper band, ~100–150 pg/mL (≈10–15 ng/dL). The cheaper direct analog immunoassay systematically underestimates free T by about fourfold and reads ~6–26 pg/mL. These are not two opinions about the same range — they are two different machines, and their numbers must never be compared. If your free T looks implausibly low, check whether the lab ran the direct assay, and if it matters, insist on equilibrium dialysis or a calculated value.
SHBG — the gatekeeper
Sex hormone-binding globulin decides how much of your total testosterone is actually available. The optimal band is ~25–45 nmol/L. High SHBG sequesters testosterone and can leave a man symptomatic at a "normal" total. Low SHBG frees more testosterone but shortens its apparent half-life and is one of the earliest, most sensitive signals of insulin resistance — it often falls before glucose or insulin move. Always read total testosterone through SHBG.
Estradiol — manage it, never crush it
In men, estradiol is protective — for bone, joints, lipids, libido, and mood. Use the sensitive (LC-MS/MS) assay; the standard female-calibrated immunoassay reads garbage at male levels. The functional band is ~20–35 pg/mL, with concern above ~50. The most common self-inflicted error in this entire panel is crushing estradiol with aromatase inhibitors: the result is joint pain, flat mood, dead libido, poor lipids, and bone loss. The goal is management, not eradication.
LH and FSH — the signal from upstream
Luteinizing hormone and follicle-stimulating hormone are the pituitary's instructions to the testes. In a natural man they confirm whether low testosterone is a testicular problem (high LH/FSH — the brain is shouting but the testes can't answer) or a signaling problem (low LH/FSH). On any exogenous androgen they are expected to be suppressed to near zero — that is the feedback loop working, not a disease. They become informative again only during a restart or fertility protocol.
Prolactin and DHEA-S
Prolactin sits quietly until it doesn't: markedly elevated values suppress the whole axis and blunt libido, and warrant a repeat draw (it spikes with stress and recent activity) before any imaging workup. The 19-nortestosterone family of compounds raises it. DHEA-S is an adrenal androgen precursor that is strongly age-banded — what's normal at 25 (~280–640 µg/dL) is high at 60 (~28–175). Read it against your age decade, target the upper third of that band, and don't compare it to a single all-ages range.
Reading the panel together
No hormone marker means anything alone. Total without free and SHBG is a guess. Free T without the assay method is a coin flip. Estradiol without the sensitive assay is noise. LH and FSH on a protocol are expected to be floored, not alarming. The discipline is to read the panel as one connected system, draw it under standardized conditions (morning, fasted where relevant, trough on TRT), and trend it — not to react to one number on one morning.
Educational only; not medical or dosing advice.