gestational diabetes mellitus ( gdm ) , which is close to type  2 diabetes mellitus , develops in 26% of pregnancies . in addition , a risk of developing autoimmune diseases , such as type  1 diabetes mellitus and autoimmune thyroid disease , increases in the postpartum period . classic type  1a diabetes is classified as autoimmune diabetes , characterized by autoantibodies such as glutamic acid dehydrogenase ( gad ) . postpartum graves disease is known to occur and account for 10% of postpartum autoimmune thyroid disease ( ppats ) . in the present case report , we report a case of a patient with gestational diabetes that is complicated with graves disease and type  1 diabetes mellitus after delivery . the present case was a 28yearold woman with a family history of type  2 diabetes . fasting plasma glucose level was 7.8  mmol / l ( 140  mg / dl ) in the 32nd week of pregnancy . she was then diagnosed with gdm and treated by diet modification . the baby ( 3780  g bodyweight ) was delivered by cesarean section in the 40th week of pregnancy . a month after delivery , her height was 163  cm , bodyweight was 54.0  kg and body mass index was 22.9 . physical examination showed that her thyroid gland was swelling at a degree of iii and a diffuse goiter was detected by ultrasound sonography . laboratory tests showed 9.9  mmol / l ( 178  mg / dl ) fasting plasma glucose level , and 8.0% hemoglobin a1c ( hba1c ) . thyroidstimulating hormone ( tsh ) level was 1.05  u / ml , thyroid microsomal antigen ( mcha ) was positive ( 1:1600 ) . it has been concluded that the patient had developed diabetes after delivery and had been treated by dietary modification . three months after delivery , the patient presented with palpitations and finger tremor . on laboratory examination , the free t4 level was 7.77  ng / dl and the free t3 level was 26.3  pg / ml . tsh level was lower than 0.05  u / ml and tsh receptor antibody ( trab ) was positive ( 30.4% ) . she was diagnosed with postpartum thyroid dysfunction ( graves disease ) and given propylthiouracil . after 6  months from delivery , the patient showed poor glycemic control , and high levels of urine and serum ketones . the patient s plasma glucose level was elevated to 24.6  mmol / l ( 443  mg / dl ) , hba1c level was 12.1% and serum cpeptide level was 0.47  ng / dl . antigad antibody was 144  u / ml and insulin autoantibody was 6.1% . based on these results , after 11  months from delivery , trab became negative and thyroid dysfunction showed remission . the patient gave her written informed consent for publication of the present case report in journal of diabetes investigation . the initiating factor is likely to be increased peripheral insulin resistance of normal pregnancy , but in an attempt to overcome the increased insulin resistance , relative pancreatic insufficiency develops . it is known that women with gdm have a considerable risk of developing type  2 diabetes later in life . this response is known to have a risk of causing autoimmune disease including type  1 diabetes and autoimmune thyroid disease to the mother . type  1 diabetes is thought to arise from an autoimmune attack against the pancreatic cells , which leads to failure to regulate blood glucose levels . usually , antibodies against islets , insulin and gad are found to be positive in patients . the presence of antimicrosomal antibodies , a family history of autoimmune disease and insulin dependent diabetes are known to increase its risk . highrisk mothers for postpartum thyroid dysfunction are well screened by mcha and antithyroid therapy might be a good choice for firstline therapy , as postpartum graves hyperthyroidism is often transient . there was also a report showing the development of both type  1 diabetes and graves disease after delivery . the association of gad with thyroid antibodies might be explained by the fact that gad is not exclusively present in the brain and pancreas , but can also be found in the thyroid gland . it has been reported that in patients with type  1 diabetes and graves disease , hladrb1 * 0405dqb1 * 0401 haplotype was detected and thelper  1 lymphocytes in peripheral blood were reduced . in addition , hyperthyroidism might aggravate glucose intolerance by multiple mechanisms . in the case of our patient , although the pathological mechanism of gdm is considered to be analogous to that of type  2 diabetes , gdm developed into type  1 diabetes with the presence of islet antibodies . in the past , it has been reported that gdm has a risk of developing into type  1 diabetes as well . jrvelet  al . reported that 4.6% of gdm developed into type  1 diabetes , whereas 5.3% developed into type  2 diabetes . they also identified that young age ( < 30  years ) , the need for insulin treatment during pregnancy , and positivity for islet cell antibodies ( ica ) and gad conferred a high risk of progression to type  1 diabetes . suggested that cell autoantibodies determined at delivery in gdm were highly predictive for the development of type  1 diabetes in the postpartum period . however , by screening with all three markers ( gad , ica and antibodies to the protein tyrosine phosphataserelated protein  2 molecule ; ia2a ) , sensitivity can be increased up to 82% . they also pointed out that women with one or more pregnancies before the index pregnancy had a higher risk for developing type  1 diabetes after delivery compared with women who were in their first pregnancy . usually , the examination of gad antibodies is used for the screening of type  1 diabetes in japan . the aforementioned findings emphasized the importance of screening and monitoring highrisk gdm patients , not just after delivery , but during pregnancy and at delivery . in addition , the importance of checking all available autoimmune antibodies in diagnosing type  1 diabetes in gdm patients . interestingly in our case , trab became negative and thyroid dysfunction showed remission , whereas still gad remained positive . postpartum graves disease is usually transient . although it is likely that in the case of our patient both graves disease and type  1 diabetes had a common cause , only graves disease was transient whereas type  1 diabetes remained permanent .