Endocrine Abstracts

Ectopic posterior pituitary is a rare congenital pituitary anatomical defect of complex inheritance resulting in heterogeneous clinical and radiological phenotypes. Presentation is primarily in paediatric patients with growth and development effects. We present a rare adult presentation patient. A 33 year old male presented with low libido and paucity of facial hair. Previous medical history was limited to a left undescended testis. He took no regular medications, anabolics or recreational substances. Examination confirmed weight 112.7 kg, BMI 36, normal secondary sexual characteristics with testicular volume 25 ml right and 20 ml left. Basal endocrine investigations at 09:00 h: cortisol 528 nmol/l, ACTH 71.5 ng/l, fT4 10.3 pmol/l, fT3 6.4 pmol/l, TSH 4.03 mU/l, testosterone 5.0 nmol/l, free testosterone 151 pmol/l, bioavailable testosterone 3.3 nmol/l, FSH 2.2 IU/l, LH 1.7 IU/l, prolactin 812 mU/l, IGF-1 13 nmol/l, plasma osmolality 291 mmol/kg and urine osmolality 836 mmol/l (post 8 h water deprivation). Dynamic endocrine testing: insulin tolerance test confirmed normal cortisol and growth hormone responses. MRI pituitary demonstrated a hyperintense lesion along the pituitary stalk consistent with ectopic posterior pituitary. Further investigations: plasma AFP 5 kU/l, HCG <1.0 IU/l and CSF AFP<0.5 kU/l, ACE 18 U/L. Treatment with cabergoline 0.25 mg once weekly for 6 months normalised prolactin (219 mU/l) with minimal effect on testosterone (7.9 nmol/l, free testosterone 220 pmol/l and bioavailable testosterone 5.39 nmol/l) with no symptomatic improvement. A GnRH test suggested an impaired gonadotrophin response. Treatment with testosterone supplements resulted in alleviation of his symptoms.