Pregnyl
Meaning of Pregnyl: The trigger shot of fertility treatment: an injected pregnancy hormone borrowed because it fits the receptor that normally releases an egg.
Definition of Pregnyl
Pregnyl is a brand of human chorionic gonadotropin for injection, a hormone purified from the urine of pregnant women. It attaches to the same receptor as luteinizing hormone, the pituitary signal that releases a mature egg. It is given to bring on ovulation during fertility treatment and to stimulate testosterone and sperm production in men whose own pituitary signal is missing.
What is in the injection?
Human chorionic gonadotropin, the hormone a developing placenta pours out in early pregnancy. The hormone in this product is collected and purified from the urine of pregnant women, which remains the cheapest source of it. That is worth stating plainly, because drug lists often file the brand under the recombinant version of the hormone. A recombinant form does exist, grown in cultured cells rather than harvested, but it is a separate product sold under a different generic name.
Why does a pregnancy hormone bring on ovulation?
Because it fits the wrong lock, usefully. Luteinizing hormone from the pituitary gland is the natural signal that completes egg maturation and releases it, and chorionic gonadotropin is close enough in shape to occupy the same receptor. It also survives much longer in the bloodstream, so a single injection delivers a sustained push where the natural signal arrives as a brief surge. That predictability is the whole point in fertility treatment, since egg collection has to be scheduled. An alternative trigger works instead through gonadotropin-releasing hormone, acting one step earlier in the chain.
What else is it used for?
| Setting | What the hormone does there |
|---|---|
| Fertility treatment in women | Completes egg maturation and triggers release |
| Absent pituitary signal in men | Drives the testes to make testosterone and sperm |
| Undescended testicle in boys | Sometimes used to prompt descent |
| Marketed weight loss programs | No effect; any loss comes from the severe diet attached |
The last row is the one that has drawn repeated warnings from regulators, since the hormone has never been shown to reduce weight, hunger or fat distribution. Within fertility use the sustained stimulation carries a risk of its own: ovaries already primed by earlier drugs can swell and leak fluid into the abdomen, a reaction called ovarian hyperstimulation syndrome.
Also known as
Used in a sentence
Pregnyl was administered as an ovulation trigger following controlled ovarian stimulation.
Good to know
The hormone in this product is purified from urine rather than made by recombinant methods, and because pregnancy tests detect the same hormone, an injection can produce a positive result for days afterward in someone who is not pregnant.