Longitudinal combined evaluation of antipituitary antibody titer and immunofluorescence pattern is a suitable tool in predicting autoimmune hypophysitis in patients with autoimmune polyendocrine syndromes
Elena Pane1, Mario Rotondi2, Caterina Colella1, Assunta Dello Iacovo1, Liliana Dalla Mora3, Giuseppe Bellastella1, Antonio Agostino Sinisi1, Antonio Bizzarro1, Luca Chiovato2, Antonio Bellastella1 & Annamaria De Bellis1
Antipituitary antibodies (APA) are frequently present in patients with autoimmune polyendocrine syndrome (APS) but their role in predicting autoimmune hypophysitis (LYH) is still discussed.
To evaluate the predictive value of APA investigated by immunofluorescence for the occurrence of pituitary autoimmune dysfunction when considering together some methodological characteristics as immunostaining pattern and antibody titers, we studied 149 APA positive and 50 APA negative patients with APS but without pituitary dysfunction, following them up for a time-span of 5 years.
APA by indirect immunofluorescence and anterior pituitary function were assessed every 6 months in all patients.
Results: Among the 149 initially APA positive patients, 98 were positive at low/middle titer (65.7%) and 51 at high titer (34.3%). As regards the immunostaining pattern, 99 patients (66.4%) showed an immunostaining only involving few or several isolated pituitary cells (type 1 pattern) and 50 (33.6%) showed an immunostaining involving all pituitary cells (type 2 pattern). During the follow-up all 50 APA negative patients maintained a normal pituitary function. Instead, among the 149 APA positive patients, 28 (6 at low/middle and 22 at high titer at start) developed hypopituitarism, while 121 (92 at low/middle and 29 at high titer) did not. Interestingly, all patients developing pituitary dysfunction had shown a type 1 immunostaining at start and an increase of APA titer during the follow-up, while all patients showing at start type 2 immunostaining pattern maintained a normal pituitary function at the end with decrease of APA titer until disappearance in most of them. Statistical analysis of our data showed that either higher titer and type 1 pattern, considered separately, are unsuitable predictive markers of pituitary dysfunction, instead, a significant predictive value is obtained considering together these 2 parameters.
Conclusions: The predictive value of APA by immunofluorescence is still discussed due to some methodological problems. Our results indicate that APA could be considered good predictive markers of autoimmune pituitary dysfunction when considering together their titers and some particular characteristics of immunofluorescence pattern. The value of estimated risk of these findings may be useful to decide an appropriate follow-up of patients with APS without pituitary dysfunction and possible future immune-therapy strategies.