Substance P plasma levels in pregnancy and in various clinical disorders.

Using radioimmunoassay, immunoreactive SP (iSP) has been measured in the plasma of 
162 hospital patients with various disorders and in the plasma of 
67 pregnant women. In pregnancy, iSP was undetectable in 40% women 
as compared to 12% in other hospital patients. The mean iSP 
plasma level in pregnancy was 37.8 +/- 4.6 (SEM) as compared 
to 77.1 +/- 4.9 (SEM) pg/ml in other hospital patients. The 
results support earlier observations based on bioassay, suggesting that the blood 
of pregnant women contains higher concentrations of a SP-inactivating factor. Of 
the hospital patients, elevated levels of iSP were found in patients 
with chronic leukaemia, in one patient with a basaloid carcinoma of 
the anus, and in one patient with toxic liver damage and 
pancreatic insufficiency. No correlation was found between thyroid function and iSP 
plasma levels. ISP plasma levels in various gastrointestinal disorders were similar 
to those found in normal subjects. 