Within the first few months of life, the human infant experiences a transient activation of the hypothalamo-pituitary-gonadal axis. First described in the 1970s, after the development of assay methodology sufficiently sensitive to detect low levels of hormones in blood,1 this process has been described as a “mini-puberty.” Its purpose remains unclear, but is most commonly thought to be an important developmental event related to subsequent reproductive function.2,3 Mini-puberty occurs in both sexes, with an increase in testosterone in boys and increase in both estradiol and testosterone in girls (testosterone concentrations in girls are ∼30% lower than those in boys at peak). Resultant effects on the reproductive organs include testicular, penile, and prostate growth in boys, uterine and breast enlargement in girls, and sebaceous gland and acne development in both sexes. Effects of this early activation of the hypothalamo-pituitary-gonadal axis are not confined to the reproductive organs,...
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