Endocrine Abstracts

A 16 year old boy presented to his GP with a two month history of polyuria and polydipsia. He was reviewed by his GP and diabetes mellitus was ruled out. At the time of presentation three months later, he had a three week history of headache and vomiting. His glasses prescription had changed and he had increasing diplopia. The optician found bilateral papilloedema and he was referred to the eye clinic for further assessment. Due to abnormal gaze palsies, he was admitted to the neurosurgery ward. On examination, blood pressure 131/85 mmHg. There were upward and lateral gaze palsies with convergence retraction nystagmus. He underwent CT head which showed a 3 cm soft tissue mass engulfing the pineal gland and a smaller hyperdense mass in the infundibular recess of the third ventricle associated with hydrocephalus. MRI confirmed these findings and the smaller mass is inseparable from the pituitary stalk. During his admission, it was noted he was passing excessive amount of urine and drinking 4-6l of fluids daily. He was referred to Endocrinology for work up for diabetes insipidus (DI). He had completed his pubertal development and testes volume was 20 mls bilaterally. Serum osmolality was 303 mmol/kg (275–295), urine osmolality 136 mmol/kg and urine sodium 23 mmol/l. Blood tests showed normal sodium level, FT3 2.8 pmol/l(4–7), FT4 8 pmol/l (10–25), TSH 2.71 mu/l (0.51–4.94), prolactin 1011 mu/l (45–375), IGF-1 17.9 nmo/l (22.5–53.8), testosterone 28.5 nmol/l(4.1–32.9), undetectable LH and FSH. Short synacthen test was abnormal. Testosterone level was inappropriately normal for low levels of LH. Further tests revealed alpha fetoprotein 391 kU/l (0–10), B-HCG 19 u/l(0–5). CSF cytology revealed no malignant cells but raised AFP 982 microg/L (0–3) and HCG 79 IU/L (0–2). The biopsy is in keeping with a germinoma. He was confirmed to have a pineal HCG secreting germ cell tumour causing panhypopituitarism. He was commenced on hydrocortisone, levothyroxine and desmopressin. He is now under the care of oncology for chemotherapy and radiotherapy. Intracranial germinomas account for 0.5–2.0% of all intracranial tumours. Suprasellar involvement will cause endocrinopathies with DI being the most common presenting feature. Most HCG secreting germ cell tumours are diagnosed by young adolescence therefore present with precocious puberty. In older patients, symptoms depend on location of tumour with pituitary hormone deficiency. This is an unusual case with low gonadotropins but normal testosterone which is likely due to stimulating effect of B-HCG on LH receptors.