A 30 year old gentleman presented with long standing symptoms of polyuria and polydypsia and poor libido. On examination he was short (155 cm), weighed 108 kg with a body mass index of 45.1. Investigations revealed normal Blood Glucose, renal function, liver function and calcium. Water deprivation test confirmed the diagnosis of Cranial Diabetes Insipidus. He was started on DDAVP tablets 100 micrograms twice daily. Further tests showed a normal IGF-1, synacthen test and prolactin. His FT4 was 9.8 pmol/L (1023) with a TSH of 1.14 mU/L, rising to 8.91 after TRH. His serum testosterone was 1.7 nmol/L (1040), basal FSH of 0.3 U/L and LH of 0.1 U/L with no significant rise after LHRH. MRI brain revealed congenital midline defects and dysgenesis of the Corpus Callosum, with the anterior portion present but the posterior portion was absent. There was also a trans-sphenoidal encephalocele, with elongation of the anterior third ventricle and stretching of the pituitary gland through the defect.
Clinical diagnosis of hypopituitarism with midline brain abnormalities was made. His symptoms have dramatically improved on replacement thyroxine, testosterone and DDAVP. In congenital midline brain malformation there is a spectrum of disordered neuro-anatomy associated with variable pituitary function. However initial presentation of congenital midline malformation in adult life is rare. This case emphasizes the need to fully assess the endocrine function in patients with midline structural defects. Radiologists should consider endocrine referrals in all patients in whom midline congenital malformations are detected.