Inappropriate ADH secretion due to immature ovarian teratoma

Inappropriate antidiuretic hormone secretion syndrome (IADHS) is usually associated with postoperative pain, stress, chest infection, drugs or carcinoma. It is rarely found in patients with gynaecological malignancy. IADHS was found in a 17-year-old girl with an immature ovarian teratoma. Hyponatraemia was persistent and did not respond to fluid restriction therapy before the operation. The plasma sodium level however returned to normal after the removal of the tumour. This is the first reported case of IADHS due to an immature ovarian teratoma or germ cell tumour.