  Extensions of the MSSM generically feature gauge singlet Higgs bosons. These
singlet Higgs bosons have tan(beta)-enhanced Yukawa couplings to down-type
quarks and leptons at the one-loop level. We present an effective Lagrangian
incorporating these Yukawa couplings and use it to study their effect on
singlet Higgs boson phenomenology within both the mnSSM and NMSSM. It is found
that the loop-induced couplings represent an appreciable effect for the singlet
pseudoscalar in particular, and may dominate its decay modes in some regions of
parameter space.
