The difference between Pregnyl (urine derived hCG) and Ovidrel (recombinant hCG)
Being less glycosylated, Ovidrel has a shorter half-life, which reduces the likelihood of hyper-stimulation.
Ms. Ortega is here to discuss freezing eggs. This will be her second attempt – she had 5 mature eggs (M II) from a prior attempt elsewhere. She reports a lot of bloating after the retrieval and the bloating resolved spontaneously 10 days later. She asked if something could be changed.
Her stimulation can be summarized as the following: the peak estradiol was 1700s pg/mL, there were nine antral follicles on the day of the baseline, Gonal F 300 units daily was used for 10 days, Antagon was started when the lead follicle was 14 mm, Ovidrel 250 mcg was used for trigger.
Based on the onset and the duration of the symptom, the bloating is most likely due to enlarged ovary. The ovary became enlarged after the retrieval because there was a “second wave” follicle growth, which was caused by Ovidrel, which is a recombinant hCG.
The trigger shot in ART (assisted reproductive technology) replaces the natural LH surge before ovulation (the physiological roles of LH surge will be discussed in a separate post). Although LH can be (and is) used for trigger in ART, hCG (either Pregnyl or Ovidrel) is more commonly used, because (1) LH receptor can be activated by hCG, (2) hCG is more readily available (and therefore, cheaper), and (3) relative to LH, hCG stays longer in the body.
Both Pregnyl and Ovidrel are hCG. Pregnyl, a natural hCG, is extracted from pregnant women’s urine. Ovidrel, a recombinant hCG, is produced by cultured Chinese Hamster ovary cells carrying human hCG gene.
The less commonly used LH trigger is achieved via Lupron injection. Lupron is a GnRH (gonadotropin releasing hormone) agonist, which makes the pituitary gland release LH (and FSH).
Pregnyl and Ovidrel are identical in terms of amino acids. But they contain different numbers of sugar molecules, i.e., they have different degrees of glycosylation. Glycosylation is a natural process where sugar molecules are added to newly synthesized peptide, such as hCG. Glycosylation affects many characteristics of peptide, including how fast it is degraded or eliminated. All other things being equal, more glycosylation means slower degradation and elimination.
The elimination half-life of Pregnyl, Ovidrel, and LH are 29 ± 6 hours, 48 hours, and 20 minutes, respectively. Normally, it takes 5.5 half-lives to clear a compound completely. So, it takes 264 hours (11 days), 160 hours (6.6 days), and 110 minutes to eliminate Pregnyl, Ovidrel, and LH, respectively from the body.
Among the three agents for trigger, Lupron is the best choice. Lupron releases LH, which is eliminated after 110 minutes. The “second wave” follicle growth is kept to the minimum.