Tryptophan and tyrosine availability and oral contraceptives
Møller, S.E.
Lancet 2(8140): 472
1979
ISSN/ISBN: 0140-6736 PMID: 89532 DOI: 10.1016/s0140-6736(79)91526-5Document Number: 442243
The effects of oral contraceptives on plasma concentrations of amino acids was studied in order to determine metabolically why depression appears as an adverse side effect in women taking oral contraceptives. Brain catecholamines, including serotonin, noradrenaline and dopamine, are synthesized from the precursor amino acids tryptophan and tyrosine. Catecholamine deficiency may be related to depressive symptoms and thus, lowered plasma concentrations of amino acids may contribute to depression. Plasma concentrations of amino acids were compared in 9 women taking birth control pills and 11 drug-free controls. No significant differences were found in levels of tryptophan, valine, isoleucine, leucine or phenylalanine; however, levels of tyrosine, as well as the plasma ratio of tyrosine to 5 competing amino acids, were significantly decreased in oral contraceptive users. These data indicate that the availability of tyrosine to the brain is decreased in these women, possibly resulting in decreased formation of catecholamines and depression.