Decoding Mini-Puberty and Its Clinical Significance: A Narrative Review

Mini-puberty refers to the transient activation of the hypothalamic-pituitary-gonadal (HPG) axis during early infancy, lasting up to six months in boys and 12-24 months in girls. This phase represents the second activation of the HPG axis, following its initial activation during the second half of fetal life. At birth, the removal of the suppressive effect of placental estrogens on the HPG axis prompts a rise in both gonadotropins and sex steroid hormones, resulting in distinct clinical and laboratory markers of mini-puberty. While the clinical significance of mini-puberty remains partially understood, emerging evidence underscores its essential role in several aspects of human growth and development. In boys, testosterone influences penile growth, increases Sertoli cell numbers in the testes, and lays the foundation for future spermatogenesis. In girls, the increase in estradiol levels promote follicular maturation and stimulate breast and uterine growth. Beyond the gonadal effects, mini-puberty appears to impact body composition, affecting body weight and promoting accelerated growth. Additionally, it may affect early psychosomatic and neural maturation, playing a role in several key aspects of the infantile brain. This narrative review examines recent findings on the physiology of the activation of HPG axis before and after birth along with its significance in various aspects of human growth and development. In addition, mini-puberty unique features in specific groups, such as preterm and small-for-gestational-age infants are presented.