The New Science of Male Sex Drive

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How to Boost Libido​

Not feeling as frisky as you used to? It's about more than testosterone levels. Here's how to get your mojo back.​

Male sex drive is largely influenced by testosterone. The more testosterone you have, the thinking goes, the more likely you are to get horny. However, according to a recent study, total testosterone has little to do with male libido. Instead, it's free testosterone and, surprisingly, the ratio between testosterone and estradiol (a type of estrogen) that determines how worked up you get.

The Sex Drive Study​

The scientists had 200 patients of a cardiology practice fill out a series of erectile dysfunction questionnaires, including the IIEF-15, which collectively paint a pretty clear picture of a man's libido. None of the men were diagnosed with hypogonadism (low testosterone), and none were on medications that could affect T levels.

The researchers then measured the patients' total testosterone, estradiol, sex hormone-binding globulin (SHBG), and free testosterone and compared them with their reported libidos.

What They Found​

They found no correlation between total testosterone and how often (or how infrequently) the men wanted to have sex. Nor did estradiol levels correlate independently with sex drive, even when levels were lower than 5 ng/dL. That's significant because it was thought that men are more likely to have healthy libidos if their estradiol is in the "sweet spot" between 2.0 and 5.5 ng/dL.

What did correlate with libido, though, was the ratio of testosterone to estradiol, along with free testosterone: that percentage of testosterone that isn't chemically bound to SHBG. The higher the free T, presumably the greater the sex drive.


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What This Means To You​

Often, men with low libidos or poor sexual functioning go on testosterone replacement therapy. Sometimes it works and sometimes it doesn't. When it doesn't, it's generally because of one of these things:

• Too much SHBG (resulting in low levels of free testosterone)
• High estrogen levels (throwing off the testosterone/estrogen ratio)

What the study didn't tell us is the perfect level of free testosterone or the precise T:E ratio we'd want for an "optimum" sex drive. Still, it gives us some clues. First, know the signs of low T or high E.

• Symptoms of low testosterone: Depression, weight gain, inability to put on muscle, diminished sexual desire or performance.
• Symptoms of high estrogen: Increased abdominal fat, fatty tissue around the nipples, erectile dysfunction, or loss of libido.

If you have any of those symptoms, find a progressive physician and get your SHBG and estrogen levels tested (along with free T), the latter with what's known as the "sensitive" assay. Your other choice is to experiment with using dietary practices and supplements to manipulate levels of SHBG and estradiol.

How to Lower SHBG and/or Raise Free Testosterone​

• Take chelated magnesium daily to raise free testosterone. Take chelated zinc daily to lower SHBG.