Thyroxine replacement therapy enhances clearance of chylomicron remnants in patients with hypothyroidism

To further confirm the benefit of replacement therapy in terms of risk for coronary artery disease, we evaluated the effect of T-4 on postprandial lip oproteins in patients with hypothyroidism. Nine normolipidemic patients (ag ed 62.75 +/- 7.6 yr) with TSH of 32.2 +/- 13.2 mU/L and free T-4 of 0.66 +/ - 0.17 ng/mL were treated with T-4 (50-100 mu g/day) for at least 4 months. The behavior of postprandial lipoproteins was assessed before and during t reatment by determining retinyl palmitate levels in the total plasma, chylo microns (S-f > 1000) and chylomicron remnants (S-f < 1000) fractions for 8 h after a mixed meal plus vitamin A. During T-4 treatment, serum levels of TSH and FT, were 4.4 +/- 4.9 mU/L and 1.2 +/- 0.34 ng/mL (P = 0.001 and P = 0.002), respectively. Fasting low density lipoprotein cholesterol decrease d from 166 +/- 35 to 135 +/- 23 mg/dL (P = 0.035). Retinyl palmitate (RF) l evels in the chylomicron remnant fraction was reduced significantly during therapy from 6948 +/- 2790 to 5174 +/- 2401 mu g/L.h (area under the curve +/- SD; P = 0.014). Total plasma RP and chylomicron RP remained unchanged. We conclude that T-4 enhances the clearance of chylomicron remnants in norm olipidemic patients with hypothyroidism.