Objective: Postpartum thyroiditis (PPT) is an autoimmune thyroid disease which shares immunological and clinical features with autoimmune hypothyroidism and Graves' disease, and is believed to be caused by a combination of genetic and environmental factors. Recently, an association has been described between Graves' disease or autoimmune hypothyroidism and a polymorphism in the CTLA-4 gene, which encodes a T cell receptor for the B7 family of ligands, and we wished to test whether a similar association exists with PPT.
Design: A population-based case-control study of a CTLA-4 gene microsatellite polymorphism was performed, to look for an association with PPT.
Patients: Caucasoid women (n = 122) were studied; 58 had thyroid antibodies (against thyroglobulin or thyroid peroxidase) alone during the postpartum period (PPT-) and 64 had thyroid antibodies and some form of postpartum thyroid dysfunction (PPT+).
Results: There was no significant difference between this whole group of women and 161 local Caucasoid thyroid antibody-negative women for the CTLA-4106 base pair (AT)n microsatellite polymorphism (relative risk = 1.3; P = 0.3), nor did the PPT+ group differ from controls when analysed separately (P = 0.2). When the postpartum women were subdivided in groups according to clinical pattern of PPT and the type of thyroid antibodies, there were no associations within the subgroups.
Conclusions: No significant association exists between postpartum thyroiditis and a polymorphism in the CTLA-4 gene. Furthermore, a natural variation in the prevalence of the polymorphism in healthy UK populations underscores the need to select appropriately matched normal subjects in future case-control studies.