The short answer is no they do not. The long answer is more complicated because some studies that have reported blood cholesterol altering effects from increasing dietary consumption of eggs may not have controlled for confounding variables adequately. In particular changes to the energy, fibre or polyunsaturated fat intakes can all confound the data if they are not carefully controlled. Well controlled studies have generally shown that eggs do not cause changes to blood cholesterol levels in healthy humans. For example, one study added one egg per day1 and another study 2 eggs per day2, to a normal but low cholesterol diet for 3 months and found no significant response to serum cholesterol levels. In another study, two eggs per day were added to the diets of hospitalised patients for 54 days but no changes to serum cholesterol levels occured3. A fourth study added two eggs per day to the normal egg containing diet of healthy men and then removed all eggs from the diet, but this did not alter blood cholesterol levels4.
1Porter, M. W., Yamanaka, W., Carlson, S. D. and Flynn, M. A. 1977. Effect of dietary egg on serum cholesterol and triglyceride of human males. American Journal of Clinical Nutrition. 30(4): 490-495
2Flynn, M. A., Nolph, G. B., Flynn, T. C., Kahrs, R. and Krause, G. 1979. Effect of dietary egg on human serum cholesterol and triglycerides. American Journal of Clinical Nutrition. 32(5): 1051-1057
3Kummerow, F. A., Kim, Y., Hull, J., Pollard, J., Ilinov, D. L. 1977. The influence of egg consumption on the serum cholesterol level in human subjects. American Journal of Clinical Nutrition. 30(5): 664-673
4Slater, G., Mead, J., Dhopeshwarkar, G. and Alfin-Slater. 1976. Effect of eating eggs on plasma cholesterol levels in young and middle aged men. Nutrition Report International. 14: 249