Pituitary Case: 28-year-old Woman with Excessive Thirst and Urination

00:01 Let's go on to another case.

00:03 An otherwise healthy 28-year old woman who is eight months postpartum comes to see you because she has excessive thirst and urination.

00:11 She still has amenorrhea since giving birth.

00:15 Her vital signs are normal and physical exam is normal other than dry mucous membranes.

00:21 The serum glucose is 90 milligrams per deciliter, sodium 146, calcium 8.1, and measured urine output 4 liters per day.

00:30 What is the most likely diagnosis? Here, we have a postpartum patient.

00:38 She has secondary amenorrhea in addition to excessive thirst and excessive urination.

00:44 This is manifesting with evidence of dehydration.

00:48 She also has elevated urine output.

00:51 Clinically, she most likely has central diabetes insipidus, and you need to check a simultaneous urine and serum osmolarity.

01:00 Excretion of more than three liters of urine per day is defined as polyuria.

01:05 Diagnosis should be made clearly using the above information.

01:09 However, a water deprivation test may be beneficial if the diagnosis is unclear.

01:15 In this patient, she has a normal sodium level.

01:19 If the sodium is on the higher side, always use caution when doing a water deprivation test as the patient's serum sodium may rise extremely high and cause clinical symptoms.

01:33 The main thing driving the normal sodium in this particular patient’s case is that with her central diabetes insipidus and her increased thirst, she's able to take in enough fluid to be able to maintain a normal serum sodium level.

01:50 Serum osmolarity greater than 295 milliosmols per kilogram with an inappropriately dilute urine will give you the confirmation of the diagnosis or low urine osmolarity or urine to serum osmolarity ratio of less than two.