Tumour marker
Human chorionic gonadotropin serves diagnostically as a tumor marker, since some malignant tumors, especially tumors of the gonads (testicles and ovaries) and placenta, produce the hormone. In rare cases this also applies to tumours of other tissues such as the mammary gland, liver, lungs or intestines. However, like most tumour markers, HCG is not used to diagnose the presence of a malignant disease, but rather as a follow-up or prognostic parameter for already diagnosed tumours. In metastasized germ cell tumors of the testis, for example, the concentration of hCG is considered to be a characteristic that determines the prognosis in good, intermediate or poor. Higher serum levels are associated with a worse prognosis.
Pregnancy test
Almost all pregnancy tests measure the concentration of hCG in urine or blood. One week after fertilisation, there may already be a sufficient level in the blood to be able to determine the pregnancy by means of a laboratory test – i.e. even before the menstruation stops. After 2 weeks at the earliest, the concentration in the urine is also so high that the hormone can be detected with the aid of the freely available pregnancy test.
The test works with the help of colour-marked antibodies which bind specifically to hCG. A positive test usually has two pink stripes, while a negative test shows only one. At this point in time, however, the significance of a negative test result is limited – it can also take 5 to 6 weeks before the hormone is detectable in the urine.
The concentration of hCG is highest in morning urine, so the best time for a pregnancy test is in the morning. A false positive result (i.e. a positive test in the absence of pregnancy) can, for example, be caused by an hCG-producing germ cell tumour. For this reason, a blood sample should always be taken and an ultrasound examination performed after the test.
