Unit Converter
Sex hormone‑binding globulin (SHBG)
Synonym
Human sex hormone-binding globulin, sex steroid-binding globulin (SSBG), Testosterone-estrogen Binding Globulin (TeBG)
Units of measurement
nmol/L, µg/mL, µg/dL, µg/100mL, µg%, µg/L, mg/L
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SEX HORMONE–BINDING GLOBULIN (SHBG)
(Major Carrier Protein for Testosterone & Estradiol — Essential for Calculating Free Hormones & Evaluating Androgen Disorders)
Synonyms
- SHBG
- Sex hormone–binding globulin
- Testosterone–binding globulin
- Androgen-binding protein (distinct but related)
- TeBG / SSBG (older)
Units of Measurement
- nmol/L
- µg/mL
- µg/dL
- µg/100 mL
- µg%
- µg/L
- mg/L
Unit Conversions
Molecular weight of SHBG ≈ 100,000–120,000 Da
(Common reference MW = 118 kDa)
Using 118 kDa:
nmol/L ↔ mg/L
1 nmol/L=118 mg/L1\ \text{nmol/L} = 118\ \text{mg/L}1 nmol/L=118 mg/L 1 mg/L=0.00847 nmol/L1\ \text{mg/L} = 0.00847\ \text{nmol/L}1 mg/L=0.00847 nmol/L
µg/mL ↔ mg/L
1 µg/mL=1 mg/L1\ \text{µg/mL} = 1\ \text{mg/L}1 µg/mL=1 mg/L
µg/dL → µg/L
1 µg/dL=10 µg/L1\ \text{µg/dL} = 10\ \text{µg/L}1 µg/dL=10 µg/L
µg% = µg/dL
Description
SHBG is a glycoprotein produced mainly by the liver that binds:
- Testosterone (highest affinity)
- Dihydrotestosterone (DHT)
- Estradiol (E2)
SHBG controls the bioavailability of sex steroids.
Only free + albumin-bound testosterone is considered bioavailable.
Thus, SHBG is crucial for:
- Evaluating male hypogonadism
- Assessing androgen excess in women
- Interpreting total testosterone correctly
- Calculating free testosterone (FT) via Vermeulen equations
Physiological Role
- Regulates free sex-hormone levels
- Ensures stable circulating testosterone
- Influences adiposity, insulin sensitivity, and metabolic risk
- Acts as a biomarker of liver function and metabolic health
Clinical Significance
HIGH SHBG
Causes
- Hyperthyroidism
- Pregnancy (estrogen effect)
- Oral contraceptives
- Liver disease (cirrhosis)
- HIV infection
- Aging
- Estrogen therapy
- Anorexia / malnutrition
Effects
- Low free testosterone
- Symptoms of hypogonadism despite normal total testosterone
LOW SHBG
Highly clinically relevant
Causes
- Obesity
- Insulin resistance
- Metabolic syndrome
- Type 2 diabetes
- Hypothyroidism
- PCOS (women)
- Androgen excess
- Nephrotic syndrome
- High-dose steroids
- Acromegaly
Effects
- Higher free testosterone
- In women → hirsutism, acne, PCOS-like symptoms
- In men → preserved FT despite low total T
Reference Intervals
(Tietz 8E + Endocrine Society + Mayo + ARUP)
Ranges vary by age & sex.
Adult Men
- 10 – 57 nmol/L
Adult Women
- 18 – 144 nmol/L
Postmenopausal Women
- 20 – 120 nmol/L
Children
- Levels are generally low until puberty.
Clinical Flags
- SHBG < 15 nmol/L → strongly suggests insulin resistance or androgen excess
- SHBG > 100 nmol/L → suspect hyperthyroidism, estrogen effect, pregnancy
Units Description
nmol/L
Preferred molar concentration.
mg/L / µg/mL / µg/L
Mass units derived from SHBG molecular weight.
µg/dL / µg%
Historical units.
Diagnostic Uses
1. Evaluation of Hypogonadism (Men)
Calculate free or bioavailable testosterone using SHBG:
- Total T may be “normal” but FT low due to high SHBG.
2. PCOS Evaluation (Women)
Low SHBG → high free androgen index (FAI).
3. Estrogen Status
Elevated SHBG reflects estrogen effect:
- Pregnancy
- OCP use
- HRT
4. Thyroid Disorders
SHBG ↑ with hyperthyroidism, ↓ with hypothyroidism.
5. Liver Disease
Cirrhosis → ↑ SHBG.
6. Metabolic Disorders
Low SHBG is a biomarker of:
- Metabolic syndrome
- NAFLD
- Insulin resistance
7. Aging
SHBG increases with age, lowering free T.
Analytical Notes
- Fasting not required
- Measured using immunoassays (chemiluminescence)
- Variability exists between platforms
- FT calculation should use same SHBG assay values
- Abnormal SHBG changes FT more than total T levels
Clinical Pearls
- Free testosterone should NEVER be interpreted without SHBG.
- Obesity → low SHBG → misleadingly normal free T despite low total T.
- Estrogen therapy ↑ SHBG → decreases free T → drives breast tenderness, libido changes.
- In PCOS, low SHBG is one of the earliest metabolic abnormalities.
- SHBG is a strong predictor of type 2 diabetes risk in both men and women.
Interesting Fact
Although SHBG is best known as a sex-hormone transporter, it also has receptors on cell membranes, suggesting additional signaling roles beyond hormone transport.
SEO Unit Converter Text
SHBG converter — convert between nmol/L, mg/L, µg/mL, µg/dL, µg%, and µg/L. Includes endocrine interpretation, metabolic syndrome associations, and free testosterone calculation insights.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition — Hormone Binding Proteins
- Endocrine Society Clinical Guidelines — Male Hypogonadism & PCOS
- Mayo Clinic Laboratories — SHBG
- ARUP Consult — SHBG & Testosterone Interpretation
- NIH / MedlinePlus — SHBG Test
- AACE – Endocrinology Guidelines
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