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Internal Medicine

Hypercholesterolemia

Hypercholesterolemia also called high cholesterol, is the presence of high levels of cholesterol in the blood.

Hypercholesterolemia also called high cholesterol, is the presence of high levels of cholesterol in the blood.

Definition:

LDL-cholesterol > 190 mg/dL, or > 160 mg/dL + 1 major risk factor, or > 130 mg/dL with 2 CVS risk factors:
  • Age (♂ ≥ 45 years; ♀ ≥ 55 years)
  • Family history of premature atherosclerotic cardiovascular disease
  • Hypertension
  • Diabetes
  • Smoking
  • Low HDL-cholesterol levels (♂ < 40 mg/dl; ♀ < 55 mg/dl)

Physiology

Lipoprotein metabolism ABCA1 – ATP-binding cassette transporter A1, HDL – high density lipoprotein, LDL – low density lipoprotein, TG – triglycerides, SRB1 – scavenger receptor class B type 1, VLDL – very low density lipoprotein | Soran, H., Adam, S., Mohammad, J. B., Ho, J. H., Schofield, J. D., Kwok, S., Siahmansur, T., Liu, Y., Syed, A. A., Dhage, S. S., Stefanutti, C., Donn, R., Malik, R. A., Banach, M., & Durrington, P. N. (2018). Hypercholesterolaemia – practical information for non-specialists. Archives of medical science : AMS, 14(1), 1–21. https://doi.org/10.5114/aoms.2018.72238

Aetiology

Genetic causes:

  • Familial hypercholesterolemia (FH) (d/t defects in the LDL receptor (M/C), apolipoprotein B (ApoB), or proprotein convertase subtilisin/Kexin type 9 (PCSK9)
  • Autosomal recessive hypercholesterolemia (d/t mutation in LDL receptor adaptor protein resulting in defective endocytosis of the LDL receptors)

Secondary causes:

  • Hypothyroidism
  • Nephrotic syndrome
  • Cholestasis
  • Pregnancy
  • Drugs: Cyclosporine, thiazide, and diuretics

Clinical features

Although hypercholesterolemia itself is asymptomatic, longstanding elevation of serum cholesterol can lead to adverse cadiovascular complications.

Familial hypercholesterolemia (Type IIa hyperlipoproteinemia):

Features specific physical findings:
  • Xanthelasma palpebrarum (yellowish patches underneath the skin around the eyelids)
  • Arcus senilis (white or gray discoloration of the peripheral cornea)
  • Xanthomata (deposition of yellowish cholesterol-rich material) of the tendons, especially of the fingers

Complications:

Hypercholesterolaemia is one of the major modifiable risk factors for atherosclerotic cardiovascular disease (CVD), a global health problem
  • Heart Disease
  • Stroke
  • Peripheral vascular disease

Diagnosis

Plasma lipid profile:

Screening test recommended for all adults > 40 years, preferably after a 10-12-hour overnight fast
  • Friedewald formula: LDL-C = Total Cholesterol – VLDL(TG/5) – HDL-C

Exclusion of secondary causes:

  • TSH (hypothyroidism)
  • Glucose (diabetes)
  • Urinalysis
  • Serum albumin (nephrotic syndrome)
  • Bilirubin & alkaline phosphatase (cholestasis)

Management

Healthy lifestyle:

Cornerstone of treatment of hypercholesterolemia
  • Optimum weight
  • No smoking
  • Exercising for 150min/week
  • Dietary changes: Low saturated and trans-fatty acids and enriched in fiber, fruit, and vegetables and fatty fish

Medical management:

The decision to go beyond dietary advice and introduce lipid-lowering medication is based on an assessment of risk so that treatment is deployed in those who will benefit the most
  • Statins (first-line drugs)
  • Cholesterol absorption inhibitors (ezetimibe) and/or bile acid sequestrants (next-line drugs)

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