Endocrine pastest learnings

Question 1

Describe the differences in results following a water deprivation test in
- normal
- Cranial diabetes insipidus
- nephrogenic diabetes insipidus
- Psychogenic polydypsia

Answer 1

Normal will have a normal plasma osmolality to start and urine osmolality remain high after desmopressin.

Cranial DI will have a high plasma osmolality to start. low urine osmolality after deprivation. Following desmopressing the urine osmolality will be high

Nephrogenic DI will have a high plasma osmolality to start. The urine osmolality will be low and remain low post desmopressin as the kidneys do not respond to
ADH.

In psychogenic DI the plasma osmolality will be low. The urine osmolality will remain low post test.

Question 2

What is nephrogenic diabetes insipidus?

Answer 2

Decreased ability to concentrate the urine due to resistance to ADH in the kidney

Question 3

What is the radiological hallmark of a cranipharyngioma?

Answer 3

Suprasella calcified cyst