The following Mark's Daily Apple article was written by Mark Sisson, and is narrated by Tina Lehman.

Nine factors that influence testosterone levels.

In the last several weeks, testosterone has come up on a pretty regular basis,

but there's something about the novel elements in recent conversations that's kept the exchange going,

such as solar irradiation for certain choice body parts.

I thought I'd pull back from the peripheral findings a bit today

and re-center the discussion. As you know, testosterone plays a pivotal role not just for libido levels,

although we won't leave that out, but also for bone density, protein synthesis and muscle building,

hair growth, estrogen production, red blood cell production,

sperm production, amid other key functions in the body, for men and women, by the way.

So what are some factors that influence testosterone levels for the better and worse for both genders?

What are the mechanisms behind these associations?

And how do they relate to a healthy primal life?

Let's dig in.

Understanding the testosterone spectrum.

The first question that always comes up is what normal or desirable levels should be.

As with many of the measurements and markers we seek out, I tend to trust how I feel

more than what a single number in time reflects. It's one thing to suspect you might have a deficiency

based on symptoms, but it's another to talk lab values. Are you experiencing low energy,

low libido, breast development in men, expanding waistlines, infertility,

erectile dysfunction, bone weakness, genital numbness, depression, or reduced muscle mass?

Assuming poor lifestyle habits aren't behind these. My preference at this point would be

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