[fredr123]

http://sports.espn.go.com/mlb/news/story?id=4148907

Allegedly the drug in question was hCG (wikipedia explanation).

There's this:

In the world of performance enhancing drugs, hCG is increasingly used in combination with various anabolic androgenic steroid (AAS) cycles. It is included in some sports' illegal drug lists.
When AAS are put into a male body, the body's natural negative-feedback loops cause the body to shut down its own production of testosterone via shutdown of the hypothalamic-pituitary-gonadal axis (HPGA). It is a common misconception that estrogen will be elevated post cycle. Generally, estrogen is below a normal level after a cycle.[11] High levels of AASs that mimic the body's natural testosterone trigger the hypothalamus to shut down its production of gonadotropin-releasing hormone (GnRH) from the hypothalamus. Without GnRH, the pituitary gland stops releasing luteinizing hormone (LH). LH normally travels from the pituitary via the blood stream to the testes, where it triggers the production and release of testosterone. Without LH, the testes shut down their production of testosterone, causing testicular atrophy.
In males, hCG mimics LH and helps restore and maintain testosterone production in the testes. As such, hCG is commonly used during and after steroid cycles to maintain and restore testicular size as well as endogenous testosterone production. However, if hCG is used for too long and in too high a dose, the resulting rise in natural testosterone will eventually inhibit its own production via negative feedback on the hypothalamus and pituitary.

and then there's this:

In the male, hCG injections are used to stimulate the leydig cells to synthesize testosterone. The intratesticular testosterone is necessary for spermatogenesis from the sertoli cells. Typical uses for hCG in men include hypogonadism and fertility treatment.