HRT is often a life-long commitment.
You don't do a PCT after HRT, unless medically warranted, you do a PCT after a steroid cycle.
To answer you question, yes, even small amount of 100-150mg of exogenous testosterone will cause complete HPTA shutdown and require some sort of PCT program with SERM usage.
The length of exogenous testosterone use, doses used, androgens used, androgen combinations, gender and genetics will determine how much of PCT is needed.