Baseline Labs Before Starting TRT: The Pre-Treatment Panel, Explained

Testosterone therapy is a long-term commitment with a short list of real risks — thickened blood, prostate effects, suppressed fertility, worsened sleep apnea, and the cardiovascular questions the TRAVERSE trial addressed — and every one of them is managed by comparing later numbers to the ones taken before the first dose. A baseline drawn properly also answers the question clinics skip too often: is testosterone actually low, and if so, why? A third of men with a single low reading test normal on repeat, and a low testosterone with low LH points to the pituitary, not the testes, which changes the work-up entirely.

Both major US guidelines — the Endocrine Society (2018) and the American Urological Association (2018) — agree on the skeleton: two separate fasting morning total testosterone measurements, free testosterone when binding protein could mislead, LH and FSH to locate the problem, and a safety baseline of hematocrit, PSA and metabolic markers. The sections below walk through that panel in the order a careful clinician reads it.

Testosterone peaks in the early morning and falls through the day, by 20–30% in younger men; it also drops after poor sleep, acute illness, fasting beyond a day, heavy training and glucocorticoids. So the diagnostic sample is drawn between 7 and 10 am, fasting, on an ordinary day, and a low result is repeated on a second morning before any diagnosis is made. The AUA uses 300 ng/dL as the cut-point; the Endocrine Society uses the harmonized lower limit of about 264 ng/dL for a CDC-standardized assay. A level in the 300s with symptoms is a gray zone where free testosterone decides.

Ask for a method that is standardized — LC/MS-MS is the reference — and use the same laboratory for the repeat; immunoassays from different labs can disagree by 10–15%.

Only 1–3% of testosterone circulates free; the rest is bound to SHBG (tightly) and albumin (loosely). SHBG rises with age, liver disease, hyperthyroidism, HIV therapy and anticonvulsants and falls with obesity, insulin resistance, hypothyroidism and nephrotic syndrome — so an obese man can have a "low" total with a normal free level (not deficient), and an older lean man a "normal" total with a low free level (deficient). Measure free testosterone when total is borderline (roughly 200–400 ng/dL) or SHBG is likely abnormal. Calculated free testosterone from total, SHBG and albumin (the Vermeulen equation) or an equilibrium-dialysis measurement are the trusted methods; the direct analog free-T immunoassay is not, and guidelines say so.

Once low testosterone is confirmed, LH and FSH say where the fault lies. High LH and FSH with low testosterone is primary hypogonadism — the testes themselves (Klinefelter syndrome, prior chemotherapy or radiation, mumps orchitis, trauma, aging). Low or inappropriately normal LH and FSH is secondary hypogonadism — the pituitary or hypothalamus is not signalling (obesity and metabolic disease, opioids, anabolic steroid use, sleep apnea, hemochromatosis, a pituitary tumor, head injury). The distinction matters because secondary causes are often reversible, and because a man who wants children should not be put straight on testosterone — it switches off sperm production — when clomiphene or gonadotropins would treat the cause and preserve fertility.

Prolactin is checked when LH is low or testosterone is very low (below about 150 ng/dL): a prolactin-secreting pituitary tumor is one of the few causes of hypogonadism that is treated with a pill rather than testosterone, and a markedly raised prolactin leads to pituitary imaging. Iron studies (ferritin, transferrin saturation) belong here too when secondary hypogonadism is unexplained, because hemochromatosis damages the pituitary.

CBC with hematocrit. Testosterone stimulates red cell production; erythrocytosis is the most common reason therapy is reduced or paused. Guidelines advise not starting above a hematocrit of 50% and holding or reducing at 54%. A high baseline hematocrit also raises the question of undiagnosed sleep apnea or smoking, both of which should be addressed first.

PSA (men 40 and over; earlier with family history or African ancestry). Testosterone does not cause prostate cancer, but it can accelerate one that is present, so a baseline PSA and digital rectal exam are standard. The Endocrine Society advises urology evaluation before starting if PSA is above 4 ng/mL, or above 3 with higher-risk background, and on therapy if PSA rises by more than 1.4 ng/mL in a year or above 4.

Lipid panel, HbA1c or fasting glucose, and a comprehensive metabolic panel. Testosterone therapy modestly lowers HDL in some men and changes body composition and insulin sensitivity; liver enzymes matter for oral and some injectable formulations and because fatty liver and alcohol both lower testosterone. These baselines let you see what therapy changed rather than what was already there.

Estradiol. Some of every testosterone dose is converted to estradiol by aromatase, more so with higher body fat. A baseline measured by LC/MS-MS (the standard immunoassay overreads at male levels) is useful when breast tenderness, fluid retention or mood symptoms appear later; guidelines do not recommend routine estradiol blocking, and the baseline is what keeps that decision data-driven.

TSH and vitamin D. Hypothyroidism mimics low testosterone symptoms and lowers SHBG; vitamin D deficiency is common in the same men. Neither is a TRT test strictly, but both are cheap to settle at the same draw.

• Fertility intent. TRT suppresses sperm production, sometimes for a year or more after stopping. Men who may want children should discuss alternatives (clomiphene, hCG) or sperm banking before starting; a semen analysis is the relevant baseline.
• Sleep apnea, uncontrolled heart failure, a recent heart attack or stroke, untreated prostate or breast cancer, a hematocrit over 50%, severe urinary symptoms — reasons guidelines say to treat first or not treat.
• Cardiovascular picture. The TRAVERSE trial (2023) found testosterone non-inferior to placebo for major cardiac events in hypogonadal men at elevated risk, with more atrial fibrillation, pulmonary embolism and acute kidney injury in the testosterone group — a reason the baseline includes blood pressure, lipids and glucose, and a reason the decision is a shared one.

After starting, the standard rhythm is testosterone, hematocrit and symptom review at 3 months (6–12 weeks), then PSA and hematocrit at 6 and 12 months and annually, with testosterone timed to the formulation (mid-interval for injections, 2–8 hours after a gel). The Quarterly Panel is built for exactly that visit; the Starting Panel is for the one before it.

Fast 8–12 hours, sleep normally the night before, skip hard training that morning, and arrive at the lab between 7 and 10 am. If you are on biotin supplements, stop them two days before — biotin interferes with several hormone immunoassays. Do not draw during a cold or within a few weeks of a significant illness or surgery, and tell your clinician about opioids, anabolic steroids, finasteride and glucocorticoids, all of which move these numbers. Repeat the testosterone on a second morning under the same conditions before accepting a low result.

Order online, walk into any Quest or Labcorp with your requisition, and results post to your account within one to three business days — bring the whole set to the prescribing clinician; the pattern across LH, SHBG, hematocrit and PSA is what makes the prescription safe, not the testosterone number alone.