Effects of L-thyroxine on serum lipid profiles in infants with congenital hypothyroidism.

Serum lipid profiles and the effects of thyroid hormone on them were studied in infants with congenital hypothyroidism. Serum total cholesterol, high-density lipoprotein cholesterol (HDLC), and low-density lipoprotein cholesterol levels were increased in infants with hypothyroidism;L-thyroxine therapy decreased the HDLC levels, leading to a reduction in serum concentrations of total cholesterol. It appears that thyroid hormone suppresses circulating HDLC, although the mechanism was not discovered in this study.