The effects of cannabis are non-toxic.

According to the Australian reports from the late 1990's, the ones that were found to be erroneous, higher testosterone levels were found in heavy cannabis users (40 males studies).

You know of the studies showing a very small affect in learning and memory, but, not enough to be considered anything and tests showed no effects had any impact after 28 days. (by the way, these are recent, I don't have time, right now, to look through my bookmarks for the site)

Pile onto that, this:
Quote Originally Posted by http://www.counselingseattle.com/drugs/steroids.htm
Anabolic Steroids
Affect the Brain

Parts of the brain that influence your moods and are involved in learning and memory are called the limbic system. Anabolic steroids act in the limbic system. In animals, they have been shown to impair learning and memory. They can also lead to changes in mood, such as feelings of depression or irritability.

Anabolic steroid users may act mean to people they're normally nice to, like friends and family.

Anabolic steroids in the brain may trigger really aggressive behavior. Some outbursts can be so severe they have become known in the media as "roid rages."
And this...

Quote Originally Posted by http://www.cmaj.ca/cgi/content/abstract/166/7/887
for seventy 17- to 20-year-olds through self-reporting and urinalysis. IQ difference scores were calculated by subtracting each person's IQ score at 9â??12 years (before initiation of drug use) from his or her score at 17â??20 years.

Current marijuana use was significantly correlated (p < 0.05) in a dose- related fashion with a decline in IQ over the ages studied. The comparison of the IQ difference scores showed an average decrease of 4.1 points in current heavy users (p < 0.05) compared to gains in IQ points for light current users (5.8), former users (3.5) and non-users (2.6).

Current marijuana use had a negative effect on global IQ score only in subjects who smoked 5 or more joints per week. A negative effect was not observed among subjects who had previously been heavy users but were no longer using the substance. We conclude that marijuana does not have a long-term negative impact on global intelligence. Whether the absence of a residual marijuana effect would also be evident in more specific cognitive domains such as memory and attention remains to be ascertained.
Studies have shown that teen-use of marijuana can be detected later in life, especially, in anxiety issues.

Honestly, I don't think Cannabis affects the hypothalamus, other than the CB1 receptors, and that area of the brain produces testosterone.

As with all drugs, Cannabis will deaden the reinforcement properties of the other drug involved.

Quote Originally Posted by same ^
In guys, anabolic steroids can interfere with the normal production of testosterone. They can also act directly on the testes and cause them to shrink. This can result in a lower sperm count and reproductive ability. They can also cause an irreversible loss of scalp hair.

In girls, anabolic steroids can cause a loss of the monthly period by acting on both the hypothalamus and reproductive organs. They can also cause loss of scalp hair, growth of body and facial hair and deepening of the voice. These changes are also irreversible.
"You may have heard that doctors sometimes prescribe steroids to reduce swelling. This is true, but these aren't anabolic steroids. They're corticosteroids."

I feel like I haven't answered your question, but I've been kind of busy, and in a hurry, so I'll tell you what I think.

1st- If you're gonna use steroids, don't tell people you smoke pot.
2nd- If you're a teenager, smoking pot, lightly, seems to be okay, as long as you persist on it (see CMAJ study above), but those tiny, little residual effects will be exacerbated by the steroid use, and very greatly in younger users.
3rd- I'm really pushing it, time-wise.
4th- I'll check back.