Hyperlipidaemia
Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management
Definition
Hyperlipidaemia is a metabolic disorder characterised by elevated levels of lipids (cholesterol, triglycerides) in the blood, increasing the risk of cardiovascular disease.
Aetiology
- Primary hyperlipidaemia: genetic disorders affecting lipid metabolism (e.g., familial hypercholesterolaemia).
- Secondary hyperlipidaemia: caused by lifestyle factors (diet, obesity, sedentary lifestyle) or underlying conditions (e.g., diabetes mellitus, hypothyroidism, chronic kidney disease, nephrotic syndrome).
- Drug induced: corticosteroids, thiazide diuretics, beta-blockers, antipsychotics.
Pathophysiology
- Disruption of lipid metabolism leads to accumulation of low-density lipoprotein (LDL) and triglycerides in circulation.
- Elevated LDL cholesterol promotes atherosclerosis by depositing cholesterol in arterial walls, leading to plaque formation and increased cardiovascular risk.
- High density lipoprotein (HDL) has a protective effect by removing excess cholesterol from peripheral tissues.
Risk Factors
- Family history of hyperlipidaemia or premature cardiovascular disease.
- Obesity and metabolic syndrome.
- Poor diet high in saturated fats and refined carbohydrates.
- Physical inactivity.
- Smoking and excessive alcohol consumption.
- Underlying conditions (e.g., diabetes, hypothyroidism, renal disease).
Signs and Symptoms
- Asymptomatic: often detected incidentally through routine lipid screening.
- Cardiovascular complications: angina, myocardial infarction, stroke.
- Cutaneous signs: xanthomas (lipid deposits in tendons), xanthelasma (lipid deposits around the eyes).
- Corneal arcus: white or grey ring around the cornea in younger individuals.
- Pancreatitis: in cases of severe hypertriglyceridaemia (>10 mmol/L).
Investigations
- Lipid profile: measures total cholesterol, LDL, HDL, and triglycerides.
- Fasting or non fasting lipids: fasting preferred if hypertriglyceridaemia is suspected.
- Thyroid function tests: assess for hypothyroidism as a secondary cause.
- Liver function tests: to assess liver health before initiating lipid-lowering therapy.
- HbA1c and fasting glucose: screen for diabetes mellitus.
- Renal function tests: assess for chronic kidney disease.
Management
1. Lifestyle Modifications:
- Dietary changes: reduce saturated fats, trans fats, and refined sugars; increase fibre and omega-3 fatty acids.
- Weight loss: achieve and maintain a healthy BMI.
- Regular physical activity: at least 150 minutes of moderate intensity exercise per week.
- Smoking cessation: reduces cardiovascular risk.
- Limit alcohol intake: especially in hypertriglyceridaemia.
2. Pharmacological Therapy:
- Statins (e.g., atorvastatin, simvastatin): first line for LDL reduction and cardiovascular risk reduction.
- Ezetimibe: adjunct therapy if statins are insufficient or not tolerated.
- PCSK9 inhibitors (e.g., evolocumab, alirocumab): for high-risk patients with familial hypercholesterolaemia.
- Fibrates (e.g., fenofibrate): for severe hypertriglyceridaemia to prevent pancreatitis.
- Omega-3 fatty acids: useful in hypertriglyceridaemia.
3. Monitoring:
- Repeat lipid profile 6–12 weeks after initiating therapy, then annually.
- Monitor liver enzymes and muscle symptoms in patients on statins. Repeat LFT in 2-3 months.
4. Referral:
- Lipid clinic: for familial hypercholesterolaemia or refractory hyperlipidaemia.
- Endocrinology: if secondary causes such as hypothyroidism or metabolic syndrome require specialist input.
- Cardiology: if there is established cardiovascular disease or high cardiovascular risk.