You make a lot of sacrifices when you become a parent -- but this is one I'm sure most men never see coming...

It's the loss of their manhood.

No, I'm not just talking about the fact that one-time tough guys will coo at a baby, or decorate a nursery in pink.

I'm talking about real research that reveals a sharp dip in testosterone levels from the moment they hear the words, "It's a boy!"

Fatherhood can literally cause testosterone levels to plummet by as much as half the moment a child is born. And while it recovers after that (a little bit, anyway), they never quite get their pre-parental mojo back.

Researchers measured testosterone levels by taking saliva samples from 600 childless men in the Philippines, then repeated those tests for five years. The men who had kids during that time saw their levels plunge by 50 percent in the first month of fatherhood.

Those who were most involved in physically caring for their child had the biggest drops. (If you ever needed an excuse to skip diaper-change, this is it!)

Testosterone levels eventually recovered when the children reached toddlerhood — but not completely. Men with kids had 34 percent less testosterone by the end of the study, while men without had drops of just 14 percent (we all lose a little as we age).

But you don't have to tolerate low testosterone levels, whether you're a dad or not. There are simple steps you can take right now to keep your hormone levels exactly where they need to be.

First, be sure to get your rest. Testosterone levels can fall by 15 percent after just one week of sleepless nights, according to a recent study.

Next, lose some weight: Studies have found that overweight and obese men have lower levels of the hormone -- and that those levels rise when the weight comes off.

Finally, find a safe way to get off the drugs you don't need (and that's nearly all of them). Many come with side effects that are downright emasculating. One recent study found that men who take statins, for example, have double the risk of low testosterone.

If none of these apply to you, and you're suffering from low testosterone, here's one for you: Emerging research has found that an extract of the spice fenugreek can actually cause free testosterone levels to surge by as much as 96 percent. Read more about it here.

That's enough to turn you into the manliest dad -- or even granddad -- around.