Testosterone is required for hundreds of functions in the male body. In general it is a necessary component of libido, converts to estrogen which is required for bone and joint health, required for limbic system health and many other functions. Deca does not convert to estrogens at a significant rate and the estrogens it does convert to are 19-nor. Dianabol converts to 17 methyl forms of estrogen and are again not natural. ON a deca/dianabol cycle you will be deficinet of testosterone, dihydrotestosterone and importantly also natural estrogens. Additionally, nandrolones are potent progesterone receptor agonists. In practical terms what this means is the libibo can be very negfatively affected. It is not known exactly why this is the case. it is thought that prolactin in increased either systemically or locally in the brain leading to the satiated feeling that occurs after sexual activity but does not subside. This appears to be treatable with Dopamine D2 receptor agonists such as Cabergoline and pramipexole. But hey, why put up with these problems. Just use a test base and probably stay away from nandrolones.