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HCG

HCG or human chorionic gonadotropin is the same hormone produced by the pregnancy that is measured to determine if someone is pregnant. It is structurally very similar to the important reproductive hormone LH and is commonly used in its place. (It has a longer half-life than LH.) Most HCG is purified from urine from pregnant women. Recently, HCG has been produced by strict laboratory methods (recombinant HCG) as the drug Ovidrel. LH is also available as a recombinant product.

HCG used to be used solely to trigger ovulation, but we are finding more and more reasons to use it for fine tuning the ovulation process and enhancing implantation. I prefer to use Ovidrel to trigger ovulation since this is such a key step in the management and control of a fertility cycle. Rarely, urinary HCG has not performed well (see the literature of the "Empty Follicle Syndrome"). It is also harder to use urinary HCG to trigger ovulation than Ovidrel and therefore Ovidrel is less likely to cause patient administration errors.

I generally prefer urinary HCG to recombinant LH because it is very much cheaper and has a longer half-life. We mix and administer HCG is several different ways depending on the planned application. In some IVF cycles we will use it three different ways in the same cycle!

HCG works very differently, depending on when it is taken. After ovulation, it enhances implantation. This is well demonstrated in the medical and basic science literature. However, its use is limited, because it may cause ovarian hyperstimulation if given to some patients at this time. In contrast, recent data suggests that HCG can be used earlier in the cycle to prevent ovarian hyperstimulation. Similarly, if given in a high enough dose at an appropriate time, HCG may initiate oocyte maturation with production of the first polar body and the follicle wall break down necessary to release a fertilizable egg into the abdomen. However, if given at the same dose earlier in the cycle, it may render all of the eggs incapable of becoming pregnancies!

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