Summary
Eight patients with primary hypothyroidism were compared to eleven euthyroid subjects
with regard to the effects of a single i.v. dose of heparin on plasma lipoprotein
concentrations (the “clearing reaction”).
The hypothyroid patients were moderately hypercholesterolemic but had normal plasma
triglyceride levels. Maximal activities of hepatic lipase (HL) and lipoprotein lipase
(LPL) were lower in the hypothyroid than in the normal subjects. The hypothyroid patients
demonstrated a significant decrease in total plasma cholesterol levels after heparin
injection (from 8.36 ± 0.70 mmol/l to 7.55 ± 0.62 mmol/l, P < 0.02). The maximal activity
of HL after heparin was significantly correlated to the decrease in plasma cholesterol
levels (P < 0.05) and in LDL-cholesterol levels (P < 0.01). The euthyroid subjects
demonstrated a smaller decrease in total plasma cholesterol concentrations (from 5.53
± 0.31 to 5.08 ± 0.28 mmol/l, P < 0.05). In this group, the fall in cholesterol levels
was not correlated to maximal HL activity. The reduction in plasma triglyceride levels
after heparin was similar and significant (P < 0.01) in both groups.
These data support the view that decreased activity of HL contributes to the dyslipoproteinemia
seen in hypothyroidism. They are also in accordance with the notion that HL is involved
in the elimination of cholesterol from plasma.
Key-Words
Hypothyroidism
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Heparin
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Hypercholesterolemia
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Hepatic Lipase
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Lipoprotein Lipase
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Lipoproteins
