Salivary testosterone levels among Tamang and Kami males of central Nepal

Abstract

Salivary testosterone levels are reported for 65 Nepalese males between the ages of 15 and 48 years who were drawn from 2 different ethnic populations (Tamang and Kami) from the central highlands of Nepal. Subjects collected morning and evening saliva samples on five consecutive days in two contrasting seasons, the winter dry season and the summer monsoon season. Anthropometric indexes of acute and chronic nutritional status were also measured. Morning and evening salivary testosterone levels in the winter averaged 233 +/- 14 (SE) pmol/L and 166 +/- 8 pmol/L, respectively, for the Tamang and 249 +/- 14 pmol/L and 163 +/- 13 pmol/L, respectively, for the Kami. In the summer the corresponding values were 219 +/- 12 pmol/L and 156 +/- 8 pmol/L for the Tamang and 249 +/- 19 pmol/L and 147 +/- 12 pmol/L for the Kami. These levels are significantly lower than those reported for Western populations and close to those reported for other non-Western populations. The magnitude of diurnal variation in salivary testosterone levels and the absence of significant age variation are also comparable with observations made on other populations. Weak relationships were observed between testosterone levels and indexes of acute and chronic nutritional status in the winter only. The absence of pronounced variation in salivary testosterone levels between populations and the absence of strong associations between salivary testosterone levels and indexes of acute and chronic nutritional status contrast with the prominent ecological and interpopulation variation reported for salivary progesterone levels in women. Male gonadal function seems less sensitive to moderate energetic stress than female gonadal function, probably reflecting the fact that energy availability is less crucial to male reproductive success than to female reproductive success. Variation in testosterone level associated with chronic energetic stress may be an adaptive somatic response to avoid the maintenance costs of a large active metabolic mass with little direct impact on male fecundity.