Plasma L-tryptophan/neutral amino acid ratio and dexamethasone suppression in depression.
We examined the ratio of plasma L-tryptophan (L-TRP) to other neutral amino acids (NAA) in normal controls and depressed patients undergoing a dexamethsone suppression test (DST). The L-TRP/NAA ratio discriminated controls from patients; however, there was no difference in the mean L-TRP/NAA ratio between DST suppressors and nonsuppressors. The cortisol level measured at 1600h postdexamethasone and the L-TRP/NAA ratio were positively correlated. The 1600h postdexamethasone cortisol levels accounted for 24% of the variance of Hamilton Depression Rating Scale ( HDRS ) scores. The inclusion of L-TRP/NAA ratios with 1600h postdexamethasone cortisol levels in a multiple regression equation resulted in an increase in this value and accounted for 65% of the variance in HDRS scores. The finding supports the use of multivariate biological models in depression.
D000328:Adult; D000596:Amino Acids / Q000097:blood; D003866:Depressive Disorder / Q000097:blood* / Q000175:diagnosis; D003907:Dexamethasone; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011569:Psychiatric Status Rating Scales; D012044:Regression Analysis; D014364:Tryptophan / Q000097:blood*
D000596:Amino Acids; D003907:Dexamethasone; D014364:Tryptophan; D006854:Hydrocortisone