We present formal models and efficient synthesis algorithms for threshold gates of Generalised Threshold Gate (GTG) and Multi Threshold Threshold Gate (MTTG) structures. For GTG synthesis our method does not require to calculate thresholds, that separate function onset and offsets, which greatly simplifies and speeds up the synthesis algorithm. For MTTG we propose a novel synthesis method that determines structure and circuit parameters efficiently. As complexity of MTTG circuit increases with number of thresholds we have developed a dedicated heuristic for efficiently determining the number of required thresholds. The number of resulting thresholds is smaller compared to the number of thresholds calculated using other methods.