Endocrine Abstracts

A 48-year-old male presented with headache, cough and recurrent nose bleeds. Clinical examination showed saddle shape nose deformity. His past medical history included primary hypothyroidism diagnosed at the age of 10 years, was taking levothyroxine. His brother had a Rathke’s cleft cyst, surgically removed. His blood test were as follows: Sodium 125mmol/l, TSH 0.10mU/l, free T4 10.2pmol/l, freeT3 2.6pmol/l, cortisol < 28nmol/l, prolactin 240mU/l, FSH 1.8U/l, LH 0.3U/l. He was commenced on prednisolone 3mg and continued on levothyroxine 125mg. Initial CT Head showed suprasellar lesion with right sided mastoiditis. MRI pituitary showed a centrally cystic sellar and suprasellar lesion with peripheral enhancement, thickening of the pituitary stalk and abnormal signal in retro-chiasmatic tracts. Visual field (VF) assessment showed a left temporal superior visual field defect with normal right vision. The differential diagnosis was cystic macroadenoma, atypical hypophysitis or previous apoplexy. Pituitary MDT discussion advised to send off a vasculitis screen that showed weakly positive c-ANCA, PR3 antibody positive at 7.3 IU/ml (normal range upto 1.9). All other antibodies were negative including negative TB Elispot. A repeat VF assessment however, showed progression to bitemporal quadrantanopia. A diagnosis of ANCA-associated vasculitis was established and prednisolone was increased to 60 mg. A pituitary biopsy was considered if no improvement in visual fields. A repeat MRI after 6 weeks showed interval reduction in size with central cystic cavity collapsing down thus confirming likely an inflammatory process responding to glucocorticoid treatment. Once started on high-dose steroids, he reported polyuria and polydipsia with normal blood glucose levels. Awater deprivation test was consistent with a diagnosis of cranial diabetes insipidus which was managed with desmopressin. He was commenced on rituximab 1g, two weeks apart followed by a gradual reduction of prednisolone to meintenance dose of 3mg. Although he was eventually found to have hypogonadotrophic hypogonadism however wasn’t started on testosterone replacement due to absence of any symptoms. Subsequently, he showed good clinical and radiological improvement and was able to return to work. On repeat MRI further reduction in size of pituitary gland was noted, normal thickness of stalk and uniform contrast enhancement. He remains under regular clinical follow up with a plan to continue 6-monthly rituximab infusions for remission maintenance and periodic pituitary MRI surveillance. This case posed a diagnostic challenge given the absence of many systemic features of vasculitis. In addition, it highlights the delayed diagnosis of posterior pituitary dysfunction which was unmasked by the high dose steroids. It also emphasizes the importance of the MDT approach to manage such cases.