Endocrine Abstracts

A 27y old woman presented with a 2yr history of secondary amenorrhoea and mild hyperprolactinaemia. CT scan demonstrated an enlarged pituitary gland abutting the optic chiasm. Goldman perimetery was normal and trans-sphenoidal hypophysectomy undertaken. Post-operatively she suffered temporary diabetes insipidus responding well to desmopressin. At endocrine assessment, she was growth hormone deficient, had partial diabetes insipidus and a sub-optimal cortisol response. Desmopressin was commenced but discontinued by the patient when she conceived normally. At 25 weeks gestation, she had thirst and polyuria but despite advice failed to recommence desmopressin. At 27(super)+6(/super) weeks, oligohydramnios, sudden fetal growth restriction and occlusion of single umbilical artery were noted on ultrasound. Intrauterine death was confirmed at 28(super)+2(/super) weeks.

The changes in the relationship between arginine vasopressin concentrations and osmolality in normal pregnancy are well established in rodent models and the human. Diabetes insipidus of pregnancy is well documented. The most likely mechanism is an increased clearance of vasopressin via the action of placental enzyme vasopressinase.

Diabetes insipidus of pregnancy usually presents in the third trimester with symptoms typical of the disease outside of pregnancy. It tends to be more common in primigravida and with male fetuses. It is associated with hepatitic abnormality in liver function. Desmopressin is resistant to breakdown by vasopressinase and is therefore the treatment of choice with a proven safety profile. Failure to treat can have serious repercussions in pregnancy despite the presence of an intact thirst mechanism. There are case reports linking oligohydramnios to diabetes insipidus of pregnancy. Indeed, some studies have recommended desmopressin as a treatment for oligohydramnios even in the absence of diabetes insipidus. This case illustrates the importance of monitoring and treating this disorder in pregnancy and the potential problems.