HCG administration post-cycle is common practice among bodybuilders in the belief that it will aid the natural testosterone recovery, but this theory is unfounded and also counterproductive. The rapid rise in both testosterone, and thus oestrogen due to aromatisation, from the administration of HCG causes further inhibition of the HPTA (Hypothalamic/Pituitary/Testicular Axis - feedback loop discussed above); this actually worsens the recovery situation. HCG does not restore the natural testosterone production.
The typically observed dosing of 2000 to 5000IU every 4 to 5 days causes such an increase in oestrogen levels via aromatisation of the natural testosterone that this has been responsible for many cases of gynecomastia.
From the above discussion it is clear that HCG is best used during a cycle, either to:
1) Avoid testicular atrophy, or
2) Rectify the problem of an existing testicular atrophy.