We present a case of disseminated intracranial germinoma presenting with diabetes insipidus and evolving panhypopituitarism.
A 17 year-old man presented with three month history of frequent nocturia, polydipsia associated with lethargy, weight loss and erectile dysfunction with normal secondary sexual characters. His initial investigations revealed a picture of hypogonadotropic hypogonadism associated with diabetes insipidus and was commenced on testosterone replacement and intranasal desmopressin
Testosterone : <0.7 nmol/L (8.0-26.0)
FSH : 0.4IU/L (1.4-18)
LH : 0.6IU/L
Cortisol : 405 nmol/L
MRI of the pituitary gland showed a normal pituitary gland with no stalk thickening and no mass effect on the hypothalamus. An Incidental finding of a septated pineal cyst, measuring 14mmx10mmx12mm with enhancing septations was also noted. A transasal pineal gland biopsy was inconclusive. A second biopsy under sterotactic guidance showed a calcified arachnoid cyst with no evidence of germ cell tumor.
He later developed secondary adrenal insufficiency and central hypothyroidism.
Cortisol 25 nmol/L
ACTH 1.6 pmol/L (<20.0)
TSH 2.019 mIU/L (0.300-4.000)
fT4 : 9.1 pmol/L (11.5-22.7)
fT3 : 2.8 pmol/L (3.5-6.7)
A repeat MRI revealed pituitary infundibular thickening and abnormal enhancement of the infundibulum and hypothalamus. The pineal tumor appeared solid and had increased in size. With the suspicion of lymphocytic hypophysitis, he was commenced on high dose prednisolone 50 mg daily ffor 4 weeks with no improvement in symptoms
He later developed a bitemporal hemianopia and an MRI revealed an increased pineal tumor measuring 18x17x17 mm with extension into adjacent brain parenchyma, extending to lateral ventricle, and suprasellar extension involving the optic chiasm. He underwent a craniotomy and pineal gland biopsy which confirmed a disseminated germinoma of the pineal gland.