Human Chorionic
Gonadotropin

1890s-1927

The Pregnancy Puzzle

Searching for Chemical Proof of Life

For centuries, determining pregnancy was unreliable. Women relied on missed periods and physical symptoms, but certainty came only when the baby moved. Doctors needed something better.

In the early 20th century, scientists discovered hormones — chemical messengers that controlled body functions. They suspected pregnancy might produce unique hormones that could be detected. The race was on to find them.

In Berlin, Selmar Aschheim and Bernhard Zondek began experimenting with urine from pregnant women. When injected into immature female mice, something remarkable happened: the mice's ovaries developed and ovulated as if they were adult animals.

1927-1950

The A-Z Test

The First Reliable Pregnancy Test

In 1927, Aschheim and Zondek published their breakthrough: the A-Z test. Inject a woman's urine into mice; if she's pregnant, the hormone in her urine will cause the mice to ovulate within days. It was the first reliable early pregnancy test.

The hormone was named Human Chorionic Gonadotropin — 'chorionic' because it came from the chorion (part of the placenta), 'gonadotropin' because it stimulated the gonads. HCG appeared in urine just days after a missed period.

The A-Z test spread worldwide. By the 1940s, rabbits replaced mice (the 'rabbit test'). For the first time, pregnancy could be confirmed within weeks rather than months.

1950-1980

From Diagnosis to Treatment

HCG Enters Fertility Medicine

Scientists discovered that HCG could do more than detect pregnancy — it could help create it. The hormone mimicked LH (luteinizing hormone), the signal that triggers ovulation. Injecting HCG at the right moment could force ovulation in women who struggled to conceive.

For men, HCG offered something different. By mimicking LH, it could stimulate the testes to produce testosterone. This was useful for boys with undescended testicles and men with certain types of infertility.

HCG was purified from pregnant women's urine and became a standard fertility drug. Pharmaceutical companies developed injectable preparations. What had been a pregnancy marker became a pregnancy enabler.

1980-2010

The IVF Era

Critical to Reproductive Technology

The development of in vitro fertilization (IVF) made HCG even more important. In IVF, doctors need to precisely control when eggs are released. HCG injection triggers ovulation about 36 hours later, allowing perfect timing for egg retrieval.

Recombinant HCG — made in labs rather than purified from urine — provided more consistent preparations. Pregnancy tests evolved from live animals to immunological tests, then to home test strips. The same hormone that enabled diagnosis now enabled treatment.

Meanwhile, athletes discovered that HCG could restart testosterone production after steroid use. This led to its addition to banned substance lists, creating a tension between legitimate medical use and performance enhancement.

2010-Present

Hormone Restoration

New Applications for an Old Hormone

Today, HCG has found new roles. Men on testosterone replacement therapy use it to maintain testicular function and fertility. It prevents the testicular shrinkage that can occur when external testosterone shuts down natural production.

The hormone is also used in weight loss protocols, though this application remains controversial. Some clinics combine HCG with very low-calorie diets, claiming it helps preserve muscle and reduce hunger. The FDA has not approved this use.

From pregnancy announcement to fertility enabler to hormone optimizer, HCG's journey reflects our growing understanding of the endocrine system. A hormone discovered through mouse experiments nearly a century ago remains central to reproductive medicine.