hCG

Where it comes from

Made in

Trophoblast cells of the embryo from about a week after fertilisation; the placenta thereafter

Sent out by

Doubles every two days in early pregnancy, peaks at ten weeks, then falls

Acts on

• Corpus luteum (progesterone)
• Fetal testis (testosterone)
• Uterine lining and spiral arteries
• Thyroid, weakly (it resembles TSH)

What it does

• Keeps the corpus luteum making progesterone until the placenta can
• Drives the fetal testis to make testosterone
• Its thyroid-like effect raises thyroid hormone in early pregnancy, and hyperemesis goes with the highest levels

In medicine

• The pregnancy test, in urine and blood, and the marker that tracks ectopic pregnancy, miscarriage and molar pregnancy
• A tumour marker for choriocarcinoma and germ cell tumours
• Urinary chorionic gonadotropin is approved to induce ovulation in anovulatory infertility, for prepubertal undescended testes, and for selected men whose hypogonadism comes from the pituitary ²; choriogonadotropin alfa, the recombinant form, is approved to mature the follicle in assisted reproduction and to induce ovulation

Beyond the body’s own use

• The hCG diet pairs the hormone with about 500 calories a day. A meta-analysis traced 24 trials, found the better-conducted ones were the controlled ones, and of those only one reported any benefit: no weight lost beyond the calorie restriction, no change in where fat sits, no less hunger ¹
• The regulator says the same twice over. The approved label states there is no substantial evidence it adds anything to calorie restriction, and the agency advises against the drops, pellets and sprays, which are approved for nothing and are not reviewed for safety, effectiveness or quality ²³
• Men taking anabolic steroids use it to keep the testes working. In sport it is prohibited in males at all times, as a testosterone-stimulating peptide ⁴