HCG: Side Effects

Safety Notice#

The safety profile of HCG in humans has not been established through controlled clinical trials. The information below is derived primarily from animal studies and should be interpreted accordingly.

Documented Adverse Effects#

We synthesized adverse effects of human chorionic gonadotropin (hCG) from animal experiments and human clinical and case-report evidence, emphasizing frequency and severity when available.

Animal studies

• Mouse developmental toxicity with hCG exposure: In C57Bl/6J and B6CBA/F1 mice, hCG alone (5–20 IU) for ovulation induction and PMSG+hCG for superovulation increased abnormal preimplantation embryos and reduced blastocyst formation; postimplantation losses rose to 35–43% versus 8% in controls, live fetuses per pregnancy decreased (3.9 ± 0.9 vs 7.7 ± 0.3), mean fetal weight was reduced by ~51% (0.50 g vs 0.98 g), and skeletal ossification was delayed. Pregnancy rate was lower with hCG (71%) than controls (91%). Severity: substantial developmental toxicity affecting viability and growth; quantitative effects reported above.

Human evidence

• Controlled ovarian stimulation (approved/clinical use): In a randomized, placebo‑controlled trial of recombinant hCG (CG beta) added to follitropin delta during a long GnRH‑agonist protocol (n≈619), the incidence of ovarian hyperstimulation syndrome (OHSS) across CG‑beta dose groups was 2.0–9.3% and headache 3.0–6.5%; injection‑site reactions were mostly mild. Treatment‑induced anti‑CG‑beta antibodies occurred in 1–4% with very low titres and no neutralizing capacity. Severity: adverse events were generally mild–moderate; no clear increase in serious adverse events attributable to CG beta was detected.
• Misuse for weight loss (unapproved): Case reports describe serious thrombotic events including pulmonary thromboembolism (PTE) and ischemic stroke in individuals using low‑dose hCG (e.g., 100–200 IU/day; index case ≈125 IU/day subcutaneously). Reported accompanying symptoms include flushing, breast swelling, and minor vaginal bleeding. Causality for adverse effects in one case was assessed as “probable” by Naranjo. Frequency: case‑level evidence without population denominators; severity: serious/life‑threatening in thrombotic events. Additional reports of the so‑called “HCG diet” note increased anxiety scores versus placebo in one trial and laboratory changes (decreased WBC, lipids, proteins, hematocrit, BUN; possible uric acid increases), with delayed menses reported; many laboratory changes are plausibly attributable to severe caloric restriction rather than hCG per se. Frequency: anxiety increase reported with group means; other outcomes largely descriptive without standardized rates; severity: typically mild–moderate for symptoms/labs, but thromboembolism represents a serious adverse event signal.

Key takeaways with frequency/severity

• Animal models demonstrate dose‑context‑dependent developmental toxicity with hCG exposure, including increased embryonic abnormalities, higher postimplantation loss (≈35–43%), and severe fetal growth/ossification delays.
• In clinical ovarian stimulation with recombinant hCG, common adverse effects include OHSS (2.0–9.3%) and headache (3.0–6.5%); injection‑site reactions are typically mild, and treatment‑induced antibodies are uncommon (1–4%) and non‑neutralizing.
• In unapproved weight‑loss use, serious thrombotic events (PTE, stroke) have been reported in case reports at low daily doses; frequency cannot be estimated from case data, but severity is high. HCG‑diet studies report increased anxiety and various laboratory changes, though many changes likely reflect the extreme calorie restriction rather than hCG itself.

Structured summary (evidence matrix)

Animal Study Safety Data#

Formal contraindications

• Pregnancy: hCG is contraindicated due to risks of virilization/teratogenicity and ectopic pregnancy concerns.
• Hormone‑dependent tumors: Contraindicated in androgen/estrogen‑dependent malignancies (e.g., prostate or breast cancer) because hCG’s LH‑like activity elevates sex steroids.
• Undiagnosed ovarian enlargement/ovarian cysts: Avoid in unexplained ovarian enlargement or active ovarian cysts.
• Precocious puberty: Contraindicated because hCG can precipitate or worsen premature sexual maturation.
• Uncontrolled endocrine disorders: Avoid until controlled in thyroid, pituitary, or hypothalamic disease; prolactinoma/pituitary tumors are contraindications in referenced tables. hCG’s thyrotrophic activity can alter thyroid indices.

Known interactions and clinically relevant co‑management

• Documented drug–drug interactions: Major clinical tables list none established for hCG. One source fragment notes possible xanthine (caffeine, theophylline) interaction, but clinical significance is unclear.
• OHSS and thrombosis context: hCG triggers are a principal driver of OHSS; severe OHSS increases VTE risk. In high‑risk patients, use GnRH‑agonist trigger and freeze‑all; severe OHSS warrants thromboprophylaxis (often LMWH). This is a clinical co‑management issue rather than a PK interaction.

Mechanism‑based theoretical interactions

• Additive androgenic effects with exogenous androgens/anabolic steroids: hCG increases endogenous testosterone via LH‑receptor stimulation; combined use could heighten androgenic adverse effects (erythrocytosis, lipids/BP, BPH).
• Additive estrogenic milieu with estrogens or SERMs used in fertility care: hCG‑driven estradiol rise may compound VTE risk when combined with estrogen therapy/SERMs; ART with hCG triggers is associated with OHSS/VTE risk.
• Thyroid axis/test effects: hCG’s thyrotrophic activity can lower TSH and alter thyroid test interpretation; monitor and adjust thyroid replacement as needed.
• Laboratory assay interference: Exogenous hCG and altered sex steroids may confound interpretation of hormone assays, including hCG measurements (mechanism-based caution).
• Severe OHSS and PK alterations: Third‑spacing/hemoconcentration during severe OHSS may change the PK of renally cleared or narrow‑therapeutic‑index drugs; close monitoring and dose adjustment may be needed.
• Antagonism of androgen‑deprivation strategies in prostate cancer: hCG raises testosterone, opposing androgen‑suppression therapies; this underlies its contraindication in androgen‑dependent prostate cancer.

Clinical implications

• Before prescribing hCG, screen for pregnancy, hormone‑dependent tumors (especially prostate/breast), ovarian cysts/undiagnosed enlargement, precocious puberty, and uncontrolled thyroid/pituitary/hypothalamic disease.
• In ART, prefer non‑hCG triggers for high‑risk OHSS patients and employ thromboprophylaxis when severe OHSS occurs.
• Although established pharmacokinetic DDIs are not well documented for hCG, consider the above mechanism‑driven interactions and monitor accordingly.

Contraindications#

We reviewed clinical references and safety reviews to summarize human chorionic gonadotropin (hCG) contraindications, known interactions, and mechanism-based theoretical interactions.

Toxicology#

Scope and approach. We searched for toxicological endpoints for human chorionic gonadotropin (hCG) and recombinant hCG products across the retrieved corpus. Only one source in the corpus provided directly relevant information, and it focused on pharmacologic studies of hCG-derived oligopeptides rather than formal toxicology. Therefore, the answer reflects available evidence and explicitly indicates gaps.

• LD50 (acute lethality): Not identified in the retrieved sources. No acute median lethal dose data for hCG or recombinant hCG were found in the available corpus.

• Organ/system toxicity (animal studies): Not identified in the retrieved sources. We did not locate GLP toxicology studies with histopathology/clinical pathology endpoints for hCG in the retrieved materials.

• Mutagenicity/genotoxicity testing: Not identified in the retrieved sources. No Ames, micronucleus, or chromosome aberration data specific to hCG or recombinant hCG were present in the retrieved corpus.

• Dose–response relationships (contextual pharmacology, not toxicology): The available review summarizes efficacy dose-ranging in mice for hCG-derived oligopeptides. Examples include 5 mg/kg i.p. in LPS shock models; AQGV at 50 mg/kg twice daily for 4 days in a CLP sepsis model (limited therapeutic effect); LQGV with 5 mg/kg showing no significant tumor-volume reduction but improved response rate, and 17 mg/kg producing maximal tumor response; and 10 μg/day administered 3 times weekly for 3 weeks for LQGV/VLPALP in a diabetes model. These illustrate pharmacologic dose–response but do not constitute toxicology endpoints.

What is missing and implications

• The corpus did not yield product-label nonclinical toxicology sections (e.g., for urinary hCG products such as Pregnyl/Novarel or recombinant hCG such as choriogonadotropin alfa) that often state whether genotoxicity or carcinogenicity studies were conducted and their outcomes. Nor did it yield compendium entries (e.g., HSDB/RTECS) that might list acute toxicity values. As a result, we cannot report LD50 values, organ toxicity findings, or genotoxicity results based on the retrieved evidence.

• Given the biologic nature of hCG and its long-standing clinical use, labels often note that carcinogenicity studies have not been performed and genotoxicity testing is either negative or not conducted; however, these statements were not found in the retrieved sources and therefore cannot be cited here.

Conclusion. Within the retrieved evidence, no formal toxicological endpoints (LD50, organ toxicity, mutagenicity) for hCG were identified; only pharmacologic dose–response data for hCG-derived oligopeptides were available. Additional sources (regulatory labels, compendia) would be necessary to complete the toxicological profile.

Evidence Gaps#

• Human adverse event data is limited to anecdotal reports
• Systematic adverse event monitoring has not been conducted
• Drug interaction studies are incomplete
• Long-term safety profiles are unknown

Related Reading#

• HCG overview and research guide
• HCG dosing protocols
• HCG risks and legal status