Endocrine Abstracts

Case history: 29-year female presented with sudden onset unquenchable thirst, drinking 7 litres fluids/day, waking 4–5 times at night to drink with polyuria and nocturia. She felt lethargic, nauseated with headaches and weight loss. Past Medical History: Hypertension, following Membranous nephropathy in childhood (previously treated with Tacrolimus and steroids). Examination was unremarkable, with full visual fields.

Biochemical Investigations: Confirmed partial hypopituitarism and suggested AVP deficiency. Serum osmolality 294 mmol/kg, Urine osmolality 77 mmol/kg, Sodium 140 m mmol/l, Cortisol 115 nmol/l, TSH 0.36 mU/l, FT4 9.5 pmol/l, IGF1-15.5 nmol/l, Prolactin 1032 mIU/l, FSH 6.1 IU/l, LH 1.3 IU/l, Oestradiol <92 pmol/l, Water deprivation test: Approximately 200 ml/hour dilute urine (urine osmolality average 75 mmol/kg) passed until 1600 hours when Desmopressin was given. 1 hour post DDAVP 2 mg IM, urine volumes reduced to 100 ml/hr and then to 20 mls/hr at 2 hours. Post DDAVP administration, the urine osmolality rose from 76 to 146 mmol/kg at 1 hour, increased to 411 mmol/kg at 3 hours. Weight reduced from 66.5 Kg to 64.4 kg. Plasma osmolality rose from 281 mmol/kg to 295 mmol/kg. Further Investigations to elicit cause of AVP deficiency: Autoantibody screen, IgG subclass, serum hCG and AFP tumour markers: negative. CSF hCG, AFP and cytology unremarkable, extended TB culture negative. Pituitary MRI: Significantly thickened and avidly enhancing infundibular stalk, deviated to right of midline. NM Whole body PET CT: Symmetrical increased tracer uptake within nasopharynx. Nasoendoscopy unremarkable, nasopharyngeal biopsy: Benign follicular lymphoid hyperplasia. Repeat MRI head and whole spine 3 months later: Marked reduction in degree of pathological enhancement of infundibulum.

Management: Started on replacement Desmopressin and prednisolone, then levothyroxine to excellent effect with resolution of all symptoms. Estrogen to be considered at next clinic appointment.

Conclusions: AVP deficiency is a rare disorder affecting 1 in 25000 people. Differentials include granulomatous, inflammatory, autoimmune, and neoplastic disorders. In this age with abnormal imaging there was particular concern about possible neoplasia. The case was discussed at pituitary MDT with results of PET CT and MRI pituitary. They recommended MRI whole brain and spine followed by CSF examination. Follow up MRI showed dramatic resolution of the stalk findings and CSF were normal. A presumptive diagnosis of lymphocytic hypophysitis was made. Primary hypophysitis has a prevalence of 0.2–0.88% and annual incidence 1 in 9 million, with lymphocytic hypophysitis being the most common form of primary hypophysitis (71.8%)