Beta human chorionic gonadotrophin (beta HCG or HCG) is secreted by the placenta. The blood level rises to a peak at 10 weeks of pregnancy, and then slowly declines. Its presence can be used as a diagnostic test for pregnancy, but can only be detected at least ten days after conception. Its presence also acts as a reliable marker for certain cancers of the ovary and testes. The interpretation of blood levels are as follows:-
- Less than 10 IU/L. – normal non-pregnant.
- 20 to 100 IU/L – 1 to 2 weeks after pregnancy commences, or menopause
- 100 to 6000 IU/L – 3 to 4 weeks of pregnancy, or after 6 months of pregnancy, or cancers of ovary or testicle (embryonal carcinoma or choriocarcinoma).
- 6000 to 30,000 IU/L – increases between weeks 7 and 30 of pregnancy, and then slowly decreases.
- Over 30,000 IU/L – increased risk of Down syndrome (mongolism).
Most HCG tests for pregnancy are performed on urine. The tests indicate whether the HCG is over a threshold level of HCG and merely indicate a positive or negative result. False positive results can occur with cancers of ovary or testes (seminomas, choriocarcinoma) or placental tumour (hydatidiform mole). False negatives are far more common and can occur with very dilute urine, if the pregnancy has not progressed far enough to produce sufficient HCG or with kidney diseases. The peak level of urine HCG is reached at 10 weeks pregnancy, after which it declines, so a urine pregnancy test after about 20 weeks of pregnancy may be negative.
Chorionic gonadotrophin can also be injected as a medication in the treatment of infertility in women, delayed puberty in girls, failure of testicular development and failure of sperm production. It may result in multiple pregnancies and may cause fluid retention. It must not be used by patients suffering from some types of cancer affecting the sex organs.
Although chorionic gonadotropin has been prescribed to help some patients lose weight, it should never be used this way. When used improperly, chorionic gonadotropin can cause serious problems.