TH and hereditary elliptocytosis: Fischer and Baldessarini64 have proposed that HE could result from the inhibition of catecholamine synthesis due to the high concentrations of phenylalanine which may inhibit the synthesis of dopa from tyrosine by competing with tyrosine (normal substrate) for the enzyme tyrosine hydroxylase and the resultant excess tyrosine is preferentially decarboxylated to form tyramine.