Effect of thyroid function on pre-β1 high-density lipoprotein levels in patients with Graves’ disease undergoing radioiodine treatment

Context The metabolism of HDL is altered in thyroid dysfunctions. Preβ-1 HDL is a very small discoidal precursor HDL and promotes cholesterol efflux via ABCA 1 . The effects of thyroid dysfunctions on pre-β1 HDL are unknown. Thyroid hormone regulates ANGPTL3 expression, which may participate in HDL metabolism in thyroid dysfunctions. Objective To determine the variation of HDL subfractions, especially preβ-1 HDL in thyroid dysfunctions, and whether ANGPTL3 mediates the effect of thyroid function on HDL metabolism. Methods We recruited 26 patients with Graves’ disease undergoing radioiodine treatment. They were evaluated at three time points: at baseline, when they were hypothyroid after radioiodine treatment, and when they were on stable levothyroxine replacement and euthyroid. Results The concentrations of smaller HDL particles Preβ-1 HDL and HDL3 were highest at the hyperthyroid state, and lowest at the hypothyroid state. While the larger HDL particles HDL2 and HDL1 changed just the opposite. Preβ1-HDL and HDL3 were positively correlated to fT 3 and fT 4 , while were negatively correlated to TSH. In contrast, HDL1 was negatively associated with fT 3 and fT 4 , while was positively associated with TSH. The correlations between thyroid hormones and HDL subfractions remained significant after adjusting for ANGPTL3. Conclusions There is a shift form smaller HDL particles pre-β1 HDL and HDL3 to larger HDL particles HDL2 and HDL1 in hypothyroidism, while the change is just the opposite in hyperthyroidism. In future, cholesterol efflux capacity should be measured to determine if the function of HDL particles also changes with the shifting of HDL subfractions.