Fatty Acids, Free
Free fatty acids are formed by the breakdown of lipoprotein and triglycerides. All but 2 " пїЅ5% of the serum fatty acids are esterified. The "nonesterified " пїЅ or "free " пїЅ fatty acids are protein bound. Epinephrine, norepinephrine, glucagon, TSH, and ACTH release free fatty acids. Tumors producing such hormones cause release of excessive quantities of free fatty acids. Other names: nonesterified fatty acids (NEFA), FFA.
Normal range:
Adults: 8 " пїЅ25 mg/dL or 0.28 " пїЅ0.89 mmol/L
Children (or obese adults): <31 mg/dL or <1.0 mmol/L
Use
Monitoring nutritional status in the presence of malabsorption, starvation, and long-term parenteral nutrition.
Valuable for the differential diagnosis of polyneuropathy when Refsum disease is suspected. In this disease, the enzyme that degrades phytanic acid is lacking.
Detection of pheochromocytoma and glucagon thyrotropin and adrenocorticotropin-secreting tumors.
Diabetes management.
Interpretation
Increased In
Poorly controlled DM
Pheochromocytoma
Hyperthyroidism
Huntington chorea
von Gierke disease
Alcoholism
Acute myocardial infarction
Reye syndrome
Phytanic acid increased in:
Refsum disease
Zellweger syndrome
Neonatal adrenoleukodystrophy
пїЅ пїЅ-Lipoproteinemia
Decreased In
CF
Malabsorption (acrodermatitis enteropathica)
Zinc deficiency (arachidonic acid and linoleic acid low)
Limitations
Free fatty acids increase by 12 " пїЅ25% in 24 hours in refrigerated plasma.
Strenuous exercise, anxiety, hypothermia, and long-term fasting elevate the levels.
Long-term IV or parenteral nutrition therapy decrease the levels.
Prolonged fasting or starvation affects levels (rise as much as three times normal).