Testosterone, Prolactin and Prolactinomas
Some hormones just don't tend to play well with your testosterone. Cortisol
and estrogen are examples. Another hormone that can whack your
testosterone and your sex life is prolactin.
Prolactin is a fine hormone and great for sleep, but, unfortunately, it makes
a lot of other important things go to sleep, including your
testosterone and fertility if levels are high enough. It is, not too
surprisingly, often devasting to erections due to decreased testosterone levels and
because it antagonizes dopamine and leads to an increased refractory (recovery
post-erection) period.  Excessive
prolactin is also associated with gynocomastia,
i.e. "male boobs". 
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In females, hypothyroidism is a common cause of elevated prolactin levels.
In males, hypothyroidism likely raises prolactin but not as significantly. 
In my mind, I never understood why prolactin is not pulled more commonly in men
with low testosterone. The justification for rarely testing seems to be
based on a cost and efficiency basis, but those kind of arguments are always
weak if you are the one with the condition, eh? I cannot help but wonder
how many men are walking around have low testosterone due to elevated prolactin
and the treating physician has absolutely no idea.
Consider the fact that one study noted that previous research found an "overall
prolactin greater than 20 ng./ml. in 1.86% of 1,821 patients, prolactinomas in
7, 0.38%." but found only five out of about a thousand men had prolactin
exceeding 20, i.e. about 0.5%.  In other words, high prolactin is
generally not a root cause of low T, but it certainly can be and at a rate of
somewhere around 1 out of a 100 hypogonadal men. However, the researches
still concluded that "prolactin should be determined only in cases of low sexual
desire, gynecomastia and/or testosterone less than 4 ng./ml." This is an
amazing statement because it recommends that prolactin be pulled for
testosterone less than 400 ng/dl, something that is simply NOT done from all I
have seen. My impressions from the
The Peak Testosterone Forum is that probably one out of
every ten men has their prolactin pulled.
NOTE: You can have very high prolactin and yet still not be hypogonadal.
The same study found that "testosterone was low in less than 50% of cases with
prolactin greater than 35 ng./ml." 
So how do males get very elevated levels of prolactin then? One all-to-common
cause is a prolactinoma, a benign tumor of the pituitary that begins secreting,
sometimes in great quantities, prolactin. This can have devastating effects.
Look at the description of this reader in his mid 40's:
"I started experiencing longer and
longer periods between being able to have sex
starting about 4 years ago. It is to the point now
that I don't know when I can get it up. It has
been very hard on my marriage and my wife has since
moved out because she felt unloved and unattractive
because of my lack of sexual desire. As you can
imagine now that she has moved out I am taking
this very serious. Here are my issues. I was going
to a family doctor and wasn't liking
the results I was getting. He told me I had low
testosterone and put me on Andogel packets"
His low testosterone was devastating as you can tell. How tragic that a physical
malady could lead to the undoing of a marriage. However, he did write me
back with some good news:
"Are you sitting down for my Prolactin reading? It was 200. Normal from
what the doctor told me is 1 - 12. This is suppose to be curable from what I
have heard so I am very exited as you can imagine. Thanks again."
Elevated prolactin is very anti-testosterone and often lead to hypogonadism.
His levels were astronomical and and thus it is not surprising that his testosterone was so
adversely affected. (He was correct, of course, that normal prolactin
levels are less than 12 ng/ml or maybe 15 ng/ml.) In his case, they did not find
a prolactinoma or other tumor from an MRI, but put him on the standard
medication and he got immediate results.
So, if you are wondering where your testosterone levels went, you may want to ask
your doctor about getting a prolactin reading.
CAUTION: Read my link on The Importance of Avoiding Excitotoxins.
Animals studies show that prolactin levels can be negatively affected due to
excitotoxin damage to
the hypothalamus. In addition, minoxidil is suspected of causing prolactinomas
and elevated prolactin levels.  Minoxidil (Rogaine) is a common
over the counter hair loss treatment.
The American Journal of Medicine, May 1978, 64(5):782-787, "Serum prolactin
levels in untreated primary hypothyroldism"
2) Psychiatr Serv, 51:983-985, Aug 2000, "Psychopharmacology: Galactorrhea and
Gynecomastia in a Hypothyroid Male Being Treated With Risperidone"
3) N Engl J Med 1978; 299:847-852, "Prolactin-Secreting Tumors and Hypogonadism
in 22 Men"
4) Rev Urol, 2000 Winter, 2(1):39–42, "Hyperprolactinemia and Erectile
6) The Journal of Urology, 1997, 158(5):1764-1767, "Endocrine screening in 1,022
men with erectile dysfunction: clinical significance and cost-effective