Endocrine Abstracts

A 37-year-old female, referred by gynaecologist with low prolactin and free T4 after work up for secondary amenorrhea despite removal of contraceptive coil 18 months ago. Her only daughter was born seven years ago with no complications. Patient admitted to have tiredness and dizziness for a few years but denied headache or visual symptoms. Pituitary hormone profile confirmed secondary hypothyroidism, secondary hypogonadism, low prolactin, low IGF-1 level but normal adrenal axis. MRI revealed pituitary tumour measuring 6×4×2 cm compressing the optic chiasm. Initial visual assessment demonstrated bitemporal hemianopia and preserved visual acuity. She developed severe headaches and vomiting within a few days and repeat visual assessment suggested rapid worsening of vision. Repeat imaging showed no evidence of pituitary apoplexy and she underwent urgent transcranial surgery. The surgery was challenging as tumour was adherent to hypothalamus, walls of third ventricle and optic chiasm.Post-surgery, she developed diabetes insipidus and symptoms of hypothalamic dysfunction including impaired thirst, hyperphagia, impaired temperature regulation and anterograde amnesia. Treatment of diabetes insipidus with impaired thirst was challenging even with strict fluid allowance and desmopressin. Patients with diabetes insipidus and intact thirst drink appropriate quantity of fluids to replace urine losses driven by hypothalamic thirst mechanisms. While on desmopressin, one must drink to thirst. Achieving optimal fluid and electrolyte balance becomes challenging if thirst perception is impaired. She was started on oral desmopressin 100 microgram twice a day with strict fluid allowance of 750 ml to 1250 ml every 12 hours. She had strict monitoring of input and output, serum electrolytes and serum and urine osmolality. Our patient had predominant polydipsia despite desmopressin intake, no polyuria and low serum sodium. Despite regular monitoring, serum sodium levels fluctuated as she was spotted drinking water from taps of the toilet. It is further difficult to achieve a satisfactory fluid balance at home after discharge even with family support. This case outlines the difficulties in management of patients with diabetes insipidus and unreliable thirst perception. Frequent monitoring of biochemistry, accurate recording of fluid input and output, an acceptable fluid allowance, strict compliance with prescribed desmopressin, good communication with patient’s primary care physician, carer supervision and family support are essential.