Health Questions and Answers

Question: Does puberty simply represent the final, complete development of the hypothalamic-pituitary-gonadal (HPG) axis?


No.  It appears that the HPG axis is intact as early as 20 weeks of life. Pituitary gonadotrophs have been found to produce LH and FSH at this gestational age, and in boys testicular testosterone is essential for normal internal and external genital development. In female fetuses, functional ovarian cysts are occasionally seen. These findings indicate a functional HPG axis in fetal life. LH and FSH levels peak at 20 weeks of gestation and then are suppressed by maternal estrogen. Immediately postpartum, LH and FSH levels flare for 1-2 years and then are suppressed until puberty either by exquisite sensitivity to very low levels of estrogen or by a central inhibiting factor.


  • Reindollar RH, Byrd JR, McDonough PG: Delayed sexual development: A study of 252 patients. Am J Obstet Gynecol 140:371, 1981. Medline Similar articles
  • Marshall WA, Tanner JM: Variations in pattern of pubertal changes in girls. Arch Dis Child 44:291, 1969. Medline Similar articles
  • Mishell DR, Stenchever MA, Droegenmueller W, Herbst AL (eds): Comprehensive Gynecology, 3rd ed. St. Louis, Mosby, 1997.

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