Primary hypophysitis is a rare inflammatory condition which is mostly encountered in women. It represents 0.20.8% of pituitary pathologies and its annual incidence is estimated at 1 case per 9 million inhabitants. We present the case of a 28-year-old male, smoker, with sudden onset decreased libido, polyuria and polydipsia. At presentation he had an epicranial lipoma with and no other suggestive clinical signs. Biochemistry revealed hypernatremia 146 nmol/L, low testosterone level 0.5 ng/mL, low normal FSH and LH, normal prolactin level, normal adrenal and thyroid function. The dehydration test was positive for central diabetes insipidus (test stopped after 4 hours due to high plasma osmolality- 307 mOsm/l while urinary osmolality was lower than 300 mOsm/l and increased to 756 mOsm/l after Desmopressin). Diagnosis of central diabetes insipidus and hypogonadotropic hypogonadism has been made. Pituitary MRI showed thickening of the pituitary stalk close to the chiasm, a homogenous enlarged pituitary gland with loss of posterior bright spot. Serum alpha-fetoprotein and β-HCG were negative both in blood and CSF and scrotal ultrasound was normal excluding germinoma; normal blood angiotensin-converting enzyme, negative tuberculin purified protein derivative test and normal chest CT excluded sarcoidosis, tuberculosis and lung cancer. Also CSFflow cytometry, serum IGG4, c-ANCA, HIV serology were normal. The patient was treated with Desmopressin and Testosterone undecanoate and reevaluated at 3 and 6 months - pituitary IRM showed regression of the pituitary stalk mass, with persistence of DI and hypogonadism. The etiological spectrum of pituitary stalk (PS) lesions is broad, presenting a diagnostic challenge. We will discuss the differential diagnosis and management of this unusual case of primary infundibulohypophysitis. Pituitary stalk biopsy in this case was considered deleterious and not absolutely necessary as repeated MRI at 3 months showed a reduction of the stalk lesion. In cases of suspected lymphocytic hypophysitis, it is reasonable to try a course of high-dose glucocorticoids before proceeding to PS biopsy. However a positive response to glucocorticoids is not specific for hypophysitis, as a temporary relief can be observed also in lymphoma and germinomas. Similarly, in the absence of mass effect symptoms, like in our case it is reasonable to observe a PS lesion ensuring close hormonal and radiological follow-up as spontaneous resolution of PS has been observed.
Conclusion: Primary hypophysitis occurring in a young man is a rare condition with poorly understood pathogenesis and lack of specific markers, thus represents a diagnostic challenge.
18 - 21 May 2019
European Society of Endocrinology