Transcriptional Regulation of Rat Hepatic Low-Density Lipoprotein Receptor and Cholesterol 7α Hydroxylase by Thyroid Hormone

Utilizing hypophysectomized and thyroidectomized rats, it is demonstrated that the rapid increase in expression of hepatic low-density lipoprotein (LDL) receptor and cholesterol 7α-hydroxylase in response to thyroid hormone is due to increases in the rates of transcription of these genes. An increase in transcription of the hepatic LDL receptor gene was seen within 30 min after administration of triiodothyronine. The increase in transcription fully accounted for the increase in hepatic LDL receptor protein. Stimulation of transcription of these two genes provides for enhanced removal of LDL from serum and elimination from the body.