  Two-loop threshold corrections for both the strong coupling constant and
Yukawa couplings of heavy SM fermions are considered in the context of Minimal
Supersymmetric Standard Model (MSSM). With the help of the well-known SOFTSUSY
code the dependence of the corrections on universal MSSM parameters is
analyzed. For a consistent study of the influence of the corrections on SUSY
mass spectrum three-loop renormalization group equations are implemented. A
particular scenario (SPS4) is considered and the shifts of the particle masses
due to contributions of different threshold corrections are presented.
Additionally, the impact on certain forbidden regions of the parameter space is
studied.
