Initial Labs:
WBC: 7.6,
Hb: 12.3,
Platelets: 258.
MCV 85
PT/PTT normal.
CT head: Cortical atrophy is seen.
Lobulated sellar mass 1.3 x 1.5 x 2.2 cm
Na 119,
K 3.6,
CO2 22,
Chloride 88,
BUN 8,
creatinine 0.8,
glucose 109


What is your interpretation of his serum sodium, what additional tests do you need? (besides urine lytes, see below)

S. Osmolality: 266 (280-295),
Urine osmolality 150s,
Urine Na 15. Urine specific gravity 1.004.

U Na is low and he looks dry (clinically), Therefore, he has hypovolemic hyponatremia.
The urine osmolality is low in order to excrete free water load due to the low serum osmolality.

What are all the potential causes of hyponatremia in this patient?

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