Hyperlipidaemia: Primary vs Secondary, and When to Treat
Key points
- Hyperlipidaemia: raised total cholesterol, LDL cholesterol or triglycerides, or a low HDL cholesterol. Usually asymptomatic and detected on screening or after a cardiovascular event.
- Secondary causes must be excluded first: hypothyroidism, nephrotic syndrome, cholestasis, diabetes, alcohol excess, obesity and drugs such as thiazides, corticosteroids and antiretrovirals can all raise lipids and should be identified and treated before assuming primary disease.
- Familial hypercholesterolaemia (FH): autosomal dominant, usually an LDL receptor mutation, causing very high LDL from birth and premature cardiovascular disease. Diagnosed clinically with the Simon Broome or Dutch Lipid Clinic Network criteria.
- Signs of severe or familial disease: tendon xanthomata (classically Achilles), corneal arcus before age 45, xanthelasma, and eruptive xanthomata with severe hypertriglyceridaemia.
- Risk assessment: QRISK3 estimates 10-year cardiovascular risk for primary prevention in the general population, but is not used in FH, where statin treatment is indicated regardless of the calculated score because the genetic risk is already established.
- First-line drug treatment: a statin (HMG-CoA reductase inhibitor). NICE offers atorvastatin 20 mg for primary prevention where QRISK3 is 10% or above, and atorvastatin 80 mg for secondary prevention.
- Monitoring: LFTs before and during treatment, creatine kinase if myalgia occurs, and a repeat lipid profile at 3 months aiming for a greater than 40% reduction in non-HDL cholesterol.
- Add-on and alternative agents: ezetimibe for statin intolerance or insufficient response; PCSK9 inhibitors for FH or statin-intolerant high-risk patients; fibrates for severe hypertriglyceridaemia to reduce the risk of pancreatitis.
- Cascade testing: once FH is diagnosed, first-degree relatives should be offered genetic and lipid testing, since roughly half will carry the mutation.
Introduction
Hyperlipidaemia describes an abnormal lipid profile - most often a raised LDL cholesterol or raised triglycerides, sometimes with a low HDL cholesterol. It is extremely common, almost always asymptomatic, and matters because it is one of the strongest modifiable drivers of atherosclerotic cardiovascular disease and, at very high triglyceride levels, of acute pancreatitis.
The essential first step in any patient with an abnormal lipid profile is to work out why: is this a primary (genetic or idiopathic) lipid disorder, or is it secondary to another condition or drug? This distinction changes both the urgency of treatment and who else in the family needs testing.
Classification
Secondary hyperlipidaemia
Secondary causes are common and should always be sought and treated before a lipid abnormality is attributed to primary disease.1
| Cause | Typical lipid pattern |
|---|---|
| Hypothyroidism | Raised total and LDL cholesterol |
| Nephrotic syndrome | Markedly raised total and LDL cholesterol, from increased hepatic lipoprotein synthesis |
| Cholestasis / obstructive liver disease | Raised total cholesterol |
| Diabetes mellitus (poorly controlled) | Raised triglycerides, low HDL |
| Chronic kidney disease | Raised triglycerides |
| Alcohol excess | Raised triglycerides, risk of pancreatitis at extreme levels |
| Obesity / metabolic syndrome | Raised triglycerides, low HDL |
| Drugs - thiazide diuretics, corticosteroids, non-selective beta-blockers, antiretrovirals (protease inhibitors), ciclosporin, retinoids, antipsychotics | Variable - commonly raised triglycerides and LDL |
| Pregnancy | Physiological rise in triglycerides and cholesterol, normally transient |
Basic screening for a secondary cause therefore includes TFTs, fasting glucose or HbA1c, LFTs, U&Es, and urinalysis for proteinuria, alongside a careful drug and alcohol history.
Primary hyperlipidaemia
Once secondary causes have been excluded (or treated), a persistently abnormal lipid profile is considered primary. This ranges from common polygenic hypercholesterolaemia, driven by a combination of modest genetic susceptibility and lifestyle factors, through to specific inherited disorders.
| Disorder | Inheritance / mechanism | Key features |
|---|---|---|
| Familial hypercholesterolaemia (FH) | Autosomal dominant - usually a mutation in the LDL receptor gene, less often apolipoprotein B or PCSK9 | Very high LDL cholesterol from birth, premature coronary artery disease, tendon xanthomata, corneal arcus before 45 |
| Familial combined hyperlipidaemia | Polygenic, often with a family history of mixed dyslipidaemia | Raised LDL and triglycerides; variable phenotype even within the same family |
| Familial hypertriglyceridaemia | Polygenic or, rarely, monogenic (e.g. lipoprotein lipase deficiency) | Markedly raised triglycerides, risk of eruptive xanthomata and acute pancreatitis |
| Polygenic hypercholesterolaemia | Multiple common gene variants plus diet and lifestyle | Moderately raised LDL cholesterol; the commonest primary pattern seen in practice |
Familial hypercholesterolaemia
FH affects around 1 in 250 people in its heterozygous form, making it one of the commonest inherited conditions in medicine, yet it remains substantially under-diagnosed.2 The homozygous form is rare (around 1 in 300,000) but causes extremely high LDL cholesterol and coronary disease in childhood.
Untreated heterozygous FH carries a markedly increased risk of premature coronary artery disease - historically around 50% of men and 30% of women developed coronary disease by age 50 and 60 respectively without treatment. Early recognition and statin treatment substantially reduce this risk.
Diagnostic criteria
FH is a clinical diagnosis, supported by genetic testing where available. Two scoring systems are used in the UK and Europe:
- Simon Broome criteria - combine a raised total or LDL cholesterol with either tendon xanthomata (in the patient or a first/second-degree relative) or DNA-confirmed FH-causing mutation, or a family history of premature coronary disease or very high cholesterol, to classify as 'definite' or 'possible' FH
- Dutch Lipid Clinic Network (DLCN) criteria - a points-based score incorporating family history, clinical history of premature cardiovascular disease, physical examination (tendon xanthomata, corneal arcus before 45), LDL cholesterol level, and DNA analysis, stratifying into 'definite', 'probable', 'possible' or 'unlikely' FH
NICE recommends suspecting FH in adults with a total cholesterol above 7.5 mmol/L, or a personal or family history of premature coronary heart disease (onset before 60 in a first-degree relative, or before 50 in men more generally used as a threshold prompt).2
Cascade testing
Once an index case is diagnosed, cascade testing - systematically offering lipid and, where available, genetic testing to first-degree relatives, then extending outward through the family - identifies affected relatives early, often in childhood, when treatment can prevent decades of cumulative LDL exposure. Each affected relative has, on average, a 50% chance of passing the mutation to their own children.2
Clinical features
Hyperlipidaemia itself is usually asymptomatic and found incidentally on screening, during cardiovascular risk assessment, or after a myocardial infarction or stroke. The physical signs below are seen mainly in severe or familial disease and should always prompt a search for FH or severe hypertriglyceridaemia.
| Sign | Description | Association |
|---|---|---|
| Xanthelasma | Yellowish cholesterol deposits in the skin around the eyelids | Can occur with normal lipids, but more often reflects raised LDL cholesterol; more specific for dyslipidaemia when seen before middle age |
| Corneal arcus | A grey-white ring at the corneal margin | Common and non-specific over 60. Before age 45 it is a sign suggestive of FH. |
| Tendon xanthomata | Firm, painless nodules within tendons, classically the Achilles tendon and extensor tendons of the hands | Highly specific for familial hypercholesterolaemia |
| Eruptive xanthomata | Crops of small yellow papules with an erythematous base, typically over the buttocks and extensor surfaces | Reflect severe hypertriglyceridaemia and mark a substantial risk of acute pancreatitis |
| Lipaemia retinalis | Creamy white retinal vessels seen on fundoscopy | Very severe hypertriglyceridaemia |
Investigations
Full lipid profile - total cholesterol, LDL cholesterol, HDL cholesterol and triglycerides. A non-fasting sample is now generally acceptable for routine screening and risk assessment; a fasting sample is preferred where triglycerides are very high or when monitoring a known lipid disorder, since triglycerides rise after eating.3
- Non-HDL cholesterol (total cholesterol minus HDL cholesterol) is the value NICE uses to set and monitor treatment targets, since it captures all atherogenic (apolipoprotein B-containing) particles and does not require fasting
- Secondary cause screen - TFTs, fasting glucose/HbA1c, LFTs, U&Es and urinalysis, as above
- QRISK3 - calculates 10-year cardiovascular risk for primary prevention in the general population aged 25-84 without pre-existing cardiovascular disease. Not used in FH or in established cardiovascular disease, where treatment is offered regardless of the score
- Consider FH-specific assessment (Simon Broome or DLCN criteria, and referral for genetic testing) if total cholesterol is very high, there are tendon xanthomata, or there is a family history of premature cardiovascular disease
Management
Lifestyle measures
Offered to everyone, and address the modifiable drivers of secondary and polygenic dyslipidaemia directly: a diet lower in saturated fat and higher in fibre, weight loss where appropriate, regular physical activity, smoking cessation, and reduced alcohol intake. Lifestyle measures alone rarely normalise LDL cholesterol in FH, where drug treatment is required regardless.
Statins
Statins (HMG-CoA reductase inhibitors) are first-line drug treatment. They competitively inhibit HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis; the liver responds by upregulating LDL receptor expression, increasing clearance of LDL from the circulation.4
| Indication | NICE recommendation |
|---|---|
| Primary prevention | Atorvastatin 20 mg where QRISK3 is 10% or above, after discussing lifestyle measures. Offer to anyone who requests it after an informed discussion of risks and benefits, even below this threshold. |
| Type 1 diabetes | Consider atorvastatin 20 mg if aged over 40, diabetes duration over 10 years, established nephropathy, or other cardiovascular risk factors are present |
| Type 2 diabetes / chronic kidney disease | Atorvastatin 20 mg, following the same QRISK3-based approach, though most will exceed the 10% threshold |
| Secondary prevention (established atherosclerotic cardiovascular disease) | Atorvastatin 80 mg, regardless of QRISK3 - risk assessment tools are not used once disease is established |
| Familial hypercholesterolaemia | High-intensity statin (e.g. atorvastatin 80 mg), started regardless of QRISK3, aiming for at least a 50% reduction in LDL cholesterol |
Monitoring
- LFTs before starting, and typically at 3 and 12 months - stop or reduce the dose if transaminases rise to more than 3 times the upper limit of normal
- Lipid profile at 3 months, aiming for a greater than 40% reduction in non-HDL cholesterol from baseline; increase adherence support or the dose if this is not achieved
- Creatine kinase if the patient develops myalgia - measure before starting only in those at higher risk of myopathy (e.g. history of muscle disorders)
- Statins are usually taken at night because hepatic cholesterol synthesis is greatest overnight, although atorvastatin and rosuvastatin have a long enough half-life that timing matters less
Add-on and alternative agents
| Drug | Mechanism | Main use |
|---|---|---|
| Ezetimibe | Inhibits intestinal cholesterol absorption (NPC1L1 transporter) | Added to a statin if the non-HDL target is not met, or used alone if statins are not tolerated |
| PCSK9 inhibitors (e.g. alirocumab, evolocumab) | Monoclonal antibodies that inhibit PCSK9, increasing LDL receptor recycling and hepatic LDL clearance | Familial hypercholesterolaemia, or statin-intolerant patients with high cardiovascular risk and LDL remaining above NICE thresholds despite ezetimibe. Given by subcutaneous injection. |
| Fibrates (e.g. fenofibrate) | PPAR-alpha agonists, mainly lowering triglycerides and raising HDL | Severe hypertriglyceridaemia, particularly to reduce the risk of acute pancreatitis |
| Omega-3 fatty acid supplements | Reduce hepatic triglyceride synthesis | Adjunct in severe hypertriglyceridaemia; evidence for cardiovascular benefit is weak |
| Bile acid sequestrants (e.g. colestyramine) | Bind bile acids in the gut, increasing hepatic LDL receptor expression | Now rarely used - poorly tolerated (bloating, constipation) and superseded by ezetimibe |
Complications
- Atherosclerotic cardiovascular disease - coronary artery disease, ischaemic stroke and peripheral arterial disease, the dominant long-term consequence of raised LDL cholesterol
- Acute pancreatitis - from severe hypertriglyceridaemia
- Premature coronary disease in FH, sometimes presenting as myocardial infarction in the third or fourth decade if undiagnosed and untreated
Red flags
Prognosis
For most patients, treated hyperlipidaemia carries a good prognosis: statins produce a dose-dependent reduction in LDL cholesterol and a proportional reduction in cardiovascular events, with benefit accruing over years. In familial hypercholesterolaemia, early diagnosis and treatment substantially reduce the historically very high rate of premature coronary disease, which is why cascade testing of relatives is so important. Severe hypertriglyceridaemia carries an ongoing risk of pancreatitis until triglycerides are controlled, and repeated episodes can lead to chronic pancreatitis and diabetes.
References
- NICE Clinical Knowledge Summaries. Lipid modification - CVD prevention. Available here
- NICE CG71. Familial hypercholesterolaemia: identification and management. 2008, updated 2019. Available here
- NICE NG238. Cardiovascular disease: risk assessment and reduction, including lipid modification. 2023. Available here
- BNF. Statins - indications, dosing and interactions. Available here
- Klaus D. Peter, Wiehl, Germany, CC BY 3.0 DE, via Wikimedia Commons. Available here
This article is written for revision and education. It is not clinical guidance and must not be used to make decisions about the care of a patient. Always check current NICE guidance and local protocols.