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510 Chapter 13: Nutritional and metabolic disorders

HDL Cell membrane
cholesterol

Cholesterol (endogenous & absorbed)
Triglycerides
Intestine
Apoproteins

LDL
Chylomicron

ILDL

VLDL
Removal of triglyceride
in the tissues

Figure 13.1 Cholesterol and triglyceride transport.

Most of these are broken down in the liver. Some are Hypercholesterolaemia: Heterozygous familial hyper-

further depleted of triglyceride and are released as cholestrolaemia (LDL receptor deficiency), homozy-
low-density lipoproteins (LDL) – the main cholesterol gous familial hypercholesterolaemia, defects in apo-
carrier. protein B.
High-density lipoproteins (HDL) from the intestine Combined hyperlipidaemia: Familial combined hy-

and the liver collect cholesterol from cell membranes perlipidaemia, remnant hyperlipidaemia.
in the tissue and transport it back to the liver.
Hyperlipidaemias are classified as primary and sec-
Clinical features
ondary (see Table 13.1).
The clinical signs of hypercholesterolaemia are pre-
Primary hyperlipidaemia is a group of inherited condi-
mature corneal arcus, xanthelasmata and tendon xan-
tions subdivided into those that cause hypertriglyceri-
thomata. Acute pancreatitis and eruptive xanthomata
daemia, hypercholesterolaemia and combined hyperlip-
are features of hypertriglyceridaemia. More commonly
idaemia.
it is diagnosed through targeted screening of high-risk
Hypertriglyceridaemia: Familial hypertriglyceri-

patients (family history of hyperlipidaemia or coro-
daemia, lipoprotein lipase deficiency, apoprotein C-II
nary heart disease, hypertensive, diabetic and obese
deficiency.
patients.
Table 13.1 Causes of secondary hyperlipdaemia
Complications
Hormonal Pregnancy, diabetes mellitus,
hypothyroidism Atherosclerosis leads to coronary heart disease, cere-
Liver disease Primary biliary cirrhosis, extrahepatic brovascular disease and peripheral vascular disease. Hy-
biliary obstruction pertriglyceridaemia can cause acute pancreatitis.
Nutritional Obesity, anorexia nervosa, alcohol abuse
disorders
Drug induced High dose thiazides, corticosteroids, sex Investigations
hormones
Renal dysfunction Nephrotic syndrome, chronic renal failure Random, non-fasting plasma cholesterol is used as a
screen in low-risk populations. Full fasting lipid profile,