Endocrine Abstracts

Introduction: Lymphocytic hypophysitis(LH) is a rare autoimmune endocrinopathy that causes pituitary gland inflammation, resulting in hypopituitarism. Headache is the most common presenting symptom; however, diabetes insipidus (DI) may be the first feature in some patients. Here we report one such case.

Case: a 36-year-old female was referred to the Endocrine clinic with sudden onset of polydipsia, polyuria and nocturia. She also reported amenorrhoea but no galactorrhoea. There was no history of any significant headaches or visual disturbances. Past medical history included autism with anxiety. Fluoxetine and Gabapentin were discontinued by primary care with no improvement in her symptoms. No obvious endocrinopathy was found on clinical examination. The pituitary profile showed hypogonadotropic hypogonadism (FSH 5.8U/l and LH 4.6U/l, oestradiol <92 pmol/l) with slightly elevated prolactin (531 mU/l; NR=102-496). Biochemistry was suggestive of DI with a urine osmolality of 82 mosm/kg and serum osmolality of 298 mosm/kg. Her serum sodium was 142 mmol/l. Desmopressin (DDVAP) 300 mg/day was commenced. A subsequent Pituitary MRI illustrated pituitary stalk thickening and enhancement, suggestive of an inflammatory process. A right-sided 3.5mm pituitary microadenoma was also noted. A water deprivation test confirmed the DI. She was also started on HRT. A screen for causes of pituitary stalk infiltration was performed including CT neck, thorax, abdomen and pelvis; IgG4, serum ACE, AFP, Anti-neutrophil Cytoplasmic antibody (ANCA), and Beta -2 microglobulin. All of which were normal. She was reviewed again after six months. DI was well controlled on DDVAP 200 mg/day. A follow-up pituitary scan revealed a significant reduction in the pituitary stalk thickening. The pituitary microadenoma had not changed. However, she had developed new vertex headaches. Repeat pituitary profile showed a rise in prolactin to 896 miu/l, raising the clinical conundrum as to whether this hyperprolactinaemia is due to the stalk effect caused by LH, or does she have a co-incidental microprolactinoma?

Discussion: LH is an autoimmune condition that involves infiltration of the pituitary gland with T and B lymphocytes. It may also be caused by infiltrative diseases like sarcoidosis, amyloidosis and haemochromatosis. Although confirmation of the diagnosis requires a pituitary biopsy, it is practically not feasible. Hence, diagnosis is based on symptoms, biochemical and radiological findings. In our patient, LH caused the sudden onset of DI and hypogonadism. She has responded well to treatment but should a dopamine agonist trial be considered since she has now developed hyperprolactinaemia in association with new headaches?