Role of 18F-fluorodeoxyglucose (FDG) and 18F-2-fluorodeoxy sorbitol (FDS) in autoimmune hypophysitis: a case report

Abstract

Background: Autoimmune hypophysitis is a rare disease characterized by the infiltration of lymphocytic cells into the pituitary gland. ¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-2-fluorodeoxy sorbitol (FDS) positron emission tomography (PET) are well-established and emerging techniques, respectively, which may aid in the diagnosis and classification of autoimmune hypophysitis.

Case presentation: Here, we report a 40-year-old female diagnosed with central diabetes insipidus and multiple pituitary hormone deficiencies, and MRI revealed homogeneous signals in the pituitary gland as well as thickened in the pituitary stalk. FDG PET localized the pituitary and pituitary stalk lesions and displayed an SUVmax of 5.5. FDS, a sensitive radiotracer for bacterial infections but remains unproven under aseptic inflammation, also demonstrated elevated radioactivity, with an SUVmax of 1.1 at 30 min and 0.73 at 120 min. Transnasal biopsy suggested a diagnosis of autoimmune hypophysitis, and the patient displayed radiological and clinical improvement after treatment with glucocorticoids and hormone replacement.

Conclusions: Autoimmune hypophysitis can display elevated FDG uptake, which aids in the localization of the lesions. In addition to revealing bacterial infection specifically, FDS can also accumulate under autoimmune conditions, suggesting that it could serve as a potential radiotracer for both bacterial and aseptic inflammation.

Trial registration: The patient was enrolled in study NCT02450942 (clinicaltrials.gov, Registered May 21, 2015).

Keywords: Autoimmune hypophysitis; Case report; FDG; FDS; PET.

Fig. 1

Contrast-enhanced T1-weighted and T2-weighted MR images of the lesions. a-b. Pituitary with a size of 18.6 mm × 8.2 mm × 9.9 mm displayed a contrast-enhanced signal, and a lesion with a size of 6.5 mm × 5.2 mm × 4.6 mm and a relative hypointense contrast-enhanced signal was located (arrow noted). The pituitary stalk with a size of 5.1 mm × 1.7 mm showed an isointense contrast-enhanced signal (arrowhead noted) compared with the normal pituitary stalk. c. The pituitary lesion presented a hyperintense T2-weighted signal (arrow noted), and the thickened pituitary stalk exhibited an isointense T2-weighted signal in comparison with the normal pituitary. d-f. Contrast-enhanced T1-weighted and T2-weighted MR images of the lesions 3 years after surgery. The pituitary displayed postsurgical changes with no significant hypointense contrast-enhanced signal or hyperintense T2-weighted signal, and the pituitary stalk thickness was reduced (3.0 mm × 2.0 mm, arrowhead noted) compared with pretreatment MRI

Fig. 2

FDG and FDS activity of the lesions. a-d. Both the pituitary and pituitary stalk lesions displayed FDG activity with an SUVmax of 5.5 after 40 min of radiotracer injection. e-f. Both lesions displayed FDS activity with a SUVmax of 1.1 at 30 min after FDS injection; in comparison, the SUVmax of the normal brain tissue was 0.15, and the T/N ratio was 7.3. g-h. The lesions remained FDS active after 120 min of FDS administration with a SUVmax of 0.73; the SUVmax of the normal brain and the T/N ratio were 0.08 and 9.1, respectively

Fig. 3

FDG and FDS activity in a patient with a normal pituitary. a-d. Both the pituitary and pituitary stalks did not display FDG activity. e-h. FDS was also not absorbed in normal pituitary and pituitary stalks