Overview
Human chorionic gonadotropin (HCG) is a naturally occurring glycoprotein hormone produced primarily by cells in the placenta during pregnancy, though it is also found in smaller amounts in other tissues. It belongs to the gonadotropin family of hormones, which play a role in reproductive biology, and it shares structural similarities with other hormones such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH). HCG is perhaps best known as the hormone detected by pregnancy tests, but it has also drawn significant scientific interest in areas related to reproductive endocrinology, fertility research, and oncology — particularly in the study of gestational trophoblastic diseases such as choriocarcinoma, where beta-HCG levels are examined as a potential biomarker. Researchers also study HCG in the context of ovarian stimulation and hormonal signaling pathways. All information provided here relates strictly to research applications, and HCG as referenced in this context is intended for laboratory and scientific research purposes only, not for human use.
Research & Bioactivity
Researchers have studied human chorionic gonadotropin (hCG) extensively in the context of reproductive biology, endocrinology, and oncology. In reproductive research, studies have examined its role in signaling pathways related to ovarian stimulation, luteal support, and early pregnancy physiology, including investigations into how intracellular signaling mechanisms may influence outcomes in models of poor ovarian response. Research has also investigated hCG as a biomarker in gestational trophoblastic disease, including choriocarcinoma, where the beta subunit (β-hCG) has been studied in relation to diagnosis, disease monitoring, and the detection of residual or recurrent disease in clinical settings. Additional studies have explored the behavior of β-hCG levels in atypical presentations of ectopic pregnancy, including cases where standard serum and urine measurements produced unexpected results, contributing to a broader understanding of its reliability as a diagnostic marker. Beyond reproductive contexts, research has examined hCG's involvement in androgen biosynthesis pathways, with some studies using hCG stimulation protocols to investigate conditions such as 5α-reductase type 2 deficiency in animal and clinical research models.
Published Research
Laparoscopy-confirmed complete tubal abortion of an ectopic pregnancy with undetectable urine and serum beta-hCG levels.
Collis K, Ashfaq S, Cirelli C, Sheth H — 2026
We present a case of a woman in her 20s with right iliac fossa pain. Initial investigations showed mildly elevated inflammatory markers and serum beta human chorionic gonadotrophin (hCG) <1 mIU/mL. She was taken to theatres as a presumed early appendicitis but found to have haemoperitoneum with a free-floating cystic structure in the pouch of Douglas with intact pelvic organs. This was subsequently confirmed histologically as a gestational sac which had likely been expelled via the abdominal ostia into the peritoneal cavity (a so-called complete tubal abortion). She made a good postoperative recovery and was discharged with no complications. This case highlights the rare but important potential for ectopic pregnancy and its complications to be present despite a negative serum beta-hCG.
Can a focus on intracellular signaling assist us with ovarian stimulation in poor-prognosis patients?
Toner JP, Pirtea P, de Zieger D — 2026
Poor ovarian response remains one of the most challenging phenotypes in reproductive medicine. Research suggests that diminished ovarian reserve (DOR), advanced maternal age (AMA), and unexpected poor response (POR) may be due to different pathophysiologies, requiring distinct clinical management. This review focuses on the biological mechanisms that may provide an avenue for improved clinical outcomes by enhancing oocyte quality through more targeted therapy: 1. differing FSH isoforms, 2. FSH dose effects, 3. distinct signaling pathways of LH and hCG, 4. androgen priming, 5. growth hormone, 6. letrozole co-treatment, 7. coenzyme Q10, 8. Platelet-rich plasma and 9. mTOR inhibitors. Basic and clinical evidence is presented, and the therapeutic implications for treatment of the primary defect are explained. Although the clinical evidence is not yet strong for many of these factors, all are biologically plausible. This constitutes a "call to action" to correctly evaluate their possible role in improving ART outcomes.
Biomarker Revolution in Choriocarcinoma: Beyond β-hCG - Emerging Tools for Diagnosis, Prognosis & Therapeutic Monitoring.
Mangla M, Palo S, Setty A, Kaur H — 2026
Choriocarcinoma, a rare yet highly aggressive gestational trophoblastic neoplasia, is uniquely responsive to chemotherapy. The serum marker β-human chorionic gonadotropin (βhCG) has long been central to its diagnosis and monitoring, but not without limitations. Persistent false positives, poor specificity for residual disease or resistance, and slow detection of relapse are a few to mention. Advances in precision oncology have introduced novel biomarkers, such as ctDNA, circulating tumor cells (CTCs), exosomes, miRNAs, and exosomal miRNAs, that promise improved specificity, early relapse detection, and personalized monitoring. This review encapsulates the current landscape of emerging biomarkers in choriocarcinoma, categorizes them by methodological class and clinical utility, discusses integration challenges, and outlines future research directions toward multi-marker precision diagnostics.
Rupture of interstitial ectopic pregnancy secondary to invasive hydatidiform mole with pelvic metastasis in perimenopausal women: A case report.
Xu L, Li Y, Wang T, Zhao Y — 2026
RATIONALE: Ectopic gestational trophoblastic disease is an extremely rare subtype of gestational trophoblastic disease, with perimenopausal cases especially scarce and prone to preoperative misdiagnosis as a common ectopic pregnancy, leading to potential delays in proper management. PATIENT CONCERNS: A 50-year-old perimenopausal woman (G6P2) presented with acute abdominal pain, dizziness, profuse sweating, and hemorrhagic shock. She had a 4-month amenorrhea, a history of ectopic pregnancy surgery, and uterine curettage. Preoperative assessment suggested ectopic pregnancy rupture with massive intra-abdominal hemorrhage, without initial suspicion of trophoblastic neoplasia. DIAGNOSES: Emergency laparoscopic surgery and pathological examination confirmed interstitial ectopic pregnancy rupture secondary to invasive hydatidiform mole with pelvic soft tissue invasion. International Federation of Gynecology and Obstetrics stage II, World Health Organization prognostic score 10 (intermediate-high risk). INTERVENTIONS: Emergency laparoscopic wedge resection of the left uterine horn lesion, uterine reconstruction, and bilateral uterine artery ligation were performed. Postoperative standardized etoposide, methotrexate, actinomycin-D, cyclophosphamide, vincristine chemotherapy was administered, followed by 3 cycles of consolidation chemotherapy after beta-human chorionic gonadotropin (β-hCG) normalization. OUTCOMES: Serum β-hCG returned to normal at 8 weeks postoperatively. No severe chemotherapy adverse reactions occurred. No recurrence was detected during regular follow-up. LESSONS: Perimenopausal women with amenorrhea, acute abdominal pain, and extremely elevated β-hCG (>105 IU/L) should raise a strong suspicion of ectopic gestational trophoblastic disease. Integrated clinical, imaging, laboratory, and pathological evaluation reduces misdiagnosis. Surgical lesion resection combined with standardized etoposide, methotrexate, actinomycin-D, cyclophosphamide, vincristine chemotherapy, and close follow-up yields a favorable prognosis.
Clinical characterization and analysis of the SRD5A2 gene in 16 Chinese patients with 5α-reductase type 2 deficiency: a single-center retrospective study.
Shen L, Fu D, Yang W, Cui Y, Wang H, et al. — 2026
BACKGROUND: 5α-reductase type 2 deficiency(5α-RD2) is a rare autosomal recessive disorder primarily caused by variants in the SRD5A2 gene. This condition is characterized by a spectrum of undervirilization in 46, XY individuals, ranging from ambiguous genitalia to predominantly male external genitalia with minimal undervirilization. Early diagnosis and effective management of 5α-reductase type 2 deficiency patients are major challenges for healthcare providers. The mutational analysis of SRD5A2 gene is regarded as the gold standard for the diagnosis of the disease. This study aimed to summarize our center's experience with patients diagnosed with 5α-reductase type 2 deficiency due to variations in the SRD5A2 gene and the associated clinical manifestations to enhance clinicians' awareness of this condition. METHODS: We conducted a retrospective single-center study by reviewing the medical records of patients diagnosed with 5α-reductase type 2 deficiency after genetic testing between April 2018 and July 2025. RESULTS: All 16 patients presented with ambiguous genitalia at birth and received diagnoses between the ages of 3 months and 11 years and 3 months. Of these patients, ten exhibited micropenis accompanied by hypospadias, six displayed an isolated micropenis, and six had either bilateral or unilateral cryptorchidism. Additionally, six patients had an underdeveloped scrotum. All affected individuals had a 46, XY karyotype and tested positive for the SRY gene, with two patients initially raised as female. The testosterone/dihydrotestosterone (T/DHT) ratios after human chorionic gonadotropin (hCG) stimulation ranged from 1.5- to 38.6-fold above the baseline values. This study identified ten distinct pathogenic variants of the SRD5A2 gene, including nine previously reported variants p.Gln6Ter, p.Gly66Arg, p.(Tyr128Cys), p.Asn193Ser, p.Gly196Ser, p.Gly203Ser, p.Phe219Serfs*60, p.Arg227Gln, and p.Arg246Gln and one novel variant p.(Cys119Arg), which expands the spectrum of known SRD5A2 variants. CONCLUSION: This study provides insights into genotype-phenotype correlations in a cohort of 16 Chinese patients diagnosed with 5α-reductase type 2 deficiency and summarized the enzymatic activity of the identified genetic variants. Identifying variants associated with 5α-reductase type 2 deficiency will facilitate genetic counseling for at-risk families and enable prenatal diagnosis, thus empowering parents to make informed decisions and allowing healthcare providers to tailor treatment strategies effectively.