Triglycerides - Kresser Institute Membership Site

Marker Name: Triglycerides

REFERENCE RANGES FOR TRIGLYCERIDES:

Laboratory reference range: 0–149 mg/dL

Functional reference range: 50–100 mg/dL

DESCRIPTION:

A triglyceride is the combination of a glycerol molecule and three fatty acids connected through ester linkages.¹ Triglycerides are one of the major lipids found in the serum and are a major component of fat cells (adipocytes). Triglycerides are the primary energy storage molecule; they can enter the bloodstream from dietary sources or can be released from adipocytes to act as a rapid energy source.^2,3 The ability to store triglycerides and release this energy when food is scarce is important for survival.²

Triglycerides can be synthesized within intestinal cells from the enzymatic combination of free fatty acids and glycerol.⁴ Triglycerides join cholesterol to form chylomicrons, which can travel to various tissues throughout the body. Chylomicrons can release free fatty acids as an immediate energy source or transfer fatty acids to adipocytes for storage.⁴ Very low-density lipoproteins (VLDL) may also shuttle triglycerides released from the liver to peripheral tissues or for storage in adipocytes.⁵

Blood triglyceride levels may increase as much as five- to tenfold after a meal, which is why most clinicians order triglycerides in fasting patients. Non-fasting triglycerides may be more representative of typical circulating triglyceride levels; however, it is unclear how to interpret non-fasting triglyceride levels at this point.³ If tissues demand a source of energy between meals, triglycerides can be liberated through lipolysis. Lipolysis, or the hydrolysis of triglycerides, occurs predominantly in adipocytes.⁵ Lipolysis is under tight hormonal regulation and is affected by insulin and circulating catecholamines, particularly epinephrine and norepinephrine.⁵

An abnormally high level of circulating triglycerides is called hypertriglyceridemia. It may be due to a primary genetic disorder such as familial hypertriglyceridemia or, more often, a secondary cause.⁶ Secondary causes of hypertriglyceridemia include obesity, insufficient physical activity, and excessive alcohol consumption.⁷ Certain endocrine diseases such as diabetes mellitus and hypothyroidism can cause an elevation in triglycerides. Kidney disease, particularly uremia and glomerulonephritis, can elevate triglyceride levels. High triglyceride levels are noted in otherwise healthy women in the third trimester of pregnancy, which is considered a normal biological response to pregnancy.⁸ Several drugs can increase triglycerides in the blood, including corticosteroids, oral estrogens, certain blood pressure medications, and certain antipsychotics.⁵

An abnormally low triglyceride level is called hypotriglyceridemia. Hypotriglyceridemia is associated with certain genetic conditions such as hereditary abetalipoproteinemia, hypobetalipoproteinemia, and Williams-Beuren syndrome.^9,10 Certain chronic infections such as hepatitis B, hepatitis C, and HIV/AIDS can cause prolonged hypertriglyceridemia. Various autoimmune conditions are associated with low triglyceride levels, and hypotriglyceridemia may herald the onset of some autoimmune conditions.¹¹ Exercise and severe malnutrition will also lower circulating triglycerides.^12,13

Triglycerides are reported as part of a serum lipid profile or lipid panel. The serum lipid profile includes total cholesterol, HDL cholesterol, and LDL cholesterol. This report may also provide calculated estimates of VLDL cholesterol, non-HDL cholesterol, and the cholesterol/HDL ratio.¹⁴

PATHOLOGICAL/CONVENTIONAL RANGE INDICATIONS: High in:^6-8

Primary hypertriglyceridemia
- Chylomicronemia
- Familial hypertriglyceridemia
- Familial combined hyperlipidemia
- Familial dysbetalipoproteinemia
- Hypertriglyceridemia and serum cholesterol
Normal pregnancy (third trimester)
Obesity
Insufficient physical activity
Alcohol consumption
Diabetes mellitus
Hypothyroidism
Renal disease (e.g., uremia, glomerulonephritis)
Autoimmune conditions (e.g., systemic lupus erythematosus)
Drugs
- Corticosteroids
- Oral estrogens
- Tamoxifen
- Beta-blockers
- Thiazides
- Isotretinoin
- Bile acid binding resins
- Cyclophosphamide
- Antiretrovirals
- Phenothiazines
- Atypical antipsychotics

Low in:^9-13,15

Heritable conditions
- Hereditary abetalipoproteinemia
- Hypobetalipoproteinemia
- Williams-Beuren syndrome
Autoimmune conditions
Hyperthyroidism
Malnutrition and undernutrition
Alcohol consumption
HIV/AIDS
Hepatitis (chronic, active hepatitis B, hepatitis C)
Drugs
- Fibrates
- Statins
- Nicotinic acid

FUNCTIONAL RANGE INDICATIONS:

High in:

Non-fasted state (make sure patient was fasting)
Early insulin resistance
Hypothyroidism

Low in:

Malabsorption
Hyperthyroidism
Autoimmune disease (some clinicians have empirically noted low triglyceride levels in patients with autoimmune disease)

References: