Endocrine Abstracts

Introduction: Arginine vasopressin deficiency (AVP-D) is a rare disorder with diverse etiologies. Approximately 30% of cases are labelled idiopathic, often associated with an underlying autoimmune process. This case report presents a previously presumed idiopathic AVP-D, revealing its aetiology after more than a decade of follow-up.

Case presentation: A 19-year-old male presented in 2012 with symptoms of AVP-D and non-pruritic papular skin lesions on the limbs. Hormonal evaluation confirmed complete AVP-D, and Desmopressin treatment was started. Pituitary MRI revealed the absence of physiologic hyperintense signal of the posterior pituitary on T1-weighted images and a moderate pituitary stalk thickening (PST), with an anteroposterior diameter of 3 mm at the level of the optic chiasm and 2 mm at the pituitary gland insertion, along with a transverse diameter of 5.1 mm, exhibiting a round shape. Thoracic radiography showed normal findings. The dermatological evaluation considered both guttate psoriasis and pityriasis rosea Gilbert as possible diagnostics, and treatment with erythromycin and corticosteroids was recommended, with remission of the skin lesions. After two years of follow-up, hypogonadotropic hypogonadism developed (FSH<0.2 mU/ml, LH=0.84 mU/ml, Testosterone=0.17 ng/ml), and testosterone substitution was given. Additionally, the IGF-1 levels were lower than the sex- and age-specific limits (IGF-1=89.2 ng/ml, RR 197-333). Serial pituitary MRIs indicated stable stalk thickness until 2022 when an increase was noted (transverse diameter 5.9 mm). In the same year, abdominal pain, cough and weight loss of 16 kg in 6 months led to the presumed diagnosis of sclerosing cholangitis (SCH) in the context of cystic fibrosis. SCH progressed to severe liver cirrhosis, necessitating transplantation. The patient received Tacrolimus 3 mg/day and oral Methylprednisolone 6 mg/day. Subsequently, considering the presumed diagnosis, a pulmonary consultation was performed, ruling out the diagnosis of cystic fibrosis. Nine months post-transplantation, endocrinological reassessment in the absence of testosterone substitution showed remission of hypogonadism (LH=4.82 mU/ml, FSH=2.63 mU/ml, Testosterone=3.75 ng/ml). The coexistence of SCH, pulmonary cysts and AVP-D raised the suspicion of Langerhans cell histiocytosis (LCH), confirmed by immunohistochemistry on the hepatic specimen. The patient was referred to a haematologist for appropriate treatment.

Conclusion: Regular, long-term follow-ups for AVP-D and PST patients, assessing ‘risk’ organs, remain essential. A definitive diagnosis for biopsy-worthy conditions may enhance early detection and optimise care. The intriguing observation of hypogonadism reversibility prompts exploration of immunosuppression impact. Following LCH treatment, while diabetes insipidus is usually irreversible, a reduced desmopressin requirement can be anticipated.