Anterior pituitary autoantibodies in patients with type 1 diabetes mellitus: methodological problems and clinical correlations

Background: Anti-pituitary antibodies (APA) were described in patients with Type 1 Diabetes (T1D) but their prevalence and relevance remain controversial. Materials and methods: We evaluated the APA prevalence in Sardinian sera from 100 T1D patients, 70 Type 2 Diabetes (T2D) patients and 62 healthy controls, using indirect immunofluorescence on bovine pituitary sections. To compare two different substrates, we tested using bovine sections, further T1D patient sera (n = 11, from Pisa) previously analysed for APA on monkey sections, while some T1D Sardinian patient sera (n = 22) were tested on monkey sections. According to preliminary experiments, positivity were considered ≥1:200 and ≥1:20 for bovine and monkey substrates, respectively. Results and discussion: Using bovine sections, APA were detected in 7/100 Sardinian T1D patients (at 1:200 titer) and in none of the other Sardinian sera tested. When the T1D sera from Pisa were tested on bovine and the T1D Sardinian sera were tested on monkey, none of these sera showed corresponding positivity for APA. Pituitary hormone dysfunctions were not found in the 7 APA-positive Sardinian T1D patients. The present study shows that the presence of APA at low-titer is highly related to T1D but not associated with any pituitary dysfunction while the animal species used as substrate appears crucial. Conclusion: Further studies are needed to ascertain whether APA detected by different animal species may have different pathological relevance in T1D and/or whether APA in the long run may predict future anterior pituitary dysfunction.