Short answer: hCG is an FDA-approved injection that acts like LH directly on the testes.1 Kisspeptin works further up: it signals the brain to release GnRH, which then raises the body's own LH and FSH.2 Kisspeptin is not FDA approved, and FDA lists kisspeptin-10 as a compounding safety concern.3 Most human kisspeptin studies are short and small.
| hCG (Novarel, Pregnyl) | Kisspeptin (kisspeptin-10, kisspeptin-54) | |
|---|---|---|
| Mechanism | Acts on the LH receptor in the testes1 | Stimulates GnRH release, which raises LH and FSH from the pituitary2 |
| Approval status | FDA approved, including for selected hypogonadotropic hypogonadism in males1 | Not FDA approved. Kisspeptin-10 is on FDA's 503A Category 2 list (safety risks) since September 20233 |
| Dosing schedule | Label (male hypogonadotropic hypogonadism): for example 4,000 USP units 3 times a week for 6 to 9 months, then 2,000 units 3 times a week for 3 months1 | Studied mostly as single doses or infusions into a vein; one 2026 study used daily 8-hour infusions under the skin for 12 days4 |
| Route | Injection into muscle only, per the label5 | Into a vein in most studies; under the skin in a few64 |
| Half-life | Not stated on the Novarel or Pregnyl labels. Dose Track uses about 29 hours, from the Ovidrel label7 | Short; studies use continuous infusions to keep levels up. No measured half-life under the skin |
| Effect on LH in men | Replaces the LH signal; the body's own LH is not raised | Kisspeptin-10 into a vein raised LH from 4.1 to 12.4 IU/L at 30 minutes2 |
| Effect on testosterone in men | Raises testosterone made by the testes | A 22.5-hour infusion raised testosterone from 16.6 to 24.0 nmol/L2 |
| Sex differences | Label dosing differs by indication | Kisspeptin-10 did not raise LH in women in the early follicular phase, but did in men6 |
| Notable warnings | Label states hCG is not effective for obesity; precocious puberty when treating cryptorchidism1 | No label. FDA cites possible immune reactions and limited safety data3 |
The chain runs brain (GnRH) to pituitary (LH and FSH) to testes (testosterone and sperm). hCG skips the first two steps and acts like LH on the testes.1 Kisspeptin acts at the top: in men it raised LH within 30 minutes and, given continuously, increased how often LH pulses came.2 Because it works through the body's own system, a working pituitary is needed for kisspeptin to have an effect.
These are small, short research studies, mostly with infusions in a clinic. None tested kisspeptin as a long-term treatment, and none compared it with hCG.