Highly purified Metrodin, with no residual luteinising hormone, thus equivalent in activity to recombinant FSH. Called Metrodin HP outside the US. Made by Serono.

A GnRH-analog that (unlike GnRH-agonists) immediately stops the pituitary gland from releasing the gonadotropins follicle stimulating hormone (FSH) and luteinising hormone (LH). Can substitute for GnRH-agonists for many gynecological purposes (particularly to suppress the LH-surge in assisted conception), although its use with pure FSH preparations (such as Fertinex, Gonal-F, Metrodin HP or Puregon) can lead to poor egg quality unless the dosage is carefully controlled or some luteinising hormone is added to the stimulation regimen.

Human menopausal gonadotropin (hMG) from which luteinising hormone (LH) has largely been removed, leaving follicle stimulating hormone (FSH) as the active substance. Metrodin HP (Fertinex in the US) is more purified, other urinary proteins having been extracted too, and (unlike Metrodin) has no LH activity at all. Made by Serono.

Called Fertinex in the US. Metrodin that has been highly purified by removing all contaminating urinary proteins and all luteinising hormone, and is thus similar in action to recombinant follicle stimulating hormone.

(rFSH) Follicle stimulating hormone derived from genetic engineering instead of being extracted from the urine of postmenopausal women (human menopausal gonadotropin, or hMG) or from the pituitary glands of cadavers (human pituitary gonadotropin, or hPG). Produced and marketed by the two pharmaceutical companies Organon (as Puregon), or Fertinex in the US and Serono (as Gonal-F) to replace their hMG preparations. Has the advantage over hMG (and its purified derivatives) of being standard in biological structure and activity, and of not being of a human source (hPG -- but not hMG -- having been implicated in transmission of Creutzfeldt-Jakob disease).

A variation of the short protocol for using GnRH-agonists with injections of follicle stimulating hormone (FSH) for controlled induction of superovulation in assisted conception programs. The GnRH-agonist is started with menstruation, a day or two before the injections of FSH start, and is discontinued after about 5 days from starting it (i.e. often a week or more before ovulation). There are no special advantages, whereas there's a potential disadvantage: a much more thorough suppression of the woman's own luteinising hormone (and maybe FSH) than if the GnRH-agonist is continued -- potentially causing stimulated follicles to 'run out of puff' before they are fully mature. The ultrashort protocol should not be used with pure forms of FSH, such as Fertinex, Gonal-F, Metrodin HP or Puregon, or poor egg quality will result if some luteinising hormone is not administered.