Thyroid function and autoimmune manifestations in insulin-dependent diabetes mellitus during and after pregnancy

Insulin-dependent diabetes is associated with other autoimmune diseases and subclinical hypothyroidism has been reported in pregnant diabetic women. We studied the thyroid function of 85 women with diabetes during pregnancy and after delivery, as well as various autoantibodies. During pregnancy, thyroid microsomal antibodies were present in 17/85, antibodies against thyroid peroxidase in 16/85, thyroglobulin antibodies in 2/85, parietal cell antibodies in 23/85, adrenal antibodies in 4/77, rheumatoid factor in 15/85, and thyroid-stimulating antibodies in 43/85. Presence of antibodies was not combined with thyroid dysfunction, but TSH and HbA1c was increased (p less than 0.005) in women with thyroid antibodies. The gestational age of the infants was lower (p less than 0.01) in women with positive thyroid-stimulating antibody titre, whereas the ponderal index was only lower in those with peroxidase antibodies (p less than 0.05). After delivery, microsomal and peroxidase antibodies were positive in 10 (17.5%) of 57 patients followed. Six women developed postpartum thyroiditis (10.5%), of whom 5 were positive for both microsomal and peroxidase antibodies; two of those showing a hyperthyroid phase also had positive thyroid-stimulating antibody titre. We conclude that autoantibodies occur with increased incidence in pregnant diabetic women. Thyroid antibodies are related to a slightly reduced thyroid capacity and involve a high risk of postpartum thyroiditis. Further, thyroid antibodies seem to influence the nutritional status of the infant.