Renal Endocrine Case Study
The Endocrine Society
A 32-year-old woman is self-referred for evaluation of chronic thirst, polydipsia, and polyuria. The
symptoms have been present for many years and seem to increase during her pregnancies. Several
years before, she consulted another physician who “tested my sugar,” performed a dehydration test,
and told her not to worry because she simply “drank too much.” She is otherwise healthy and takes
no drugs. She was adopted at an early age and knows nothing of her biological family.
Upon physical examination, a CBC, and a chemistry profile are found to be within normal limits.
However, her 24-hour urine volume is 6.5 liters and urine osmolarity are 125 mOsM, respectively. A 4
hour water deprivation test increases her urine osmolarity to 465 mOsM and plasma sodium to a
maximum of 141 meq/L, after four hours at which time the test is suspended due to weight loss of
greater than 3 kg. The test also increases her thirst. Plasma ADH levels were not measured.
Injection with desmopressin did not increase urine osmolarity. As the attending physician you need to
determine the next test to be done to figure out what is causing the chronic thirst. Here is the list of
choices:
A. Assess the response of urine osmolality to another injection of desmopressin
B. Order an MRI of the brain before and after gadolinium infusion
C. Measure plasma vasopressin before and after an infusion of hypertonic saline via IV
D. Start treatment with desmopressin and reevaluate the symptoms in two weeks
E. Order a psychiatric evaluation
Type out your answers to these questions on a separate document and include references at the end
Part A Define the following terms:
Chronic Thirst
Polydipsia
Polyuria
Diabetes Myelitis
Diabetes Insipidus
Desmopressin
Gadolinium
IV hypertonic saline
Part B Next answer the following questions
1. Look online for possible pathological conditions that cause polyuria and polydipsia as
symptoms. List at least 5. (Note the tests that have already been conducted and those that
are contemplated for clues as to what might be causing these symptoms and which the
doctors are considering.)
2. Look online for the results of a normal CBC test. What CBC test result would you expect to
see elevated with someone who is chronically dehydrated? Are there any causes of
polyuria/polydipsia that may be detected using a CBC test?
3. Look up online the results of a normal Blood Chemistry Panel. Are there any causes of
Polyuria/polydipsia that could be ruled in/out with a blood chemistry panel?
4. What are the 4 types of diabetes insipidus?
5. What is a normal value for 24 hr urine osmolality and volume? Are the patient values normal?
CS6 ‘21 2
6. Describe the “fluid deprivation test”. How is it conducted? Why did the doctor order it (what
was the doctor looking for)? How does it differ from a dehydration test?
7. What are the normal values for urine osmolality/osmolarity (or SG) and plasma sodium after
the fluid deprivation test? Are the patient values in the expected range for someone without
diabetes insipidus?
8. What is the main stimulus for the release of vasopressin/ADH?
9. How can you differentiate between each type of diabetes insipidus by conducting each of the 5
possible next tests listed above? To answer this, you will need to look up each of the proposed
choices to find out why they are being considered. Tell me about each test/choice. What is the
reasoning behind each choice? What are the predicted outcomes/results expected for each of
the tests and determine why you would either choose or reject each?
10.LAST What choice (from the list above) will you make now that you have more information?
11.Provide a list of your references
Please read the following statement and include it with your report: “I understand that learning how
to apply concepts to real problems in physiology is a valuable skill to have. Therefore, I have not
searched the internet for answers to these specific questions and have not used “homework
helper” sites. I found the information to answer these questions by searching for specific terms
and concepts and generated my own answers based on this information. When working with my
peers, we collaborated but did not copy from each other.
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