The timing of adrenarche in Maya girls, Merida, Mexico

In this pilot study we investigated age at adrenarche and body composition among 25 urban Maya girls aged 7-9 living in low-income, urban households in Merida, Mexico. Adrenarche involves the maturation of the hypothalamic-pituitary-adrenal axis and increased production of the adrenal androgens dehydroepiandosterone (DHEA) and its sulfate ester (DHEA-S). It occurs around age 6-8 in contemporary, industrialised populations among whom adrenarche has been studied from a primarily clinical perspective and, developmentally, marks the transition 2 from childhood to juvenility. The few available studies of adrenarche in subsistence level populations, however, indicate a later age (8-9) than suggested by industrialized groups. It is linked to the appearance of some secondary sexual characteristics and some studies associated it with body composition, particularly, the timing of the BMI (what others term adiposity) rebound. Since the urban Maya in Merida are undergoing a nutritional transition and increases in overweight/obesity, we hypothesized that adrenarche -- assessed using salivary levels of DHEA-S -- would occur earlier among Maya girls. The hypothesis was rejected since adrenarche occurred later than expected at close to 9 years. Nevertheless, overweight or obese girls were more likely to have undergone adrenarche, whereas pre-adrenarcheal girls were smaller and thinner. Further studies and larger sample sizes are required to illuminate how adrenarcheal variation relates to body composition, pubertal progression and developmental plasticity in other non-Western populations.