PROSPECTIVE EVALUATION OF INSULIN-RESISTANCE AND LIPID-METABOLISM IN WOMEN RECEIVING ORAL-CONTRACEPTIVES

OBJECTIVES It has been suggested that normal women receiving oral cont raceptives (OC) may develop a series of metabolic side-effects which r elate to the risk of cardiovascular disease. These metabolic disturban ces include changes in glucose and insulin metabolism, raised serum li pid and lipoprotein concentrations and elevated blood pressure. All th ese changes indicate that OC might cause insulin resistance. We have p rospectively examined the effect of OC on insulin resistance and lipid metabolism including Lp(a) values. PATIENTS The study group comprised 13 normally menstruating Chinese women. DESIGN The study subjects wer e given a combined triphasic oral contraceptive which was administered on a 21-day on, 7-day off medication cyclic regimen, the first pill b eing administered on day 5 from the beginning of menses. The metabolic investigations were carried out during luteal phase before OC and aga in the third week of the third month of OC administration. MEASUREMENT S Metabolic evaluation including insulin secretion and insulin-mediate d glucose uptake were evaluated by oral glucose tolerance test and the modification of insulin suppression test. Pasting triglyceride, chole sterol, HDL-cholesterol and Lp(a) concentrations were also measured. R ESULTS The plasma glucose and insulin responses during a 75-g oral glu cose challenge increased significantly (P<005 and P<0.03, respectively ). The steady-state plasma glucose (SSPG) concentrations achieved duri ng constant infusion of glucose, insulin and somatostatin increased si gnificantly after 3 cycles of OC administration (glucose 7.5+/-0.8 vs 12.4+/-0.7 mmol/l, P<0.001) while the steady-state plasma insulin (SSP I) concentrations were relatively similar (410+/-14 vs 391+/-7 pmol/l, NS). Plasma triglyceride levels increased significantly (0.81+/-0.12 vs 1.09+/-0.19 mmol/l, P<0.03) following OC administration. Pasting pl asma cholesterol, HDL cholesterol and calculated LDL cholesterol conce ntrations did not change as compared with baseline values, nor did the ratio of total cholesterol to HDL cholesterol. The Lp(a) concentratio ns did not change during the administration of OC (81+/-25 vs 71+/-21 mg/l, NS). CONCLUSIONS These data indicated that intake of OC for 3 cy cles induced glucose intolerance, hyperinsulinaemia and insulin resist ance in normal menstruating Chinese women. These changes occurred in a ssociation with elevated plasma triglyceride concentrations and no alt eration in Lp(a) or other lipid values.