Testosterone levels in saliva correlate well with serum testosterone levels [1, 2]. Studies show:
"among nomadic and settled Ariaal pastoralists of northern Kenya [. . .] salivary testosterone (T) levels (avg. am value = 176.8 +/- 74.8 pmol/l) were low compared to values from Western populations" [3]. A later study reports even lower levels among the Ariaal [4].
"in Harare, Zimbabwe [. . .] salivary T levels (AM = 196 +/- 96 pmol/l; pm = 172 +/- 98 pmol/l) were much lower [compared to 'Western populations']" [5].
Among men aged 15 to <30 years, mean salivary T for an American sample from Massachusetts is 335 pmol/l, compared to 286 pmol/l for the Congo sample [6].
[1] J Clin Endocrinol Metab. 1981 Nov;53(5):1021-4. Salivary testosterone in men: further evidence of a direct correlation with free serum testosterone. Wang C, Plymate S, Nieschlag E, Paulse
[2] Clin Chim Acta. 1987 Mar 30;163(3):309-18. Direct assay for testosterone in saliva: relationship with a direct serum free testosterone assay. Johnson SG, Joplin GF, Burrin JM.
[3] Am J Hum Biol. 2003 Sep-Oct;15(5):697-708. Salivary testosterone and body composition among Ariaal males. Campbell B, O'Rourke MT, Lipson SF.
[4] Aging Clin Exp Res. 2006 Dec;18(6):470-6. Age-related patterns of body composition and salivary testosterone among Ariaal men of Northern Kenya. Campbell BC, Gray PB, Ellison PT.
[5] Am J Hum Biol. 2004 Nov-Dec;16(6):704-12. Testosterone, aging, and body composition in men from Harare, Zimbabwe. Lukas WD, Campbell BC, Ellison PT.
[6] Hum Reprod. 2002 Dec;17(12):3251-3. Population variation in age-related decline in male salivary testosterone. Ellison PT, Bribiescas RG, Bentley GR, Campbell BC, Lipson SF, Panter-Brick C, Hill K.
I wonder if the low African T-levels are related to diet.
ReplyDeleteDiet and any number of other environmental factors affect testosterone levels. (Incidentally, that's one reason that even if black Americans were consistently shown to have elevated T levels -- and they're not -- I would hesitate to read any deep evolutionary meaning into that fact.)
ReplyDeleteThe point is whatever the reasons may be Europeans and Americans have higher T than black Africans. Wherever black Africans are different from whites and grossly similar to black Americans, we can't blame differences in circulating T.
Nomadic african male populations have blood testosterone level significantly above average western. This was the only study I found on testosterone blood (not salivary testosterone):
ReplyDeletehttp://onlinelibrary.wiley.com/doi/10.1002/ajhb.20468/abstract
Mean level of young western males is about 20 nmol/l.
Although the salivary and blood testosterone was correlated in Western populations, one can not exclude the possibility that the nomadic salivary testosterone test does not represent their blood level of testosterone. Some studies show that salivary testosterone of young nomadic amerindian men is about 3 times lower than that of young japanese and westerners, but it is very unlikely that testosterone blood of them is 3 times lower, in which case they do not develop (or develop poorly) secondary sexual characteristics. Facts like the different oral hygiene could explain the differences between Western and salivary testosterone nomadic groups. Well, this is a hypothesis ...
An addition: I have the intuition that nomadic populations have high levels of serum testosterone, not because they are black, but because they are more physically active than the average westerner. Obesity among young virtually nonexistent.
ReplyDelete"Nomadic african male populations have blood testosterone level significantly above average western."
ReplyDeleteDo the authors themselves actually say that?
I don't have a copy of that paper. I do have "Pubertal timing, hormones, and body composition among adolescent Turkana males" by the same group:
Our findings suggest delayed onset of
testicular growth, low gonadal and adrenal hormone levels
relative to Western clinical standards, and a lack of a
sharply delineated age-related increase in testosterone
during adolescence. They also indicate important agerelated
changes in SHBG among the nomads, which may
play a role in growth. While the results must be considered
preliminary, given the relatively small sample size, they
suggest that the slow growth in stature and lean physique
of Turkana boys during adolescence may be related to
nutritional status through the peripheral metabolism of
testosterone.