Pubertal endocrinology of yellow baboon (Papio cynocephalus): Plasma testosterone, testis size, body weight, and crown‐rump length in males

Abstract

A cross-sectional study (n = 99) was made of male baboons (Papio cynocephalus) aged 3 weeks to > 10 years. Serum testosterone and testicular size were compared with body weight and crown-rump length. Pubertal onset in baboons occurs at 3-4 years of age; data were analyzed, therefore in three groups: 0-3 years; 3-4 years; and greater than 4 years. Testicular volume index increased minimally prior to 3 years of age. Between 3 and 4 years of age, there was a n increase (P < .05) in testicular growth, which was followed after 4 years of age by a return to the prepubertal rate. Plasma testosterone decreased from birth to 3 years of age. Between 3 and 4 years of age, there was an increase (P < .05) in testosterone. The levels of which remained unchanged after 4 years of age. A linear increase in body weight was observed for the first 3 years which was followed by an increase (P < -05) in the rate of weight gain between 3 and 4 years of age. After 4 years of age, body weight continued to increase but at a rate less than those of the two earlier periods. A linear increase in crown-rump length was observed over the first 3 years. Between 3 and 4 years of age there was a slight increase (P > .06) in crown-rump length, which approached zero after 4 years of age. These data demonstrate many similarities between the pubertal development of male baboons and humans. Male baboons appear to be appropriate for the study of reproductive and endocrine development and the factors involved in the pubertal growth spurt of the human male.

Coming of age: steroid hormones of wild immature baboons (Papio cynocephalus)

“…Consequently, comparisons among studies are of necessity presently limited. Nonetheless, the increase in fT concentration at the average age of testicular enlargement observed at Amboseli is in general agreement with previous studies of captive baboons [Castracane et al, 1986;Crawford et al, 1997;Muehlenbein et al, 2001], which all found an increase in plasma T concentrations around the time of testicular enlargement. In our analysis of the 1.5 years preceding maturation, we found a near significant (P=0.053) fT increase in the 6 months preceding maturation.…”

“…While menarche is used as an obvious criterion for sexual maturity in females of many primate species, for males there is no obvious or standardized marker to indicate sexual maturity. In the primate literature, the onset of puberty or sexual maturation is reported as the time of testicular descent (e.g., macaques) or enlargement (e.g., humans and baboons), depending on whether the species has testes that are scrotal or inguinal at birth [Castracane et al, 1986;Crawford et al, 1997;Ginther et al, 2002;Muehlenbein et al, 2001Muehlenbein et al, , 2002Nieuwenhuijsen et al, 1987;Nottelmann et al, 1987]. However, both testicular enlargement and descent occur in a gradual fashion.…”

“…Most of the literature on steroid hormone variation during the juvenile period is derived from studies conducted on children [e.g., Angsusingha et al, 1974;Apter, 1980;Elmlinger et al, 2002;Genazzani et al, 1978;Sizonenko, 1989], and several key investigations of captive primates (e.g., baboons [Castracane et al, 1986;Crawford et al, 1997;Muehlenbein et al, 2001], rhesus macaques [Goy et al, 1982;Muehlenbein et al, 2002], and cotton-top tamarins [Ginther et al, 2002]). Large gaps exist in the available literature, and normative data from natural primate populations are virtually absent.…”

Preparation and activation: determinants of age at reproductive maturity in male baboons

“…Puberty in male primates is signalled by enlargement of the testes, which coincides with the production of viable sperm (Plant 1988;Castracane et al 1986;Bronson 1989;Bercovitch and Goy 1990). However, while pubescent male primates are physically capable of fathering offspring (van Wagenen and Catchpole 1956;Erwin and Mitchell 1975;Foerg 1982), this reproductive potential is not realized during the protracted adolescent period, during which males in natural social groups are reproductively inactive.…”

Measuring fecal testosterone in females and fecal estrogens in males: Comparison of RIA and LC/MS/MS methods for wild baboons (Papio cynocephalus)

“…When determined by RIA, fT concentrations in females were higher than in males, while the reverse pattern has been observed in yellow baboon serum (Castracane et al, 1986; Castracane and Goldzieher, 1983). Other studies have reported similar data to ours for fecal metabolites of T, and the authors of these other studies have suggested that these elevated fT concentrations in females were the result of cross-reaction of the antibody with hormone metabolites of different origins, such as DHEA, which is of adrenal origin (Dittami et al, 2008; Goymann, 2005; Hauser et al 2011; Möhle et al, 2002; Preis et al, 2011).…”