Effects of dextro-thyroxine, a preparation almost free of levo-thyroxine, on thyroid function, serum lipids and apolipoprotein A-I in “Double pre-beta lipoproteinemia”

Eight subjects, belonging to a large family kindred repeatedly showing the electrophoretic pattern of the “double pre-beta lipoproteinemia”, were studied. In seven of them thyroid function, serum lipids and apolipoprotein A-I were determined before and after treatment with dextro-thyroxine, preparation almost free of levo-thyroxine. In most of the patients, total-T 4 levels and free-T 4 Index were in the lower normal range, but basal TSH levels and the TSH response to TRH weere normal. Dextro-thyroxine was effective in reducing both serum total cholesterol and triglycerides, but the percentage decrease in serum triglycerides was definitely greater than that of serum total cholesterol. This marked, unexpected hypotriglyceridemic effect is similar to that observed in a group of obese, hypertriglyceridemic hypothyroid patients treated with levo-thyroxine. Besides serum total cholesterol and triglycerides, the VLDL cholesterol/triglycerides ratio and the electrophoretic “slow moving” pre-beta component were also significantly reduced after treatment, suggesting that dextro-thyroxine can remove efficiently “remnant” VLDL particles from the plasma. Following dextro-thyroxine therapy, the relatively low pretreatment values of apolipoprotein A-I were significantly increased, being restored to normal.