HCG dosage protocol

What the compound is

Human chorionic gonadotropin (hCG) is a heterodimeric glycoprotein composed of two subunits (PMID 29772831). It is recognized for its roles in ovulation and supporting early pregnancy (PMID 24365330). Classical hCG is the first molecule synthesized by the embryo, with its RNA transcribed as early as the eight-cell stage, and the protein is produced by the blastocyst before implantation (PMID 35163303). hCG has four major isoforms: classical hCG, hyperglycosylated hCG, free β subunit, and sulphated hCG (PMID 35163303). The main form of hCG in circulation and in patients with trophoblastic tumors is intact heterodimeric hCG (PMID 24275190).

hCG and luteinizing hormone (LH) share similar molecular structures and a common receptor, but emerging evidence suggests they have distinct effects on downstream signaling (PMID 24365330). hCG is detectable in maternal circulation shortly after the embryo starts secreting it and its concentration increases throughout early pregnancy as the placenta forms (PMID 31921157).

How it is thought to work

hCG and its receptor, LH/CGR, are expressed in various sites of the reproductive tract, including both gonadal and extra-gonadal tissues, where they promote oocyte maturation, fertilization, implantation, and early embryo development (PMID 28505106).

hCG serves as one of the first signals provided by the embryo to the mother, initiating the implantation process (PMID 31921157). It not only regulates biological aspects of these early pregnancy events but also supports maternal immune cells in their function to establish an adequate embryo-endometrial relationship (PMID 31921157). hCG has the potential to influence both local uterine immune cell populations and peripheral immune cells (PMID 31921157).

Placental heterodimeric hCG acts as a protective agent against breast cancer by imprinting a genomic signature on the mammary gland that makes it resistant to malignant transformation, characterized by cellular differentiation, programmed cell death (apoptosis), and growth inhibition (PMID 28754015).

What laboratory and animal studies report

No specific laboratory or animal studies were detailed in the provided abstracts, which primarily focused on human physiological roles and general mechanisms.

Human evidence so far

In humans, determination of hCG is used for diagnosing and monitoring pregnancy, pregnancy-related disorders, and certain tumors (PMID 24275190). The free β subunit (hCGβ) may be the major form in aggressive trophoblastic cancer (human finding, PMID 24275190). Assays that measure both hCG and hCGβ are mainly used for diagnosing pregnancy and trophoblastic diseases (human finding, PMID 24275190). Specific determination of hCGβ is valuable in screening for Down's syndrome and diagnosing non-trophoblastic cancer (human finding, PMID 24275190).

Pregnancy is a protective factor against breast cancer, and hCG is a candidate hormone mediating this anti-tumor effect (human observation, PMID 28754015). Mimicking pregnancy by treatment with hCG is suggested as a strategy for breast cancer prevention (human context, PMID 28754015). Conversely, ectopic expression of β-hCG in various cancer entities in humans is associated with poor prognosis due to its tumor-promoting function (human observation, PMID 28754015).

Open questions and limitations

Future research needs to extensively focus on the functions of hCG and its receptor LH/CGR to reveal known and unknown clinical potentials (PMID 28505106). Increased understanding of the inherent differences between LH and hCG will foster more effective diagnostic and prognostic assays for various clinical contexts and support individualized treatment strategies for conditions like infertility (PMID 24365330). The role of hCG in breast cancer appears to be a paradox, with placental hCG acting protectively while ectopically expressed β-hCG is associated with poor prognosis (PMID 28754015).

The assay of hCG is complicated by the occurrence of different molecular forms, which are detected to varying degrees by different assays (PMID 24275190). When excreted into urine, most hCG (and hCGβ) breaks down to the core fragment of hCGβ (hCGβcf), which is the main immunoreactive form of hCG in urine during pregnancy (PMID 24275190). hCGβcf has limited utility but is important because it may interfere with hCG assays in pregnancy (PMID 24275190).

Key terms explained

A 'heterodimeric glycoprotein' is a protein that consists of two different subunits joined together, and it has carbohydrate (sugar) chains attached (PMID 29772831). 'Oocyte maturation' refers to the process where an immature egg cell develops and prepares for fertilization (PMID 28505106). 'Implantation' is the attachment of the embryo to the wall of the uterus (PMID 28505106). 'Apoptosis' is a process of programmed cell death (PMID 28754015). 'Ectopic expression' means that a gene is expressed in a cell type or tissue where it is not normally expressed (PMID 28754015). 'Trophoblastic tumors' are a group of rare tumors that grow in a woman's uterus after conception (PMID 24275190).