Are you ready to put Super Laser Power to work for you? Are you ready for the Little Woman to once again be able to run her fingers through your hair once again? Well, it can happen for you. Most guys will probably tell you that the most humiliating part of aging is was losing those golden locks. So how can we regain lost youth from the tip of our toes to the top of our scalps?
Well, there's a right way and a wrong way to do it if you ask me. Most guys have heard of Proscar/Finasteride and Rogaine/Minoxidil as science-based hair loss solutions. However, what guys are not told, usually until it's too late, is that these have very nasty and fairly common side effects, including erectile dysfuntion and arrythmias, respectively. (See below for more details.) In addition, real life results seem to be significantly less than the studies. Consumer Reports found that only 27% and 4% of respondents felt that Propecia and Rogaine, respectively, were "very effective".. 
CAUTION: If you're currently taking medications, you should definitely check with your doctor or pharmacist if they could be causing or exacerbating your thinning hair. Many blockbuster drug categories, including angiotensins, beta-blockers, ACE inhibitors, diuretics and blood thinners, can negatively effect hair. 
So is there no hope for us with Scalp Dysfunction Syndrome? See my link on Hair Loss Factors for more natural solutions and protection.
Below I have outlined the approaches that have achieved good success in the research, although the pharmaceuticals are downright dangerous as I cover below:
Of course, surgical hair replacement is always an option to restoring your hair. It is, however, quite expensive, time consuming and physically uncomfortable. The hot new cosmetic technology involves firing up a good ol' fashioned laser beam and directing that right at the top of your head. (Actually, it's a bunch of laser beams.) Who would have thought that laser technology might one day turn you back into a rock star?
The treatment methodology is actually called LLLT, for Low Level Laser Therapy and produced solid results in one recent study where the number of hairs and the strength of existing hairs was increased.  What else could you ask for, eh?
It takes about a half dozen treatments to generally stop the progression of hair loss and a half dozen more until you start seeing those precious new buds breaking out of the soil. (If you've been bald for ten years, don't expect a miracle. This is for those who still have some warriors on the moutain top.)
Side effects are minimal, sometimes a little redness and tenderness, and that's about it. Treatments are usually done a few days or few weeks apart. The cost is not cheap - around $2,000 - $4,000 for a full year of treatments - but doable for many guys.
NOTE: The study showed that this was effective with both males and females.
Quite often in the world of health, the counterintuitive is actually correct. This applies to the case of caffeine as a hair growth stimulant. Caffeine is known as a vasoconstrictor, i.e. it decreases blood flow which is generally bad for hair growth. However, in vitro (lab/test tube) results show that caffeine is a potent stimulator of hair growth. Basically, one study removed follicles from the scalps of men with male pattern baldness (androgenic alopecia) and put them in a test tube with and without caffeine.  Those in the presence of caffeine grew much more rapidly.
Why, you may ask, am I losing my hair when I have a couple of cups of coffee every morning? Dr. Weil estimates that you would have to down 60 cups of joe to deliver enough caffeine to your hair follicles for this to work, so the only realistic solution is a topical one applied directly to the skin. 
Currently, there are several manufacturers creating caffeine shampoos that seem to be having some positive reviews. Revita is an example on Amazon: DS Labs Revita Hair Growth Stimulating Shampoo (2). And I have also read that there is a Swiss company making a line called Alpecin as well. There is a study that shows that shampoos can effectively deliver caffeine to the scalp, but so far there has been no study on whether or not caffeine actually gets rid of male pattern baldness or not. In the meantime, you can try it if you like...
A small, but well-designed study showed that a combination of saw palmetto and beta-sisterol results in 60% of patients with improved hair growth.  These are high numbers, indeed, and saw palmetto likely will help with enlarged prostate and other male issues as well. Life Extension, for example, puts together a product that clearly tries to target this study, i.e. it contains both extracts of saw palmetto and beta-sisterol. CAUTION: Although side effects are much less pronounced than Proscar or Propecia, some men report some loss of erectile strength and other similar side effects while using Saw Palmetto.
One study demonstrated that ketoconazole, the primary active ingredient in Nizoral Shampoo, can maintain hair and actually increase its thickness, strength and thus negate the "thinning" effects of aging.  Can it actually grow hair? So far the only evidence for that is one study on mice. 
Of course, Zinc can potentially boost testosterone and reduce estrogen. But did you know that one form of zinc may be able to put hair on your head as well. Yes, indeed, one study shows real, live, actual hair growth from use of a zinc pyrithione shampoo.  Both Selsun and Head and Shoulders make products with this ingredient: Head & Shoulders and Selsun Salon Pyrithione Zinc Dandruff Shampoo. Better buy a blow dryer and brush while you're at it.
Any discussion of legitimate hair loss treatments has to begin and end with Finasteride, i.e. Propecia or Proscar Lite, because it's hard to beat its clinical results. For example, one study shows that 80% of men were helped with additional hair regrowth is actually achieved.  In this same study it beat Minoxidil's 50% cure rate rather handily.
The problem with finasteride is that it works too good: it lowers DHT throughout the body when, in actuality, all that is needed is for DHT to be lowered in the scalp. This lowering of DHT systemically can cause muliple side effects for guys. In fact, the side effect profile gets rather ugly rather quickly:
FINASTERIDE SIDE EFFECTS: The biggest concerns with finasteride, a.k.a. Propecia or Proscar, are erection-related and pregnancy-related. First of all, every decent source that I know of warns against a pregnant woman coming into any kind of contact with this drug as the data strongly suggests that it can cause birth defects in the male fetus. This is scary indeed, because the majority of guys using finasteride are with females who are capable of becoming pregnant even if the likelihood is remote.
The other concern with finasteride is the commond side effect of erectile dysfunction and loss of libido. One study reported the percentage of men with such side effects to be about 15%, which is a very high number indeed.  However, this documented that there is a strong "nocebo" effect from doctors warning that "this drug may cause loss of libido and impotence". Apparently, those words from a doctors can create quite the negative effect in many guys!
The well-known PLESS study reported a smaller figure of about 8% in the first year decreasing to 5% in years 2-4.  In fact, what is interesting is that 5% was also reported by the placebo group and so we are left the counterintuitive finding that fnasteride start out with a negative side effect that essentially disappears after a year or two.
And that's not the end of the story. About one in fifty men on Propecia will experience permanent erectile loss due to androgen deficiency and/or resistance. This amounts to chemical castration and I cover the symptoms and one's readers description of it in my link on The Risks of Propecia.
Studies show that number 2 in the hair repair category has got to be Minoxidil (Rogaine).  Minoxidil induces hair growth in the 30%-50% range and thus is quite effective and with greatly reduced side effects when given in a 5% topical solution. Minoxidil also has the significant advantage of being over the counter.
What about side effects? Interestingly enough, minoxidil actually got its start as a blood pressure medication. It appears to mimic your friend and mine, Nitric Oxide, and derive its magical powers from the same. The side effects, when used for hypertension, are somewhat scary, including edema in about 7% of patients and altered brain waves. 
However, when applied topically on the scalp, the side effect profile is very low - please read the Caution section below! - with by far the most common reported issue being dryness of the scalp and/or or dandruff. The reason for this is probably that minoxidil must immersed in a base of alcohol and/or propylene glycol, both of which can cause drying of the skin. You can combat this oftentimes by simply using one of the shampoo/conditioner combos that tend to moisturize the scalp.
CAUTION: Minoxidil, in tablet form, is actually a powerful antihypertensive agent and, as such, can cause drops in blood pressure and irregular heartbeats. This is less common with topical applications on the scalp but can definitely occur. Discuss immediately with your doc if you have any such symptoms. I personally shy away from minoxidil, because it is notorious (in tablet form) for increasing heart attack risk in lab animals.  That same study found that minoxidil actually changed the ventricular (heart chamber) weights and coronary artery occlusions. Again, these changes in the heart are not supposed to happen with topical minoxidil but does in some guys using only a lower dose 2% solution. . "Don't mess with Mother Nature", I always say, "unless you really know what you are doing" and this is an example where we don't understand everything yet. By the way, minoxidil is a potassium channel opener as well. Who knows what effect that will have over decades of use??
However, there is one big turnoff for some guys: the twice a day application with no showering for four hours afterward. That's right - you have to apply this morning and evening and then let it sit for four hours, which is a significant time commitment and can, depending on your hair, leave an oily look.
Some people will also be disturbed by the very non-natural propylene glycol, but this is much less problematic than ethylene glycol, bettter known as antifreeze. In fact, propylene glycol is actually a food additive and used in many household products as well. Studies show no toxicity or cancer-causing effects except at very high doses.
Several studies have shown that when you combine the active chemical in Retin-A with Minoxidil, superior results are achieved.  In fact, one study showed hair regrowth in 66% of subject which is at finasteride levels.  Researchers believe this is because the Retin-A increases absorption of the minoxidil, allowing it to be more effective.
This has been combined in a product called MinSaw-A and marketed as such. I do not know a cheap way to obtain this product, but mention it. Again, see the warnings for minoxidil above.
1) Dermatology, 2004, 209(2):117-25, "An open, randomized, comparative study of oral finasteride and 5% topical minoxidil in male androgenetic alopecia"
2) Sexologies, 17(1):S102, Apr 2008, "T07-O-05 Finasteride 5 mg and sexual side effects. How many of these are related to a nocebo phenomenon?"
3) N Engl J Med 338:557, 1998, "The effect of finasteride on the risk of acute urinary retention and the need for surgical treatment among men with benign prostatic hyperplasia. Finasteride Long-Term Efficacy and Safety Study Group"
4) J Am Acad Dermatol. 2007 Nov;57(5):767-74, Epub 2007 Aug 29, "A multicenter, randomized, placebo-controlled, double-blind clinical trial of a novel formulation of 5% minoxidil topical foam versus placebo in the treatment of androgenetic alopecia in men"
6) Am J Clin Dermatol. 2007;8(5):285-90, "Efficacy of 5% minoxidil versus combined 5% minoxidil and 0.01% tretinoin for male pattern hair loss: a randomized, double-blind, comparative clinical trial"
7) J Am Acad Dermatol. 1986 Oct;15(4 Pt 2):880-3, 890-3, "Topical tretinoin for hair growth promotion"
8) J Altern Complement Med, 2006 Mar;12(2):199, "A randomized, double-blind, placebo-controlled trial to determine the effectiveness of botanically derived inhibitors of 5-alpha-reductase in the treatment of androgenetic alopecia"
11) Hypertension, 2001, 37(2):209-215, "Mortality after coronary artery occlusion in different models of cardiac hypertrophy in rats"
13) International Journal of Cosmetic Surgery and Aesthetic Dermatology, Aug 2003, 5(2):113-117, "Hair Regrowth and Increased Hair Tensile Strength Using the HairMax LaserComb for Low-Level Laser Therapy"
14) "Ketoconazole Shampoo: Effect of Long-Term Use in Androgenic Alopecia", http://www.hairlosstalk.com/hair-loss-pdf/nizoral-study.pdf
15) J Dermatol, 2005, 32 (4):243-247, "Topical Application of Ketoconazole Stimulates Hair Growth in C3H/HeN Mice"
16) Br J Dermatol, 2003 Aug, 149(2):354-62, "The effects of minoxidil, 1% pyrithione zinc and a combination of both on hair density: a randomized controlled trial"
17) WebMd Magazine, Jun 2010, p. 13.
18) Prevention, May 2010, p. 16.