One of the members on the Peak Testosterone Forum really got my attention one day when he posted that his testosterone had more than doubled from taking a medication called Naltrexone. Naltrexone is an opiod receptor antagonist that is typically used in the treatment of drug and alcohol addictions. It is a very interesting medication, but what caught my eye was the fact that this poster said his testosterone went from 400 ng/dl to 1,000 ng/dl! 
Not bad, eh? Well, I think that synthetic pharmaceutical solutions should be a last resort, but there may be a less to be learned here. Below I want to summarize the various pathways tat Naltrexone works on, but first let's look at some interesting study results with Naltrexone that pertain to men's health and/or hormones.
1. LH (Leutinizing Hormone) Protection. Normally heroin administration causes a big drop in LH (leutinizing hormone), which affects testosterone negatively. However, Naltrexone protects against any such drop in LH. 
2. Testosterone Restoration. One study found that administration of heroin significantly lowered testosterone levels - as expected of course - and that Naltrexone restored it into the medium high range.  However, these results do not appear to be replicated in normal males. See the next item:
3. Erectile Dysfunction Aid. A fairly recent study look at 30 men with 1 year plus of idiopathic erectile dysfunction.  This means that doctors did not know the cause of their E.D. nor could they solve it. Look at the results that were achieved:
"The naltrexone therapy significantly increased the number of successful coitus compared to placebo after 7 and 15 days of treatment: improvement of sexual performance was evident in 11 out of the 15 treated patients. All the patients experienced a significant increase in morning and spontaneous full penile erections/week. No significant side effects were reported."
The authors commented that testosterone was NOT increased. So Naltrexone did its magic without the help of the Power of T. What is even more remarkable is that fully one third of the patients who had already discontinued Naltrexone treatment had their erectile strength completely restored!
UPDATE: LDN may have worked by upgrading eNOS according to this study. The researchers stated that "Conversely, the activity of NOS was increased by the ï¿½-receptor antagonist, naltrexone." 
Protecting testosterone and (often) curing unsolvable erectile dysfunction are pretty impressive results to say the least. However, this is just the beginning of some of Naltrexone's extraordinary abilities: it also has the ability to greatly help with autoimmune thyroid disease according to an underground, alternative health movement. The treatment protocol is called "LDN" for Low Dose Naltrexone therapy and it seems to work remarkably well in patients who with the VERY common autoimmune thyroid disorders - Grave's and Hashimoto's. 
NOTE: It also reportedly helps many people with lupus, Crohn's and other autoimmune condition. 
So now let's go back to the this Peak Testosterone Forum post where the poster said that he more than doubled his testosterone. In his case, he had Hashimoto's with significant antibodies and the Low Dose Naltrexone dramatically reduced his counts. Of course, this is going to be good for his thyroid as well. So Naltrexone, at least in some men, will have a doubling effect, because it is both helping lower an immune reaction and improving thyroid function. Now studies show that if you correct hypothryoidism, you can boost testosterone around 30%, nowhere near the 150% increase of this poster. However, for some reason, in this man his testosterone went through the roof with the combination. (I don't advocate self-treating as this man did. You should always be able to find a physician, naturopath or other practitioner who will work with you.)
NOTES: It is true that in a study on monkeys, males on Nalterexone "significantly reduced sexual behaviour in previously active males, while increasing grooming interactions."  In other words, these monkeys got themselves all ready for the party, but then never showed up! The authors commented that this was the opposite of that reported in rodent studies. A recent rodent study showed that Naltrexone kept males from losing interest during stressful situations.  This appears, for whatever reason, to be the exact opposite case for human males however. In addition, Naltrexone increased prolactin in some male monkeys. However, in this study prolactin was increased only in those males that were lower prolactin in the first place.  So, although higher prolactin levels mean decreased testosterone and libido, in this case one could argue it re-established normalcy.
CAUTION: Low dose naltrexone appears to be pretty safe in the short term. As far as I know, long term studies have not been done nor long term safety established.
2) Pharmacology Biochemistry and Behavior, Nov 1980, 13(5):663ï¿½672, "Behavioural and endocrine effects of naltrexone in male talapoin monkeys"
3) Psychoneuroendocrinology, 1976, 1(4):359ï¿½369, "Acute effects of heroin and naltrexone on testosterone and gonadotropin secretion: A pilot study"
4) Physiology & Behavior, Feb 2009, 96(2):333-342, "Naltrexone effects on male sexual behavior, corticosterone, and testosterone in stressed male rats"
5) JPET, Sep 1980, 214(3):503-506, "Heroin and naltrexone effects on pituitary-gonadal hormones in man: interaction of steroid feedback effects, tolerance and supersensitivity"
6) Psychoneuroendocrinology, 1989, 14(1-2):103ï¿½111, "Endorphins in male impotence: Evidence for naltrexone stimulation of erectile activity in patient therapy"
8) Proc Natl Acad Sci U S A, 1999 Feb 16; 96(4): 1722ï¿½1726, "ï¿½-Endorphin blocks luteinizing hormone-releasing hormone release by inhibiting the nitricoxidergic pathway controlling its release"