Beyond MRI: Unveiling metabolic signatures of primary hypophysitis with 18F-FDG PET

Abstract Aims Hypophysitis is a heterogeneous clinical entity originating from different anatomical compartments of the pituitary gland and driven by diverse pathophysiological mechanisms. This study aims to explore the potential diagnostic and clinical value of 18 F-fluorodeoxyglucose positron emission tomography in the evaluation of primary hypophysitis. Materials and methods This single-center retrospective study was conducted at the pituitary referral unit of a tertiary university hospital. The study population included patients with primary hypophysitis, individuals with nonfunctioning pituitary adenomas, and subjects without intracranial pathology. Demographic features, baseline clinical and biochemical characteristics, as well as initial cranial and sellar magnetic resonance imaging and 18 F-fluorodeoxyglucose positron emission tomography findings, were systematically analyzed and compared across groups. Furthermore, in the primary hypophysitis subgroup, potential associations between positron emission tomography imaging parameters and clinical, radiological, and laboratory characteristics were specifically examined. Results A total of 46 participants were enrolled in the study, comprising 16 patients with primary hypophysitis, nine with nonfunctioning pituitary adenoma, and 21 controls without intracranial pathology. Positron emission tomography demonstrated significantly higher maximum and mean standardized uptake values in patients with primary hypophysitis compared with controls, whereas no significant differences were observed between the other groups. Within the primary hypophysitis cohort, mean standardized uptake values were significantly elevated in patients with hypopituitarism and in those with Arginine vasopressin deficiency (central diabetes insipidus) compared to their respective counterparts without these conditions. Furthermore, both maximum and mean standardized uptake values were markedly higher in patients with growth hormone deficiency than in those with preserved growth hormone function. Conclusion These findings suggest that metabolic activity observed on 18 F-fluorodeoxyglucose positron emission tomography may serve as a marker of disease severity and pituitary dysfunction in primary hypophysitis.