hCG Protein

hCG is composed of two subunits: alpha (α) and beta (β). The alpha subunit is common to other glycoprotein hormones like luteinizing hormone (LH), follicle-stimulating hormone (FSH), and thyroid-stimulating hormone (TSH). The beta subunit, however, is unique to hCG and is responsible for its specific biological functions .

After conception, the fertilized egg (embryo) implants into the uterine wall, triggering the formation of the placenta. The placenta then begins to produce and release hCG into the bloodstream and urine . This hormone helps maintain the corpus luteum, which in turn secretes progesterone to thicken the uterine lining and support the growing embryo .

hCG levels rise rapidly in the early stages of pregnancy, peaking around the end of the first trimester before gradually declining . This hormone is also the basis for most pregnancy tests, as its presence in urine or blood indicates pregnancy .

Apart from its role in pregnancy, elevated hCG levels can also be indicative of certain types of cancer, such as trophoblastic disease and germ cell tumors . Therefore, hCG measurements are sometimes used in oncology to aid in diagnosis and monitoring treatment response.