Metabolic studies in gestational diabetic women during contraceptive treatment: effects on glucose tolerance and fatty acid composition of serum lipids.

Abstract

Intravenous glucose tolerance tests (IVGTT) with simultaneous assessment of plasma insulin and analyses of the fatty acid composition of serum lecithin and cholesterol esters were performed in 11 women with previous gestational diabetes before and repeatedly during 6 months' administration of a low-dose progesterone (lynestrenol = LYN). 8 of these women were also followed in an identical manner during 6 months of nonhormonal contraception (intrauterine device = IUD) and additionally 6 of these women were followed also during the use of a combined oral contraceptive (OC) (ethinyl estradiol + lynestrenol - EE + LYN). LYN did not alter the IVGTT or plasma insulin but decreased the proportion of polyunsaturated fatty acids (PUFA) in serum lecithin (p less than 0.01) and cholesterol esters (p less than 0.01) where oleic acid was reciprocally increased (p less than 0.05). After 6 months' use of IUD, on the other hand, the k value of IVGTT increased by 45% (p less than 0.01) without significant changes in plasma insulin. In both lecithin and cholesterol ester PUFA increased (p less than 0.05) and cholesterol ester oleate decreased (p less than 0.01); i.e., virtually the reversal of the changes seen during LYN administration. The combined OC, EE + LYN, caused a decrease in the k value by 27% (p less than 0.05) which was apparent even when compared to the effects of LYN alone. EE + LYN also increased (p less than 0.05) lecithin palmitate and decreased stearate (p less than 0.05) and had a concomitant tendency to lower PUFA and increase oleic acid in both lecithin and cholesterol esters. These results indicate that LYN has little influence on the glucose tolerance in women predisposed to diabetes but may provide poorer conditions for dietary treatment of subclinical diabetes than do nonhormonal IUDs. The combined CO, EE + LYN, on the other hand, promptly diminishes glucose tolerance and may also have an unfavorable influence on liver metabolism.