Extreme insulin resistance during pregnancy: a therapeutic challenge.

Summary During pregnancy, maternal tissues become increasingly insensitive to insulin in order to liberate nutritional supply to the growing fetus, but occasionally insulin resistance in pregnancy becomes severe and the treatment challenging. We report a rare and clinically difficult case of extreme insulin resistance with daily insulin requirements of 1420 IU/day during pregnancy in an obese 36-year-old woman with type 2 diabetes (T2D) and polycystic ovary syndrome (PCOS). The woman was referred to the outpatient clinic at gestational week 12 + 2 with a hemoglobin A1c (HbA1c) at 59 mmol/mol. Insulin treatment was initiated immediately using Novomix 30, and the doses were progressively increased, peaking at 1420 units/day at week 34 + 4. At week 35 + 0, there was an abrupt fall in insulin requirements, but with no signs of placental insufficiency. At week 36 + 1 a, healthy baby with no hypoglycemia was delivered by cesarean section. Blood samples were taken late in pregnancy to search for causes of extreme insulin resistance and showed high levels of C-peptide, proinsulin, insulin-like growth factor (IGF-1), mannan-binding-lectin (MBL) and leptin. CRP was mildly elevated, but otherwise, levels of inflammatory markers were normal. Insulin antibodies were undetectable, and no mutations in the insulin receptor (INSR) gene were found. The explanation for the severe insulin resistance, in this case, can be ascribed to PCOS, obesity, profound weight gain, hyperleptinemia and inactivity. This is the first case of extreme insulin resistance during pregnancy, with insulin requirements close to 1500 IU/day with a successful outcome, illustrating the importance of a close interdisciplinary collaboration between patient, obstetricians and endocrinologists. Learning points This is the first case of extreme insulin resistance during pregnancy, with insulin requirements of up to 1420 IU/day with a successful outcome without significant fetal macrosomia and hypoglycemia. Obesity, PCOS, T2D and high levels of leptin and IGF-1 are predictors of severe insulin resistance in pregnancy. A close collaboration between patient, obstetricians and endocrinologists is crucial for tailoring the best possible treatment for pregnant women with diabetes, beneficial for both the mother and her child.