STEP 4B. Is low testosterone (and the ensuing low estradiol) causing you bone loss? osteopenia? osteoporosis?
What does testosterone have to do with your bones? Surprisingly, testosterone plays an indirect but very significant role in bone health for males. In fact, one common and potentially dangerous symptom of hypogonadism is osteopenia and osteoporosis. Yes, men can suffer from osteoporosis with the associated hip fractures and spinal problems just like their wives and girlfriends.
One of our oldest members (Starry) on The Peak Testosterone Forum had osteopenia and wrote:
"I was pretty shocked when he did my bone density last month...."osteopenia in the spinal column" it read. I'm not in my 20's but I'm not old either! work out hard, exercise, eat right, etc, and here i am with essentially pre-osteoporosis. Yikes. Just another reminder of the insidious things low T (my counts in lower 200s) can do. He made sure to tell me to immediately start on at least 500 milligrams of calcium a day. Really anticipating my T level and estrogen/estradiol results next week after 5 months on Clomid." 
Like Starry, most men do not realize is that the root cause of their low estradiol is actually low testosterone. Remember that estradiol in men comes from testosterone through a conversion process centering around the aromatase enzyme. While itï¿½s true that too much estrogen can be a problem for some males, it is equally possible for a manï¿½s testosterone to fall so low that estradiol in turn plummets to dangerously levels because there is just isn't enough baseline T to convert to E2. This is when net bone loss can begin to occur and, as the years go by, osteoporosis and all of its medical complications can set in.
Just how serious is this issue? Researchers studied a group of men over 60 and controlled for all the standard osteoporosis risk factors. They found that low total testosterone was strongly correlated to bone loss and associated with an 88% increased risk of hip and 28% of non-spinal fractures, respectively.  Obviously, when your bones begin fracturing, this becomes both painful and debilitating.
At what testosterone level did this become a problem? The researchers broke the study participants into quartiles and found that the lowest quartile, which was total testosterone less than 291 ng/dl (9.9 nmol/l), had the highest fracture rates. (NOTE: The lowest quartile of estradiol (E2) was less than 13.9 pg/ml.) Men who suffer from osteoporosis can also find themselves with other debilitating conditions, such as joint issues and compressed spines.
Just how serious is this issue? Researchers studied a group of men over 60 and controlled for all the standard osteoporosis risk factors. They found that low total testosterone was strongly correlated to bone loss and associated with an 88% and 28% increased risk of hip and non-spinal fractures, respectively.  Obviously, when your bones begin fracturing, this becomes both painful and debilitating.
What about osteopenia? Many low testosterone men are now diagnosed with osteopenia instead of osteoporosis. Osteopenia is basically bone density that is analogous to prehypertension. It is indicating bone loss but not as severe yet as traditional osteoporosis. Should you take it seriously? Yes! One of our forum posters wrote "Because I am on steroids for the next month or so and was diagnosed with osteopenia some years ago, possibly from steroid use or from colitis." 
As expected, testosterone therapy helps significantly. One study looked at senior men (about 65 years old and not necessarily with osteoporosis) and found that if they started with total testosterone levels of about 200 ng/dl (6.8 nmol/l), testosterone therapy significantly increased their bone mass. The study encompassed three years and the menï¿½s average peak testosterone went from 367 to 625 ng/dl. 
Just how common is osteoporosis in men with low testosterone? Well, in men with testosterone < 200 ng/dl, which is VERY low T, 12.3% of men were found to be osteoporotic.  That's roughly one in eight and thus is a significant percentage. Furthermore, the studies, as far as I know, have not looked at the prevalence of osteopenia among hypogonadal men and this would undoubtedly be a substantially higher percentage.
I should mention that not all the research has shown this relationship. In fact, one interesting study showed that testosterone levels were not really associated with osteoporosis and that it was SHBG that was the true correlate instead.  Yet another study showed that it was really estradiol that was critical and not testosterone, which is not too big of a shock. For a good summary of the studies, see this research summary for more information. However, since our estradiol comes from testosterone, it is somewhat of a moot point. Obviously, this is yet another reason that low testosterone can be an indirect root cause of osteoporosis in men and should be taken very seriously
NOTE: Low estradiol should be taken seriously for many other reasons as well, including negative effects on sexual, cardiovascular and brain health. See my link on Why Men Need Adequate Estrogen for more information.
Of course, ramping up your testosterone is key if that is the root cause for your bone loss. Other critical factors to regaining your bone density are ample calcium, Vitamin D, magnesium and exercise. Do not go overboard with calcium without discussing with your physician, as it has been linked to several kinds of cancer. Also, I highly recommend you get your Vitamin D check if you have not already as it can lead to low testosterone. See my links on Prostate Cancer Prevention and Vitamin D for more details.
1) Arch Intern Med, 2008, 168(1):47-54, "Endogenous Sex Hormones and Incident Fracture Risk in Older Me: The Dubbo Osteoporosis Epidemiology Study"
2) J Clin Endocrinol Metab, 1999 Jun, 84(6):1966-72, "Effect of testosterone treatment on bone mineral density in men over 65 years of age"
4) The Journal of Clinical Endocrinology & Metabolism, Oct 1 2006, 91(10):3908-3915, "Association of Testosterone and Estradiol Deficiency with Osteoporosis and Rapid Bone Loss in Older Men"
5) Bone, 2001 Jul, 29(1):90-5, "Osteoporosis in men: a potential role for the sex hormone binding globulin"
6) Clinical Endocrinology, Apr 1999, 50(4):411-414, "The effects of testosterone on osteoporosis in men"