Bioavailable Testosterone

Description

What is the SHBG (Male) Test?

The SHBG (Male) Test from BiomarkersLabs.com measures Sex Hormone-Binding Globulin in men — the principal transport protein for testosterone and oestradiol in the blood. SHBG is produced by the liver and binds testosterone with high affinity, rendering the bound fraction biologically inactive while in the bound state. Because SHBG directly determines the proportion of total testosterone that is free and biologically available, it is an essential contextual marker for interpreting total testosterone results in men.

SHBG levels in men are influenced by age (rising progressively with age), body composition (suppressed by obesity and insulin resistance), thyroid status (elevated in hyperthyroidism), liver function (reduced in liver disease), and certain medications. The clinical consequence of SHBG variation is substantial: two men with identical total testosterone values can have profoundly different free testosterone bioavailability depending on their SHBG level. An older lean man with elevated SHBG may have clinically deficient free testosterone despite a total testosterone in the normal range; an obese insulin-resistant man with suppressed SHBG may have adequate free testosterone despite a total testosterone that appears borderline low. SHBG measurement is therefore indispensable for accurate male hormonal assessment, hypogonadism diagnosis, and TRT monitoring. Results are CLIA-certified (USA) and IVDR-compliant (EU/UK), delivered to the practitioner portal within 1–3 business days.

What does the SHBG (Male) Test measure?

SHBG (Sex Hormone-Binding Globulin — male) — the primary testosterone transport protein. Elevated SHBG reduces free testosterone bioavailability and is associated with older age, hyperthyroidism, liver disease, and certain anticonvulsants. Suppressed SHBG increases free testosterone bioavailability and is associated with obesity, insulin resistance, hypothyroidism, and anabolic steroid use. SHBG measurement enables Calculated Free Testosterone (Vermeulen formula) and Free Androgen Index calculation from total testosterone alone, providing free androgen bioavailability estimates without requiring a separate free testosterone assay in many clinical settings.

Clinical indications

Hypogonadism investigation — total testosterone context — SHBG is essential whenever total testosterone is in the borderline range and symptoms of hypogonadism are present. Elevated SHBG confirms that free testosterone bioavailability is lower than total testosterone alone suggests; suppressed SHBG confirms that free testosterone may be adequate despite a low-appearing total testosterone.

Calculated free testosterone — enabling Vermeulen calculation — SHBG measured alongside total testosterone enables calculation of free testosterone using the Vermeulen formula, providing free androgen bioavailability assessment without requiring a separate free testosterone assay.

TRT monitoring — binding protein context — SHBG changes during TRT (particularly with different delivery routes — injectable testosterone markedly suppresses SHBG while transdermal has a lesser effect). Monitoring SHBG during TRT ensures free testosterone bioavailability is correctly interpreted alongside total testosterone results.

Metabolic syndrome and insulin resistance assessment — suppressed SHBG is an independent marker of insulin resistance and is included in male metabolic syndrome hormonal profiling. Low SHBG alongside testosterone and fasting insulin characterises the hormonal-metabolic interaction in obese and insulin-resistant men.

Age-related hormonal assessment in older men — the progressive rise in SHBG with age is a major driver of the age-related decline in free testosterone. SHBG measurement quantifies the binding protein contribution to andropause and guides decisions about testosterone optimisation.

Thyroid disease hormonal context — hyperthyroidism raises SHBG and reduces free testosterone bioavailability in men. SHBG measurement in men with thyroid disease provides the binding protein context for interpreting concurrent testosterone levels.

Sample type and collection

Blood (serum). No fasting required. Venepuncture at an approved collection site. SHBG can be drawn at any time of day — it does not follow significant diurnal variation. Most informative when measured concurrently with total testosterone in the same blood draw to enable free testosterone calculation.

Turnaround time

1–3 business days from specimen receipt.

Availability

USA · EU · UK · Canada

Compliance

CLIA Certified · IVDR Compliant · CE Marked · HIPAA Compliant · GDPR Compliant · PIPEDA Compliant

How to order

Register free at BiomarkersLabs.com. Licensed practitioners only. Pay per test — no subscription required. Results are delivered directly and securely to your practitioner portal and are never released directly to patients.