Metabolic disorders induced by synthetic gestagens have been discussed under the aspect of single endocrine parameters or the carbohydrate or lipid metabolism. In order to obtain more complex information a prospective study of 26 patients was performed, who were treated with 1,000 mg medroxyprogesterone acetate (MPA) per day over a period of 5 weeks as a second-line therapy of breast cancer. Before treatment and afterwards once a week the serum concentrations of MPA, androstenedione, DHEA-S, cortisol, prolactin, insulin, c-peptide, glucose, cholesterol, triglycerides, phospholipids and the lipoprotein fractions (VLDL, IDL, LDL, HDL) were analyzed. Besides the reduction of the androgens and changes in the glucose regulation significant effects on the lipoprotein metabolism were observed, leading to the conclusion that under high-dose gestagen therapy very complex interactions of the endocrine and metabolic system occur.