Human Chorionic Gonadotropin injections.

Human chorionic gonadotropin (hCG) is a form of treatment used by both male and female patients with Kallmann syndrome and CHH.

In females it is used primarily in fertility treatments.

For males it can be used for testosterone production on its own or as part of fertility treatments. A common trade name for hCG is "Pregnyl", other formulations are available as well as generic forms.

hCG has the same activity as the pituitary hormone, LH, which stimulates testosterone production by the testicles. In men with Kallmann syndrome or CHH the levels of LH produced by the pituitary gland are very low or even zero.

hCG is the hormone that is produced by placenta during pregnancy. It forms the basis of pregnancy test kits. While hCG is not a hormone that is normally found in males it is safe to be given to males in low doses for this type of treatment.

hCG acts on the Leydig cells within the testicles and induces them to produce their own testosterone. This treatment can be taken instead of taken testosterone replacement therapy. 

Dosage and intervals will vary but normally injections are taken twice a week, sub-cutaneously (sc), just under the skin. It can take from 2 to 4 weeks for the testicles to start producing testosterone. The doctor might adjust the dosage according to the testosterone levels achieved. The testicles might increase in size a little while on hCG treatment but it is normally not a big increase.

Some men with Kallmann syndrome / CHH can achieve fertility while taking hCG injections alone, especially if they have been on fertility treatment in the past. However most will require an additional type of injection used in conjunction with hCG to achieve sperm production.