Key Biomarkers Explained: What Each Marker Tells You About Your Health

Most at-home biomarker panels measure the same core set of markers — but unless you know what each number means, results can feel like noise. This guide explains the markers most commonly tested in hormone and metabolic health panels, what optimal and concerning ranges look like, and what follow-up action abnormal values typically warrant.

Testosterone Markers

Total Testosterone

The most commonly tested hormone marker. Measures the total amount of testosterone in your blood — both bound and unbound.

• Typical range (men): 300–1,000 ng/dL
• Low (<300 ng/dL): May indicate hypogonadism — associated with fatigue, low libido, mood changes, and muscle loss. Clinical diagnosis requires two separate morning draws.
• High (>1,000 ng/dL): Can indicate exogenous testosterone use, certain tumors, or congenital conditions.

Free Testosterone

The fraction of testosterone not bound to proteins — the biologically active portion that can enter cells and produce effects.

• Why it matters: Some men have normal total testosterone but low free testosterone due to elevated SHBG, which can cause the same symptoms as low total T.
• Low free T with normal total T: Suggests elevated SHBG — common in older men, those with liver disease, or those on certain medications.

SHBG (Sex Hormone-Binding Globulin)

A protein that binds to testosterone and estrogen, reducing their bioavailability.

• High SHBG: Reduces free testosterone — a common contributor to low-T symptoms even with normal total T levels.
• Low SHBG: Increases free testosterone — can be associated with insulin resistance and metabolic syndrome.

Estrogen Markers

Estradiol (E2)

The primary form of estrogen. Present in both men and women and measured as part of all hormone panels.

• In men: Normal range 10–40 pg/mL. Testosterone aromatizes (converts) to estradiol — elevated estradiol in men on TRT can cause water retention, mood changes, and gynecomastia. Low estradiol causes joint pain and reduced libido.
• In women: Varies significantly across the menstrual cycle and menopause transition. Key marker for HRT candidacy assessment.

Pituitary Hormones

LH (Luteinizing Hormone)

Released by the pituitary gland to signal the testes to produce testosterone.

• Low LH + low testosterone: Secondary hypogonadism — pituitary or hypothalamic cause
• High LH + low testosterone: Primary hypogonadism — testicular cause
• Important for TRT candidates: LH levels go to near zero on exogenous testosterone, so measuring baseline LH is important for anyone concerned about fertility.

FSH (Follicle-Stimulating Hormone)

Regulates sperm production in men and egg development in women.

• Low FSH + low testosterone: Points to pituitary dysfunction
• High FSH in women: Can indicate perimenopause or primary ovarian insufficiency

Thyroid Markers

TSH (Thyroid-Stimulating Hormone)

The primary screening marker for thyroid function. Released by the pituitary to stimulate thyroid hormone production.

• High TSH: Indicates hypothyroidism (underactive thyroid) — commonly associated with fatigue, weight gain, cold sensitivity, and brain fog
• Low TSH: Indicates hyperthyroidism (overactive thyroid) — associated with weight loss, anxiety, and rapid heartbeat
• Optimal range: Many functional medicine practitioners target 1.0–2.5 mIU/L rather than the broader conventional range of 0.4–4.0 mIU/L

Safety and Metabolic Markers

Hematocrit / Hemoglobin

Measures the percentage of red blood cells in blood.

• Why it matters for TRT: Testosterone stimulates red blood cell production. Elevated hematocrit (>52–54%) on TRT increases blood viscosity and clotting risk — a key safety marker requiring monitoring every 3–6 months on therapy.

PSA (Prostate-Specific Antigen)

A protein produced by prostate cells. Elevated PSA can indicate benign prostate enlargement, prostatitis, or prostate cancer.

• Baseline PSA: Required before starting TRT — active or suspected prostate cancer is a contraindication
• Monitoring: PSA should be checked annually on TRT; a significant rise warrants urological evaluation

Prolactin

A hormone that regulates reproductive function. Elevated prolactin in men suppresses testosterone production.

• Elevated prolactin: Can indicate a pituitary adenoma (benign tumor) — warrants MRI and endocrinology referral if significantly elevated

Frequently Asked Questions

Which markers are most important to test first?

For anyone concerned about hormone health or considering TRT or HRT, the core starting panel is: total testosterone, free testosterone, SHBG, estradiol, LH, FSH, TSH, CBC (with hematocrit), and PSA (for men). This covers diagnostic essentials and safety screening in one draw.

How often should I retest biomarkers?

For people on hormone therapy: every 6–12 weeks after starting or changing doses, then every 3–6 months on stable therapy. For general monitoring without active treatment: annually is typically sufficient for most markers.

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