If you had no idea that changes in season coincided with alterations in blood testosterone concentrations, join the crowd. A recent report in the Journal of Clinical Endocrinology and Metabolism1 looked at total and free testosterone, LH (luteinizing hormone— a brain hormone that stimulates the testes to secrete testosterone) and SHBG (sex hormone binding globulin— a protein that binds to testosterone, dihydrotestosterone and estradiol and serves to carry it through your circulation; changes in its concentration significantly affect the ratio of unbound [biologically active] testosterone to estradiol in plasma) in a group of 1,549 men living in Norway. (I didn’t know there were that many people in Norway). 

What they found was intriguing. Total testosterone (T) peaked in the months of October and November, with a smaller peak in February. June levels of total T were the lowest. Moreover, free T peaked in December and reached a low point in August. The subjects’ waist-to-hip ratio followed the pattern for T.  That is, they were highest when T was lowest. So, subjects were perhaps leaner during the cold winter months, which, by the way, also have the fewest hours of sunlight. Furthermore, the variations in hormone levels were quite large (31 percent difference between peaks and nadirs). So what the hell does this mean? Should you move to Canada and go ice fishing after a heavy session of back and biceps? 

Maybe all those people living in Southern California would be better off if they headed for the Aleutian Islands. On the other hand, it could be an evolutionary adaptation for people who live in areas with extreme changes in weather (i.e., very bitter cold winters). The pattern in Norway, at least, is for T to be highest in the winter months. Let’s face it, the idea of sitting on your lawn chair chillin’ with your neighbors as you grill a big fat steak just doesn’t cut it, especially when it’s 10 degrees. So evolution has equipped man with jacked up T levels so that you are better prepared for those wonderful indoor activities with your wife or girlfriend named Greta. Hey, it’s a great way to pass time during those long winter months, eh?

Getting Old Bites
Seven healthy middle-aged men (47 years old) and six young men (24 years old) had levels of testosterone measured at night to see if there were age-related differences.2  In the young studs, the average hourly testosterone level at night was 60.6 nanograms per milliliter (ng/ml— integrated area under the curve) compared to 43.4 ng/ml in middle-aged men. LH values in the middle-aged men were higher than their young counterparts. Furthermore, young guys had an average of 6.7 testosterone pulses per night compared to 3.8 in the middle-aged guys. I guess if you’re young, enjoy your naturally high T levels. It certainly makes it easier for you to get home from an all-night jaunt at your local club with enough energy to romp around with that hot co-ed sporting a tattoo on her sacrum and strategic piercings throughout her anatomy. And the middle-aged guys? Well, they probably make more money. They may have to buy some extra T from their personal physicians. 

Good Steroid
DHEA is a steroid made in the adrenal glands; there’s some evidence that a dose of 50 to 100 milligrams per day might increase muscle mass and improve feelings of well-being in middle-aged to older individuals. Also, older men demonstrate improved immune function after five months of DHEA supplementation. Though originally touted as the “anti-obesity” steroid, it’s clear that in humans, it’s not an anti-obesity hormone. But DHEA does have some fascinating effects.3

For instance, work from Kumamoto University School of Medicine in Japan examined the effects of supplementing 25 milligrams per day (for 12 weeks) of DHEA on endothelial function, insulin sensitivity and fibrinolytic activity. The average age of these male subjects was 54. According to the researchers, “Low dose DHEA supplementation improves vascular endothelial function and insulin sensitivity.” This is further evidence that with age, it may behoove you middle-aged guys to contemplate steroid supplementation of some sort. An improvement in insulin sensitivity could translate into better body composition as well as general improvement in health. 

T Levels Help Brain Blood Flow
We know that low levels of serum T makes for a grumpy fellow. High levels of T, on the other hand, allow you to work out like the Tasmanian Devil, stay up all night chasing tail, and avoid asking for directions at all costs (kidding). It should not be lost on my fellow T fans that not only is it good for the brawn; it’s damn good for the noggin. Researchers at Loyola University, Chicago, studied cerebral perfusion (blood flow) in seven hypogonadal men on testosterone replacement therapy.4 They found that after three to five weeks of treatment, perfusion in the midbrain and superior frontal gyrus (a convolution, namely Brodman area 8) was enhanced. At 12-14 weeks, there was an enhancement in the midcingulate gyrus (Brodman area 24). According to these scientists, “This study provides objective evidence that testosterone and/or its metabolites increased cerebral perfusion in addition to the improvement in cognitive function.”  Now, that’s what I wanted to hear. The stuff makes ya smarter! 

Protein and Kidney Function
In individuals with moderate to severe renal insufficiency, low protein intake may ameliorate the decline in kidney function. A recent study determined whether protein intake influences the rate of renal function change in women over an 11-year period. A total of 1,624 women enrolled in the Nurses' Health Study (42 to 68 years of age) in 1989 and gave blood samples in 1989 and 2000.5 Protein intake was assessed via a food-frequency questionnaire. The researchers found that high protein intake didn’t affect kidney function in women with normal kidneys. However, high total protein intake, particularly high intake of non-dairy animal protein, might exacerbate renal function decline in women with mild renal insufficiency. This is fascinating in that the substitution of dairy protein for other animal sources might offset the decline seen in women with mild renal insufficiency. This points out, once again, that not all proteins are treated equally by your body. So, you can’t go wrong with milk, whey, or caseinate proteins!

References
1.  Svartberg J et al. Seasonal variation of testosterone and waist to hip ratio in men: The Tromso Study.  J Clin Endo Metab 88(7):3099-3104.
2.  Luboshitzky R et al. Middle-aged men secrete less testosterone at night than young healthy men. J Clin Endo Metab 88(7):3160-3166.
3.  Kawano H et al. Dehydroepiandrosterone supplementation improves endothelial function and insulin sensitivity in men.  J Clin Endo Metab 88(7):3190-3195.
4.  Azad N et al. Testosterone treatment enhances regional brain perfusion in hypogonadal men.  J Clin Endo Metab 88(7):3064-3068.
5.  Knight EL et al. The impact of protein intake on renal function decline in women with normal renal function or mild renal insufficiency. Ann Intern Med 138:I151, 2003.