After an overnight fast, serum will be assayed from subjects between 8 and 9 am to control for diurnal variation. Blood samples will be collected and processed by nurses at the Grady GCRC core laboratory. Serum will be sent to the lab of Dr. George Beck and stored at -80◦C. The following analyses will be done at the end of the study in a single batch for each marker. Please see table 2 for details of each assay.