What HCG Actually Is: The Hormone, the Pregnancy Test and the Diet That Borrowed Its Name

Human chorionic gonadotropin (HCG) is a hormone associated with pregnancy, the hormone that pregnancy tests are built around, and the name that a mid-20th-century diet claim appropriated - while making a separate weight-loss promise.

The HCG Hormone

HCG is a hormone and a placental polypeptide, according to PubChem. This means it is a relatively small protein made in the placenta, the new organ that grows from a fertilized egg and attaches to the wall of the uterus to nourish and protect a growing embryo and fetus.

The main medical use for HCG is as a way of detecting early pregnancy. Home HCG tests are cleared by the FDA as qualitative screens to see whether elevated HCG levels are present in urine, which would likely indicate that a woman is pregnant.

The FDA guidelines describe the tests as meant to measure any of several slightly different HCG molecules in urine. That would include intact HCG, slightly modified HCG, and any free HCG subunits.

Physiologically, the hormone appears in blood and urine early in pregnancy and rises as it progresses.

So for an accurate HCG test, the timing matters. The defining factor is how much HCG shows up: median HCG levels in early pregnancy can climb from 5 mIU/mL to 5200 mIU/mL over a 30-day period.

During mid-pregnancy the rise is slower, and from weeks 12 to 21, HCG may actually drop slightly before rising again. Any sudden drop in first-trimester HCG can be a sign of a problem.

How Pregnancy Tests Use the Hormone

In a set of guidelines, the FDA cleared HCG tests as an early pregnancy screen, for use based on finding enough HCG in urine.

The guidance establishes risk classifications for HCG pregnancy tests. Most home kits are in the low-risk category, lists the FDA. Low-risk tests mean no systemic blood contact, no needed controls, and a intended qualitative readout.

HCG test systems are classed as 510(k) medical devices, which can be approved through a simplified, cheaper path than full clinical trials.

An example regulator view of an HCG test sold as a “1-step” home pregnancy test shows a decision record from July 10, 1996. This cleared the device for detecting HCG in urine - but notes that HCG tests can have other intended uses.

HCG is used in tumor detection and in fertility treatment, medical references state, because the hormone is made not only in pregnancy but also by some tumors.

HCG is also sometimes given in outpatient procedures for men with low sperm counts.

FDA-Approved Uses

Pregnancy is not the only use for tests of HCG in urine. HCG in urine may be tested not just for early pregnancy screens but for multiple other tumor-related diagnoses, and even infertile men with low sperm counts, according to FDA regulations.

The FDA cleared the home (“over-the-counter”) version of HCG Pregnancy Tests and categorized them as qualitative urine and blood tests.

HCG Tests are unlikely to be used to diagnose a birth defect or disorder or birth date. The tests are made to provide qualitative or quantitative readings of HCG in blood or urine and are regulated.

The FDA guidance says pregnancy HCG tests have a minimum threshold to confirm pregnancy.

The Origins of The 'HCG Diet'

A separate claim entitled "The HCG Weight Loss Plan", published in 1961, claimed that very low calorie diets, combined with HCG injections, could cause real weight loss and preferentially target adipose tissue.

The HCG Diet was promoted by A. T. W. Simeons, a British physician working in India in the 1950s. He studied patients diagnosed with underactive gonads. The HCG injections, originally meant to aid gonad growth, caused these patients to lose 25 percent of body weight, Simeons published in a 1954 paper.

After Simeons, the HCG Diet hit the popular media and became a book, but no data was published proving its general utility. Over the decades, studies failed to replicate these findings.

Medical Uses Versus The Diet's Claims

Separating the medical from the diet is essential. HCG, the marker used to detect pregnancy, is biologically unique. It is produced only in a few clinical scenarios, mostly in pregnancy and some gonad cancers. It's never, in the animal or human physiology already fully characterized in endocrinology, an agent of fat removal.

When a human is pregnant, several certain organs make HCG, and specific sites in the trophoblast, syncytiotrophoblasts, and cytotrophoblasts. Content in samples correlate to trophoblast growth and differing trimesters. Physiologically, HCG is another way of comparing the current time point in gestational development to a prior gestational consideration.

Medically speaking, if a new pregnancy test shows the hormone, something either rare or predictable is going on. If it doesn't, the outcome is normal, and otherwise interpretive. But regardless of other contexts, weight loss, if any from pregnancies' HCG, is never intentional or output-tailorable, and the diet's idea contradicts the traits of the hormone.

The FDA cleared qualitative urine tests that measure cut points not shared with the HCG Diet, and never to be used for gaining weight.

The HCG diet is a different thing entirely. If the hormone actually caused weight loss, there's no data of it used with the uncontrolled randomized trials expected of FDA dosage forms, and nor promoted via the creative prescription delivery options needed. So it can't be separated from obesity gain/prescription, but the FDA battery of tests cannot fail to interpret accidental pregnancy with HCG-Diet-met criteria, and never should.