In Vivo Insulin Action in Type 1 (Insulin-Dependent) Diabetic Pregnant Women as Assessed by the Insulin Clamp Technique*

Abstract

To determine the influence of pregnancy on insulin sensitivity in patients with type 1 diabetes mellitus in more detail, a hyperinsulinemic euglycemic clamp study was performed in six pregnant type 1 diabetic women and eight nonpregnant women with type 1 diabetes mellitus. All of the pregnant women were studied three times: in early pregnancy (mean, week 13), late pregnancy (mean, week 34), and within a week after delivery. Insulin was infused in a constant rate of 1.0 mU/kg-min, which resulted in steady state serum free insulin levels (I) of 44 ± 3 (±SEM), 56.6 ± 6, and 55 ± 8 μU/ml in the pregnant diabetic women and 52 ± 4 μU/l in the nonpregnant women. Mean glucose disposal (M) was 5.6 ± 0.3 mg/kgmin early in pregnancy and 3.4 ± 0.5 mg/kgmin late in pregnancy (P < 0.02). However, in the early postpartum period, M was again higher (7.2 ± 0.7 mg/kgmin; P < 0.02) and similar to values in early pregnancy and nonpregnant diabetic women (7.2 ± 0.6 mg/kg-min). When tissue sensitivity to insulin was expressed as the M to I ratio, similar results were obtained (nonpregnant women, early stage of gestation, and postpartum vs. late stage of gestation: 0.13 ± 0.01, 0.13 ± 0.01, and 0.15 ± 0.03 mg/kg-min per μU/ml vs. 0.06 ±0.1 mg/kgmin per μU/ml; P < 0.03 in all). There tended to be an inverse relationship between serum levels of human placental lactogen and the M to I ratio during pregnancy (r = –0.74; P = 0.09). However, we found no association between changes in the impairment of insulin action and serum estradiol, progesterone, or cortisol levels. In conclusion, pregnant type 1 diabetic women have insulin resistance in peripheral tissues in the late stage of gestation. Insulin sensitivity returns to values found in nonpregnant diabetic women within the first week after delivery. (J Clin EndocrinolMetab61: 877, 1985)