The early postnatal period, mini-puberty, provides a window on the role of testosterone in human neurobehavioural development.

Experimental research in non-human mammals indicates that testosterone exposure during early periods of rapid brain development has enduring influences on brain and behaviour. These influences are exerted when testosterone is higher in developing males than females, and the affected characteristics are those that differ by sex. Testosterone is higher in males than in females from about weeks 8 to 24 of human gestation and then again during early infancy, and both of these periods are times of rapid brain development.

Early postnatal testosterone predicts sex-related differences in early expressive vocabulary.

During the first few years of life, girls typically have a larger expressive vocabulary than boys. This sex difference is important since a small vocabulary may predict subsequent language difficulties, which are more prevalent in boys than girls. The masculinizing effects of early androgen exposure on neurobehavioral development are well-documented in nonhuman mammals.

No relationship between early postnatal testosterone concentrations and autistic traits in 18 to 30-month-old children.

Background: Some previous research has suggested that testosterone prenatally contributes to gender differences in autistic traits, but little is known about the role of testosterone during early postnatal development (mini-puberty). Two prior studies found no sex difference in testosterone postnatally in saliva samples and detected little to no relationship between testosterone postnatally and autistic traits in toddlers. These findings may reflect late measurements of testosterone at 3 to 4 months of age, after the peak of mini-puberty at 1 to 3 months of age.