Testing the tyrosine/cetecholamine hypothesis of oral contraceptive-induced psychological side-effects: A controlled study on Triphasil (R)

existence of oral contraceptive (OC)-induced psychological side effects tha t might be undetectable by psychometric testing. Methods, Triphasil (R) was administered during six complete menstrual cycles to young never-OC-users. Plasma. Tyr and Trp/Sigma -respective competitor neutral amino acids (NAA) ratio and concentrations of other am ino acids (AA), known to be involved in the functioning of the central nervous system (CNS) and the synthesis of neurotransmitters, in particular, were used as biochemical markers to asse ss this likelihood. Factors known to influence plasma AA concentrations suc h as cortisol and pyridoxal phosphate (PLP, active form of vitamin B-6) bot h modulators of AA intestinal absorption, were examined.. Results: Dietary supply of amino acid substrates (precursors) and blood levels of coenzyme/c ofactor(vitamin B-6 and iron) involved were adequate in both groups and wer e kept constant throughout the treatment. The rise in plasma cortisol, know n to be stimulated under the action of estrogen, was significant (p < 0.05) after the first menstrual cycle and remained higher (although not signific antly) than mean baseline and reference normal values at the end of the 6-m onth OC treatment. Plasma Trp/Sigma -specific competitor NAA ratio remained unchanged whereas Tyr/Sigma -specific competitor NAA ratio was significant ly (p < 0.02) reduced after the sixth artificial menstrual cycle. Conclusio n: Although plasma AA biochemical markers cannot accurately assess CNS acti vity, they seem to be more sensitive than a comprehensive psychometric test ing (MMPI) in assessing OC-induced psychological changes. Copyright (C) 200 1 S. Karger AG,Basel.