Pubertal timing, hormones, and body composition among adolescent Turkana males

Abstract

The Turkana, like other East African pastoral groups, are known for their tall adult stature, achieved despite a blunted growth spurt during adolescence and continued growth into the early 20s. To investigate the hormonal mechanisms associated with the pattern of slow and continued adolescent growth, we collected data on hormonal status, height, weight, and trunk skinfolds and ethnographic self-reports of testicular maturation in a cross-sectional sample of 35 nomadic and 37 settled Turkana males aged 14-24. Hormonal determinations included testosterone (T), sex hormone-binding globulin (SHBG), and dehydroepiandrosterone (DHEA) in blood, in addition to urinary DHEA. Self-reports of testicular maturation showed no difference between settled and nomadic subpopulations. However, nomadic boys exhibited significantly higher levels of T, DHEA, and SHBG. Of all the hormones, only SHBG showed a significant relationship with age. Multiple regression models show blood T and SHBG to be significant independent predictors of achieved height as well as weight, controlling for age. Our results suggest that onset of puberty is substantially delayed among Turkana males, and that bioavailable T is related to growth in stature during adolescence. We suggest that SHBG acts to mediate the effects of energy availability on adolescent growth in this energetically limited population. Our findings may also have implications for understanding adolescent growth among Homo erectus.

Fat and muscle mass in different groups of pre-pubertal and pubertal rural children. Cross-cultural comparisons between Sahelian (rural Senegal) and Amazonian (Beni River, Bolivia) children

“…Boys also presented very slow growth during pubescence (Benefice 2007). A similar late onset of puberty was observed in other African groups, including the Turkana and Karamajong of Eastern Africa (Campbell et al 2005,Gray et al 2004). …”

“…A G2 stage of around 9.2 to 10.03 was observed in the NHANES III study (Sun et al 2002). This delay in puberty onset is concomitant with a very low level of blood testosterone (Campbell et al 2005). In girls, age at first menstruation was estimated by Sandra Gray to be 16.5 years.…”

“…A recent paper confirms that adolescent Turkana boys presented a considerable delay in puberty. Enlargement of testicular volume was first noted at 16.0 ± 1.9 years (Campbell et al 2005). This would correspond to the G2 stage of Tanner (Tanner 1962).…”

Impacts of dietary intake and helminth infection on diversity in growth among schoolchildren in rural south China: A four‐year longitudinal study

“…Sensitivity to such environmental stresses is higher in preadolescent ages than in adolescent or adult ages (Bogin, 1999;Frisancho et al, 1980;Johnston and Beller, 1976). Some studies have shown that delayed growth in preadolescence due to nutritional stress was followed by compensatory gain in adolescence (Kulin et al, 1982;Pawloski, 2003), while it has commonly been recognized that environmental stress such as helminth infection and malnutrition tends to reduce the maximal potential responses of bone, muscle, and fat tissues to hormonal function that determines adolescent growth, thereby hampering the compensatory gain (Cameron et al, 1993;Campbell et al, 2005;McGarvey et al, 1992).…”

Human Reproductive Ecology

“…In part because of the lack of a visible marker of puberty such as menarche, studies of the population variation in age at puberty of boys are much more limited than those for girls (Zemel et al, 1993;Panter-Brick et al, 1996;Campbell et al, 2004). Energy deficiency has been associated with later ages at puberty in Kenyan and Zambian boys, as measured by pubertal hormone changes (Campbell et al, 2005). Energy deficiency has been associated with later ages at puberty in Kenyan and Zambian boys, as measured by pubertal hormone changes (Campbell et al, 2005).…”