Peptides for testosterone

How do these peptides relate to testosterone?

Kisspeptin drives the release of GnRH, the hormonal signal that starts the cascade leading to testosterone production; mutations in its receptor, GPR54, cause absent puberty in humans [1]. Gonadorelin is a synthetic form of GnRH itself, one step further upstream from testosterone; the human product Factrel, approved in 1982, is listed in Drugs@FDA as discontinued [3]. Testosterone replacement therapy works on testosterone directly; testosterone is a steroid hormone, not a peptide.

Are these peptides FDA-approved for raising testosterone?

Only hCG, sold as Pregnyl, is FDA-approved, indicated for hypogonadotropic hypogonadism in males and specific fertility uses; the label states hCG "has not been demonstrated to be effective adjunctive therapy" for obesity [2]. Kisspeptin-10, a related but distinct fragment from the kisspeptin used in research, sits in FDA's Category 2 compounding list over immunogenicity risk [4].