I'll include my reply from over at EM:
Gonadorelin may work
with TRT—producing endogenous LH and FSH—if you add a SERM. But it's not clear if even daily injections would be enough.
Kisspeptin is untested in this capacity, as far as I know. It's an interesting peptide, as its suppression in TRT could be detrimental to us, which may also
be the case with gonadorelin/GnRH. For kisspeptin alone to stimulate production of gonadotropins it must first overcome negative feedback at the hypothalamus to produce endogenous GnRH. If this does happen then you still need a SERM to allow the endogenous GnRH to stimulate the pituitary. The hypothalamus has negative feedback from both androgens and estrogens. If we're lucky, all of this negative feedback is upstream of kisspeptin production, so that exogenous kisspeptin would lead to GnRH production. I'm not sure if infrequent injections of kisspeptin would be sufficient for this; it does have a short half-life.
Bottom line: I think you must use a SERM to get either of these possible hCG replacements to do something useful while on TRT. I've shown that gonadorelin is viable, though not necessarily practical. The situation with kisspeptin is less clear.