Endocrine Abstracts

Introduction: Gestational diabetes mellitus (GDM) is a common and increasing complication, concerning 2–17% of pregnancies [1]. This glucose intolerance often resolves after delivery, and rarely becomes permanent type 2 diabetes, exceptionally type 1 diabetes (T1D). We present a case of a patient with GDM, which unexpectedly revealed T1D.

Case report: A 33-year-old woman consulted for GDM. Her family medical history includes hypothyroidism in her maternal aunt and psoriasis in her daughter. Our patient has had two COVID-19 infections. During her first pregnancy, she had gestational hypertension but no history of GDM or macrosomia. Prior to her pregnancy, the patient had a BMI of 30.8 kg/m²;. Her GDM was diagnosed at 26 weeks’ amenorrhoea through systematic screening. The patient had no previous carbohydrate assessment. Dietary management was sufficient to achieve glycemic targets for the rest of the pregnancy. Maximum weight was 82 kg. Five months after delivery, our patient lost 5 kilograms in 2 weeks. The glycemic cycle was between 0.86-2.02 g/l and HbA1C at 8.1%. The patient benefited from a basal insulin regime as she was breastfeeding. The evolution was marked by an increase in glycemia with the appearance of a polyurea-polydipsic syndrome despite insulin therapy, reaching a plateau of 2.5-3 g/l. Diabetes antibodies were requested (after 9 months postpartum), and were positive: Anti-GAD65 = 18.84 IU/ml, anti-IA2 = 88 IU/ml confirming T1D.

Discussion and conclusion: Our patient presented with a picture typical for T2DM. T1DM was unlikely given the good response to dietary management. The predictive factors for T1DM in patients with GDM are the presence of diabetes-related autoantibodies, which is the main factor, age < 30 years, the need for insulin treatment, and multiparity. The familiar history of autoimmunity should raise the possibility of T1D, even with such an atypical metabolic phenotype. Some studies have assessed phenotypic traits associated with autoimmunity among women with gestational diabetes: a lower BMI, a lower waist measurement, a lower weight gain during pregnancy, which was the case of our patient, and lower fasting insulin levels. Most studies identified an increased risk for many autoimmune diseases among patients with COVID-19. The explanation for our patient would be a partial and slowly progressive autoimmune destruction of pancreatic β cells, during pregnancy. In fact, many autoimmune diseases go into remission during pregnancy secondary to natural immune tolerance.