A high percentage of men have varicoceles - somewhere around 15 to 20 percent  - and yet, from what I have seen on the Peak Testosterone Forum, it is infrequent that urologists wish to repair them. This is tragic, because in many cases varicocele procedures can make a significant difference in testosterone levels and in how they feel. In fact, one of our senior posters (Sam) on the Peak Testosterone Forum, noted that fixing his varicocele made a huge difference in how he felt even though he got no significant increase in testosterone.
STEP 9: For this reason I have included taking care of a varicocele as a step in my Peak Testosterone Program. (For the other steps to the program, see my Home Page.) Of course, varicocele procedures aren't going to help all men, but they will definitely significantly help a big percentage and will help with some of the symptoms that seem to plague us guys in modern societies, such as low libido, poor sleep, lack of energy and low levels of various hormones. And, again, what is particularly remarkable is that some doctors will tell their patients that a varicocele procedure will not improve testosterone or their health in general, when, in fact, there are multiple studies that show just the opposite.
As an example, look at what this M.D. wrote about varicoceles:
"If a teenager or young man with a varicocele has a smaller than normal testicle on that side, there is an increased risk of infertility and many urologists consider this an indication to fix the varicocele surgically. Rarely, a varicocele may lower the testosterone level. In this instance, the testes are usually smaller than normal. Such a circumstance may decrease the libido. Evaluation of the serum free testosterone level can detect this." 
Rarely?!? I just do not understand why a doctor would make such a claim when there are a number of studies that say just the opposite. Let's look at some of the research about varicoceles and what repairing them can do for you along with some of the experiences of men on the forum:
1. Increased Testosterone. Will every man get an increase in testosterone? Of course not. Nevertheless, the studies show very powerfully that most men likely will:
a) Infertile Men. One study showed that testosterone levels in infertile men increased from 319 to 409 ng/dl, a nice 28% increase on average. The authors noted that "men with at least 1 firm testis preoperatively had a greater increase in serum testosterone." 
b) Using Microsurgery. Another urologist did a larger study on any man with a varicocele and found that every age group had lower testosterone than their non-varicocele counterpart cohorts. Furthermore, after varicocle surgery, 70 percent of the men experienced an increase in testosterone. So much for the theory that repairing a varicole does not affect testosterone!
c) Nice Increase. Yet another study showed that men got a boost of 110-146 ng/dl from varicocele repair. This is not going to correct hypogonadism in anyone, but is an impressive increase nonetheless. 
NOTE: One of our senior posters on the Peak Testosterone Forum had a lot of great tips and commentary regarding his varicocele procedure and the process of finding a good physician, etc. You can read his commentary here.
2. Increased Sexual Activity. One study on men with fertility issues found that couples had greatly increased intercourse rates post-varicocele: "the improvement of sexual activity was 50-75%, the pregnancy rate for their partners was 37% and increased plasma testosterone levels over a period of 3 years of follow-up after varicocele repair." 
3. Increased Libido and Energy. Let me quote one urologist: "a varicocele repair can help increase testosterone, improving energy level, sex drive, and the ability to have an erection." 
4. Greatly Improved Sleep. Why would libido and energy improve? One reason may be sleep. Look at what Sam wrote, one of our regular posters:
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"If you are a middle aged man and suffering from insomnia and low t make sure you don't have a varicocele. While completely subjective and based entirely on my own personal experience, within 1 week of having my varicocele repaired I was sleeping through the night and haven't had a bad nights sleep since. Coincidence?"  "I did and it had no impact on t levels but major improvements in sleep. Basically I went from waking up 3-5 times a night to sleeping through the night totally again." 
5. Normalized Body Temperature. Sam also noted something very interesting that indicates normalized thyroid function:
"So I was contemplating on how my average body temp went from an unstable but consistent 97.4ish to a steady 98.6 within a week of my varicocele procedure and it got me wondering if the body would down regulated your body temp if a varicocele was causing your gonads to operate at too high of a temperature. If so this could be a way for men to tell if they have a varicocele that is impacting testicular function." 
6. Fertility. Correcting even a unilateral (one testicle) varicocele can make a very significant change in fertility. For example, one study wrote, "Preoperatively, men with grade 3 varicocele had lower sperm counts and poorer fertility indexes compared to men with grades 1 and 2 varicocele. Sperm concentration improved significantly in men with grade 2 (33 +/- 5 million per cc preoperatively to 41 +/- 6 million postoperatively) and grade 3 (18 +/- 5 million preoperatively to 32 +/- 7 million postoperatively) varicocele after microsurgical ligation of the varicocele. Motility improved significantly in men with grade 3 varicocele." 
4) J Urol, 1993 Apr, 149(4):769-71, "Relationship between varicocele size and response to varicocelectomy"
5) Systems Biology in Reproductive Medicine, 2003, 49(3), IMPROVEMENT OF SEXUAL ACTIVITY, PREGNANCY RATE, AND LOW PLASMA TESTOSTERONE AFTER BILATERAL VARICOCELECTOMY IN IMPOTENCE AND MALE INFERTILITY PATIENTS"
7) The J of Urol, 154(5):1752-1755, "The Effect of Varicocelectomy on Serum Testosterone Levels in Infertile Men with Varicoceles"