Low levels of testosterone and estrogen may cause problems for men, according to a new study released Thursday.
The study which was published in the New England Journal of Medicine claims that from 1993 to 2000, prescriptions for testosterone replacements increased fivefold, boosted by advertising campaigns that invited aging men to "talk to their doctor about low T" if they were experiencing decreased energy, sex drive or muscle tone.
However, physicians haven't really known just how low testosterone levels might produce these symptoms, and just how low testosterone would need to drop to cause changes in a man's energy level, his body composition or his sexual function. In fact, while men were lining up in droves to get tested for "low T," physicians and researchers really weren't sure whether the problem was testosterone at all.
It turns out that some of men's "low T" symptoms are, in fact, attributable to a deficiency of "the female hormone," estrogen. Low E, not low T, may be responsible for the decline in many men's sexual function and their accumulation of body fat.
The new research explored what mix of hormone levels in healthy younger men might bring on the hallmark symptoms of male hypogonadism: loss of energy and strength, sexual dysfunction and depressed libido and changes in body composition that add flab and sap muscle tone.
Because a portion of a male's testosterone is converted to the hormone estradiol--a form of estrogen--researchers knew there was more to the hormonal mix than just testosterone. So they recruited more than 300 healthy men between 20 and 50 and tinkered with their hormonal balance to see what the effects would be.
All the men had their testosterone hormone production suppressed by four monthly injections of the drug goserelin (marketed as Zoladex) and either a placebo testosterone replacement or actual testosterone replacement that ranged across four levels, from very little replacement to complete replacement.
