Serum levels of cholesterol and lipoproteins in rhesus monkeys: comparison of the effect of gonadotropin-releasing hormone agonist and the progestin, levonorgestrel

Levonorgestrel, a progestational steroid, and the more widely used antigonadotropin, danazol have been used in the treatment of endometriosis. Both of these agents decrease serum levels of HDL cholesterol. Recently, GnRH agonists came into use for treatment of endometriosis. Our objective in this study was to compare the effects of levonorgestrel and a GnRH analog on serum cholesterol levels in rhesus monkeys being treated for surgically induced endometriosis. A high dose of levonorgestrel significantly reduced total serum cholesterol and HDL cholesterol during a 12-week treatment period. Levonorgestrel had no significant effects on the concentration of LDL/VLDL cholesterol or the percentage of total cholesterol in the HDL fraction. Conversely, the GnRH agonist had no significant effect on total serum cholesterol, HDL cholesterol, LDL/VLDL cholesterol, or the percentage of HDL cholesterol. Because the concentration of HDL cholesterol is closely correlated with atherosclerotic risk, this factor should be weighed in the overall risk/benefit analysis for the patient with endometriosis.