Unit Converter
Fructose
(Key Monosaccharide – Used in Metabolic Disorders & Semen Analysis)
Synonyms
- Fructose
- Levulose
- Fruit sugar
- Seminal fructose (in semen analysis)
- Blood fructose
Units of Measurement
- mmol/L
- µmol/L
- mg/dL
- mg/100 mL
- mg%
- mg/L
- µg/mL
Key Conversions
(Molecular Weight = 180.16 g/mol)
1 mg/dL = 0.0555 mmol/L
1 mg/L = 0.00555 mmol/L
1 µg/mL = 1 mg/L
mg/dL = mg% = mg/100 mL
1 mmol/L = 1000 µmol/L
Description
Fructose is a naturally occurring monosaccharide found in:
- Fruits
- Honey
- Corn syrup
- Vegetables
In clinical biochemistry, fructose testing is important mainly in:
- Diagnosis of metabolic disorders (e.g., hereditary fructose intolerance)
- Assessment of male fertility through semen fructose levels
- Rare disorders of fructose metabolism
- Monitoring of fructose ingestion (diet studies)
Physiological Role
In Blood
Circulating fructose levels are typically very low.
The liver rapidly converts fructose into:
- Glucose
- Glycogen
- Lactate
In Semen
Fructose is produced by the seminal vesicles.
It is the primary energy source for sperm motility.
Clinical Significance
1. In Blood (Metabolic Disorders)
Elevated Fructose
Occurs in:
- High fructose intake
- Fructose malabsorption
- Essential fructosuria (benign, due to fructokinase deficiency)
Low Fructose
Seen in:
- Hereditary fructose intolerance (HFI) – aldolase B deficiency
- Severe liver disease
- Poor absorption
- Disorders of carbohydrate metabolism
HFI symptoms after fructose intake:
- Hypoglycemia
- Vomiting
- Sweating
- Seizures
- Jaundice
- Hepatomegaly
2. In Semen (Male Infertility Evaluation)
This is the most common clinical use of fructose measurement.
Low or Absent Seminal Fructose
Suggests:
- Absence or obstruction of seminal vesicles
- Ejaculatory duct obstruction
- Congenital absence of vas deferens (CFTR mutation)
- Seminal vesicle dysfunction
- Hypogonadism
Normal Seminal Fructose
Indicates:
- Functioning seminal vesicles
- Adequate androgen stimulation
- Normal accessory gland secretion
Reference Intervals
Blood Fructose
(Tietz 8E + Mayo)
- <0.2 mmol/L (≈ <3.6 mg/dL) - normal fasting
Levels rise only after fructose ingestion.
Seminal Fructose (WHO Andrology Manual)
Most clinically relevant reference:
- ≥ 13 µmol per ejaculate (or ≥13 µmol/sample)
- Reported alternatively as ≥2.4 mg/ejaculate
Absence = seminal vesicle dysfunction or obstruction.
Diagnostic Uses
1. Metabolic Disease Evaluation
- Hereditary fructose intolerance
- Essential fructosuria
- Fructose malabsorption
2. Male Infertility Testing (Primary Use)
- Obstruction of seminal vesicles
- Ejaculatory duct obstruction
- Congenital absence of vas deferens
- Post-vasectomy follow-up
- Assessing androgen-dependent gland function
3. Nutritional & Research Testing
Used in dietary research, absorption tests, metabolic studies.
Analytical Notes
- Blood fructose is measured by enzymatic or HPLC methods
- Seminal fructose measured via resorcinol or enzymatic assays
- Semen samples must be fresh (≤1 hour)
- Hemolysis does not significantly alter fructose
Clinical Pearls
- Absence of fructose in semen strongly suggests obstruction of seminal vesicles or ejaculatory ducts.
- Hereditary fructose intolerance presents with hypoglycemia after fructose intake.
- Essential fructosuria is benign and asymptomatic.
- High fructose diets may increase triglycerides and insulin resistance.
- Always correlate semen fructose with semen volume, sperm count, and pH.
Interesting Fact
Fructose was first isolated from fruit juices in the mid-19th century and is the sweetest naturally occurring sugar.
References
- Tietz Clinical Chemistry & Molecular Diagnostics, 8th Edition - Carbohydrates & Sugars.
- WHO Andrology Manual - Seminal Biochemistry.
- AACE/ACE Metabolic Guidelines.
- Mayo Clinic Laboratories - Fructose.
- ARUP Consult - Carbohydrate Metabolism Disorders.
- MedlinePlus / NIH - Fructose Tests.