Inappropriate secretion of ADH as a cause of hyponatremia in cystic fibrosis [letter].

After reading "The syndrome of inappropriate antidiuretic hormone [ADH] secretion [SIADH] as 
a cause of hyponatremia in cystic fibrosis [CF]," we are puzzled 
by certain unusual phenomena in the two cases presented. We agree 
that it would be important to recognize the occurrence of ADH 
mediated hyponatremia in CF. We would, though, appreciate the authors' comments 
on the weight losses and the fluid and electrolyte balances early 
in these patients's courses. Also helpful would be information on furosemide 
dosage and any other drugs, such as acetaminophen, which may have 
been given so we can further understand the pathophysiology of these 
two complex patients. - We do not think there was hypovolemia 
in either case. Patient 1 was given only one dose of 
600 mg of acetaminophen on the fourth day of hospitalization during 
recovery. Patient 2 received only one dose of acetaminophen (650 mg) 
at 2 AM on the twenty-first day of admission after recovery. 
Both patients were receiving antibiotics and Patient 2 was receiving digitalis 
as well. The reason for production of ADH remains obscure as 
it is in most cases of SIADH, although it was mentioned 
in the discussion that the transient nature of SIADH in these 
patients with cystic fibrosis would argue against the production of this 
hormone in the lung. 