"Men are so grumpy," stated a twice divorced lady friend in a wide-ranging telephone conversation that included the subject of relationships the other day.

My response to the unexpected remark was a rather foolish "Well, I have no idea what makes them that way." You say the dumbest things sometimes when you are taken by surprise and don't know what else to say. 

Perhaps a generalization in my friend's case, but nonetheless not without merit. No doubt she knew all to well whereof she spoke.

In retrospect, being a man myself and collectively guilty as charged, I have a pretty good idea of what contributes to grumpiness in men and I have been compelled to not dismiss my lady friend's comment quite so lightly.

Recent research tells us that most men suffer from 'Grumpy Old Man' syndrome when they hit 70. There are good reasons to believe this to be the case. Seventy is an age when men may become more aware of their own mortality as they see friends and loved ones pass on. They might be struggling with wearisome health problems, and/or feel depressed because they have no aspirations or goals left to attain. 'Grumpy Old Man' syndrome is also and most likely due to the fact that testosterone levels in a 70-year-old are quite probably half the normal levels of a younger man.

Whereas women's estrogen levels drop relatively suddenly when they go through menopause, causing a variety of noticeable symptoms, men's testosterone levels drop gradually over a period of time so the symptoms are not as obvious.

From experience, and not to make excuses, there is a good possibility that men who suffer from this syndrome may experience a sense of feeling burned out, increased depression, increased irritability, increased anxiety, more nervousness, more bodily complaints, reduced mental effectiveness and increased sweating (even hot sweats). They may have a need for more sleep or suffer sleep disturbances. It goes without saying that muscular weakness, physical exhaustion, impaired sexual potency and disturbed libido also have a way of eating away at a man's ego. 

Frankly, it's enough to drive any guy around the bend.

I'm told that stress, toxicity, a poor diet with too many bad fats, autoimmune diseases and some drugs can also lead to a drop in testosterone levels. Likewise, abdominal fat, which makes estrogen, will neutralize the testosterone and cause levels to drop further.

And finally, there is the fact that the world is changing around us, and rarely to our high standards. Aging men, in particular, succumb to the nearly irresistible temptation to look at The World These Days and find it hopelessly screwed up. The tendency, unfortunately, is to take it out on those the closest to us.

With all of this evidence of decline, how can we not be grumpy?

Author Michael Gurian has spent a lifetime studying and writing about our journeys through life -- often with an emphasis on male psychology. His most recent book, “The Wonder of Aging: A New Approach to Embracing Life After Fifty” addresses how men and women age differently – and why men sometimes turn sour.

First of all, Gurian confirms that low testosterone can, in fact, be one of the culprits. Starting at about the mid-40s or 50s, every man’s testosterone levels begin to decrease, and sometimes the decrease is precipitous around age 60.

“The whole system is robbed of a chemical that it based its life on for the first 50 years,” said Gurian. “It can create irritability. And a lot of us get kind of depressed. Females can get immensely irritated, too. But when they are depressed, they evidence it in crying and talking about how they feel. Males tend to use anger more.”

Or to put it another way: Women fret, men yell.

So, are those ubiquitous testosterone supplements the solution? Nope. It’s not that easy. First, as the Mayo Clinic notes, “whether treatment is necessary is a matter of debate.” Second, there are many, many other reasons why men get grumpy.

Some have been physically active but when they put on weight and don’t exercise they tend to be more irritable with age, probably because they have more to be irritated about. They lose even more of their athletic identity or youthful vigor.

It’s really a rite of passage, where the body changes and you can’t do what you used to do, the mind being willing but the body not so much.

There is something debilitating about not being able to cut the mustard any more -- and worrying about it.

This is not just about sports and other declining physical attributes. Some guys lose something they feel is even more vital -- which is why Viagra is such a big seller. Men use it to “put off that identity shift,” as Gurian puts it, into their older selves.

However, the deeper causes of Grumpy Old Man syndrome lie in the emotional and psychological realms. Men go through divorces. They retire and lose their workplace identity.

“With anything that’s really tough, guys will tend to ‘fight or flight,’ ” said Gurian, who is also a marriage and family counselor. “Some of the fight stuff is anger. Some of the flight stuff is withdrawal.”

That’s partly why men experience more quick bursts of anger in their 50s and 60s. There’s “nothing inherently wrong with male anger,” Gurian said. However, if your “quick bursts” go from once a week to a few times every day? Well, now you’re entering full-blown Guy Who Gets Irritated by Everything territory.

Now that we know a little more about the causes, the question remains: How can we avoid turning into Grumpy Old Men?

The key, according to Gurian, is making a true identity shift. Between the ages of 50 and 65, every man needs to “let go of lost youth.” Our youth really is gone and not coming back. We all need to create new, more age-appropriate identities for ourselves.

The important thing is to shift your energy into something. Maybe you can coach the sport you love. Maybe you can turn to golf, a sport easier on the tendons. But don’t just sit on the couch and do nothing.

Similar shifts may have to take place when it comes to relationships, or sex, or your spiritual life. Every man needs to make these kinds of shifts between the ages of 50 and 65. The process described by Gurian makes absolute sense. You must stop clinging to your youthful self, and accept your new, older self. It all boils down to an old-fashioned, yet wise concept: aging gracefully.

So here’s the secret to not turning into a Grumpy Old Man: Shift still not-inconsiderable energies into new, constructive pursuits -- ones that make sense for a 60+-year-old man. 

Most of all fellows, don't let "grumpy" define you! It can ruin being around an otherwise pretty good guy.