HCG is a glycoprotein hormone with recognized, FDA-approved uses in fertility medicine and in certain hormonal conditions. This page describes those roles and separates them from unproven or debunked marketing claims.
The short answer
HCG's benefits are real, narrow, and reproductive. It works because it is a near-functional twin of luteinizing hormone: it binds the same receptor and drives the same gonadal steroidogenesis, so an injection can substitute for a pituitary LH signal that is missing or mistimed. That single mechanism underwrites everything it is approved for — triggering ovulation, restarting testicular function, and prompting testicular descent in certain children.
It also explains what HCG cannot do. Nothing about LH-receptor activation touches fat metabolism, and the weight-loss claim attached to HCG has been tested and rejected — by meta-analysis and, unusually, by the drug's own FDA-approved labeling.
The three labeled indications
The Pregnyl label lists exactly three approved uses (Pregnyl, DailyMed):
- Prepubertal cryptorchidism not due to anatomical obstruction — the label frames HCG as inducing testicular descent in situations where descent would have occurred at puberty anyway, which also makes it a way to predict whether orchiopexy will eventually be needed. Therapy is usually instituted between ages 4 and 9, and the label notes that in some cases the response is temporary.
- Selected cases of hypogonadotropic hypogonadism in males — hypogonadism secondary to pituitary deficiency, not primary testicular failure.
- Induction of ovulation and pregnancy in an anovulatory infertile woman whose anovulation is secondary rather than due to primary ovarian failure, and who has already been appropriately treated with gonadotropins.
The qualifiers matter more than the headings. Each indication specifies a population where the pituitary signal, not the gonad, is the failing part. HCG supplies a missing message; it cannot substitute for a gonad that cannot respond.
On the female side, the label describes the physiology plainly: the mid-cycle LH surge triggers ovulation, and HCG can substitute for LH in that function. That is the basis of the "trigger shot" before intercourse, insemination, or oocyte retrieval.
What gonadotropin therapy achieves in men
The male-fertility benefit has been quantified. A 2025 systematic review and meta-analysis pooled 41 studies covering 1,673 men with pathological gonadotropin deficiency (mean age 25) (PMID 39445789):
- Mean sperm concentration after a median 18 months of gonadotropin treatment was 11.6 million/mL (95% CI 8.4–14.9).
- Any sperm at all appeared in 78% of patients; 55% exceeded 1 M/mL, 36% exceeded 5 M/mL, 24% exceeded 10 M/mL, and 15% exceeded 20 M/mL.
- Combined hCG plus FSH beat hCG monotherapy on mean sperm output and on every threshold measured — even though testosterone and testicular-volume increases were similar between the two.
- Men with congenital hypogonadotropic hypogonadism responded less well than those with acquired hypopituitarism.
The authors' own framing is the honest one: gonadotropin treatment induced spermatogenesis in most men, but the sperm outputs typically needed for natural conception were reached far less often. "It works" here is a probability distribution, not a switch.
The TRT-adjunct question
The most-searched off-label use is preserving testicular function during testosterone therapy. The rationale is sound in outline: exogenous testosterone suppresses pituitary LH, intratesticular testosterone collapses, and spermatogenesis — which requires that local testosterone, not the serum level — stops. A review of the literature on exogenous testosterone and male infertility identifies hCG therapy, including low-dose hCG given alongside testosterone, among the strategies used to protect the testis, and notes that most men recover normal sperm production within a year of discontinuing testosterone regardless (PMID 26813847).
This sits outside the label. It is a clinical decision made by a prescriber weighing fertility goals against hormonal side effects, not a protocol with an approval behind it.
The "HCG diet" claim
HCG is marketed for weight loss as part of the 1950s-era Simeons protocol, which pairs injections with roughly 500 calories a day. A criteria-based meta-analysis traced 8 controlled and 16 uncontrolled trials and scored each for methodological quality on a 100-point scale. Scores ran from 16 to 73, indicating generally poor design. Among the 12 studies scoring 50 or above — all of them controlled — exactly one reported HCG as a useful adjunct. The conclusion was that there is no scientific evidence HCG produces weight loss, fat redistribution, reduced hunger, or improved well-being (PMID 8527285).
The Pregnyl label reaches the same verdict in its own capital letters, stating that "HCG HAS NOT BEEN DEMONSTRATED TO BE EFFECTIVE ADJUNCTIVE THERAPY IN THE TREATMENT OF OBESITY" and that it "HAS NO KNOWN EFFECT ON FAT MOBILIZATION, APPETITE OR SENSE OF HUNGER, OR BODY FAT DISTRIBUTION." Weight lost on the protocol is attributable to the 500-calorie diet, which is also where the risks sit.
Sport & Anti-Doping Warning
Human chorionic gonadotropin (hCG) has been misused by male athletes as part of steroid cycles to stimulate endogenous testosterone and is specifically prohibited in male competitors.
- >Scientific discussion of hCG misuse and detection in athletes
- >Coverage of recent professional sport suspensions for hCG positives
In anti-doping rules, hCG is banned in males and often treated as a marker of attempted steroid cycle manipulation rather than a benign fertility drug.