I've been using Fenugreek as a male for years and I can verify a few things;
*Fenugreek will give you a maple sweet body odor, acting as a natural deodorant, however you will cease to notice this similarly to not noticing the smell of your house after about two three weeks of usage.
*Fenugreek does lower blood sugar, after taking a large amount, 20-30 grams or more I find myself strangely hungry despite having a full stomach in many cases.
*Fenugreek has some action on stimulating LH Luteinizing hormone and therefor BOTH testosterone and estrogen, in the quantities the body wants it. This has the opposite side effect of taking steroids (testicular atrophy) but the amounts of testosterone in circulation will not exceed demand. It is not a way to increase testosterone just normalize it by force.
The danger in this is, theoretically, that the body is producing something it does not think it should be making. There are controls in place to stop the production of hormones for various reasons, the most relevant one being because there are not enough resources.
Therefor; I stress to all males interested in the effects (my testicles have certainly grown, you can find many testimonials to the seed and formulations of the seed likewise on the internet) to first make sure they have more than enough food, lest they risk whatever dangers arrive from the body producing things with resources it doesn't have.
*Fenugreek is sproutable to a 1-2cm tail within 24 hours.
As a side note, I would personally attribute all effects to the stimulation of LH. Testosterone will lower blood sugar and make you hungry, estrogen will make you produce more milk etc. The compounds assumed to have this action have been isolated as saponins, extract of which is usually referred to as "furostanol saponins"
I have not noticed any side effects however a rational assumption is that if someone is suffering from estrogen dominance as a male or visa-versa, this will just aggravate the symptoms as LH will only produce what hormones are called for.