Endocrine Abstracts

Background: The incidence of gestational diabetes appears to be rising, likely related to the increasing prevalence of overweight/obesity in the general population, and the trend of increasing maternal age. However, it must be remembered that some women newly diagnosed with diabetes in pregnancy have latent type 1 diabetes; GAD (glutamic acid decarboxylase) antibody measurement may be useful in cases with atypical features. We present two such cases.

Case 1: 31-year-old woman diagnosed with gestational diabetes (OGTT at 24/40: fasting glucose 4.6, 120 min 14.1 mmol/l; HbA1c 6%) during her second pregnancy, conceived on clomiphene for anovulatory PCOS. Her first pregnancy was complicated by pre-eclampsia: 3.5 kg infant delivered at 38 weeks. She had one grandparent with type 2 diabetes. Insulin treatment commenced at 26/40, and regimen titrated to effect. An unusual pattern of insulin requirements emerged: prandial novorapid doses 58/0/4 units pre-delivery. Normal foetal growth was observed; a healthy 2.9 kg infant delivered at 38/40. Postnatal testing showed impaired glucose tolerance. She re-presented 14 months later with osmotic symptoms, BMI 18, HbA1c 9.9%. Treatment with gliclazide/rosiglitazone initiated in primary care had been ineffective; she was seen in hospital and recommenced insulin, HbA1c falling to 6.6% after 6 months. GAD antibody positive, consistent with type 1 diabetes.

Case 2: A 28-year-old woman had diet-treated gestational diabetes in 2004 (OGTT: fasting glucose 4.2, 120 min 10.6 mmol/l), delivered a healthy 4.62 kg infant, and was normoglycaemic postpartum. There was a family history of type 1 diabetes. During her second pregnancy, 2 years later, gestational diabetes reoccurred, requiring insulin treatment (predelivery novorapid doses: 20/18/34 units). She delivered at term (3.62 kg infant); post-partum glucose 3.6 mmol/l. At 3 months postpartum, she presented with osmotic symptoms and marked weight loss; random glucose 22.5 mmol/l, HbA1c 10.5%, GAD antibody positive, C-peptide 566 pmol/l. Insulin was recommenced, with rapid resolution of symptoms; HbA1c 6.1% after 2 months.