Since the plasma cholesterol level is elevated in myxedema, diabetes, nephrosis, and obstructive jaundice, falling levels observed in treatment of these conditions give additional proof that the disease is abating or responding to therapy. However, in obstructive jaundice, a fall in level of cholesterol without a fall in serum bilirubin level may be an ominous warning of parenchymal liver damage. In familial xanthomatosis also, falling levels of plasma cholesterol are evidences of response to diet, drugs, or heparin and may foretell resorption of yellow plaques in the skin.
The normal level of plasma cholesterol, in adults or children living on a diet of vegetables and fish, is between 120 and 160 mg. per 100 ml. Levels under 120 mg. per 100 ml. are usually due to diseases of the liver or the jejunum. However, very few people can approach this optimal level when the diet contains eggs, dairy products, and animal fat.