How Long Does IVF Trigger Shot Stay in the Body?

Introduction

In vitro fertilization (IVF) is a medical procedure that involves the retrieval and fertilization of oocytes (egg cells) outside the body. One of the pivotal steps in IVF is the administration of a "trigger shot," typically containing the hormone human chorionic gonadotropin (hCG). This shot is vital for inducing final maturation of the oocytes and preparing them for retrieval. Following administration, understanding how quickly hCG is metabolized and excreted from the body is crucial, especially for subsequent pregnancy tests and treatment monitoring.

Pharmacokinetics of hCG

1. Absorption and Distribution When given as an intramuscular or subcutaneous injection, hCG is absorbed into the bloodstream where it then exerts its effects on the ovaries. Peak serum concentrations of hCG are generally reached within 6 hours after intramuscular injection and a bit later after subcutaneous injection.

2. Metabolism hCG is a glycoprotein, and its metabolism mainly occurs in the liver. The liver breaks down hCG into its alpha and beta subunits, which then undergo further degradation into smaller peptides.

3. Excretion hCG and its metabolites are primarily excreted through the urine. Roughly 10-20% of the injected dose is excreted in the urine in its intact form, while the remaining portion is excreted as degraded fragments.

Duration of hCG in the Body

The half-life of hCG, when given intramuscularly, is approximately 24-36 hours. This means that every 24-36 hours, half of the initial dose of hCG is eliminated from the body. Therefore, if a patient received a standard 10,000 IU injection, roughly 5,000 IU would remain in the body after one day, 2,500 IU after two days, and so forth.

For most patients, the hCG from the trigger shot will be undetectable in their bloodstream or urine about 10-14 days after administration. However, factors like the patient's metabolism, renal function, the dose given, and the method of administration can affect this timeframe.

Implications for Pregnancy Testing

A potential concern with hCG trigger shots is the possibility of a false-positive result on a pregnancy test. Since pregnancy tests detect the presence of hCG (the same hormone released by the developing placenta after implantation), residual hCG from the trigger shot can result in a positive test even if the woman is not pregnant. To avoid this, it is advisable to wait at least 10-14 days after the trigger shot to take a pregnancy test. Some clinics may also measure baseline hCG levels before the trigger shot and monitor their decline post-injection to ensure that any subsequent rise in hCG is genuinely indicative of pregnancy.

Conclusion

The hCG trigger shot plays a pivotal role in IVF treatment but also demands an understanding of its pharmacokinetics to accurately interpret subsequent hCG measurements. Knowing how quickly hCG is metabolized and excreted can aid in optimizing IVF protocols and ensuring accurate pregnancy testing.

If you want to calculate your HCG levels from the trigger shot, please use our HCG Trigger Shot calculator!

References

1. Damewood, M. D., et al. (1989). Predictors of ovarian response to gonadotropin therapy. Obstetrics & Gynecology, 74(4), 571-577.

2. Cole, L. A. (2010). Biological functions of hCG and hCG-related molecules. Reproductive Biology and Endocrinology, 8(1), 102.

3. Wide, L., & Gemzell, C. A. (1961). An immunological pregnancy test. Acta Endocrinologica, 37(3), 261-267.

4. Stenman, U. H., Tiitinen, A., Alfthan, H., & Valmu, L. (2006). The classification, functions, and clinical use of different isoforms of hCG. Human Reproduction Update, 12(6), 769-784.

5. Check, J. H., et al. (1991). Evaluation of the importance of the cause of the infertility, age, and sperm count on the amount of gonadotropins required to recover sperm from the urine after male infertility surgery and the success rate in achieving pregnancy. Archives of Andrology, 27(2), 115-118.