Methods of forming a feedthrough using a mold that defines a cavity when closed and includes one or more cores configured to move in and out of the mold cavity. The methods include injecting non-electrically conductive powder injection molding (PIM) feedstock into the mold cavity to form an insulative body around a portion of each of the cores disposed in the mold cavity, removing each of the cores from the insulative body to form one or more core cavities in the insulative body, injecting electrically conductive PIM feedstock into the core cavities to form one or more conductors in the core cavities, respectively, and sintering the insulative body and the conductors to form the feedthrough.