Plasma amino acids, cortisol, prolactin, oestrogen, progesterone, thyr
oxine, thyrotropin, folate, vitamin B-12, urinary biopterins, and neop
terins were measured in 33 male and 30 female patients with DSM-III-R
major depression. The results were compared with those obtained in 32
male and 38 female normal controls. Male depressive patients had signi
ficantly lower plasma levels of tryptophan, cysteine, thorine, ornithi
ne, tryptophan/large neutral amino acids (LNAA) ratio, folate, vitamin
B-12, oestrogen, and thyroid-stimulating hormone levels than normal c
ontrols. Male depressive patients, however, had significantly higher p
lasma levels of methionine and thyroxine than normal controls. Female
patients had fewer significant differences with lower plasma levels of
histidine, ornithine; glutamine, and tryptophan/LNAA ratio, and highe
r plasma levels of arginine, cortisol, and prolactin than normal femal
e controls. The results are consistent with those obtained in Western
populations and support the notion of a universal biologic substrate f
or depression.