gynecology and obstetrics
Female Reproductive Endocrinology
Puberty
Puberty is the sequence of events in which a child acquires adult physical characteristics and capacity for reproduction. Circulating LH and FSH levels are elevated at birth but fall to low levels within a few months and remain low until puberty. Until puberty, few changes occur in reproductive target organs. The age of onset of puberty and the rate of development through different stages are influenced by different factors. Over the last 150 years, the age at which puberty begins has been decreasing, primarily because of improved health and nutrition, but this trend has stabilized. In the US the average age for onset of puberty is 12.5 years, but onset varies by ethnicity ( Puberty references ). Puberty often occurs earlier than average in moderately obese girls and later than average in severely underweight and undernourished girls ( Puberty references ). Such observations suggest that a critical body weight or amount of fat is necessary for puberty. Many other factors can influence when puberty begins and how rapidly it progresses. For example, there is some evidence that intrauterine growth restriction, especially when followed by postnatal overfeeding, may contribute to earlier and more rapid development of puberty ( Puberty references ). For example, some evidence suggests that children born small for gestational age have a more advanced progression of puberty ( Puberty occurs earlier in girls whose mothers had an earlier age at menarche ( Puberty references ); puberty is also influenced by geographic location and environmental toxicants ( Physical changes of puberty occur sequentially during adolescence (see figure Puberty—when female sexual characteristics develop ). [ Puberty references ]) and onset of the growth spurt are usually the first changes recognized. Then, pubic and axillary hair appear (see figure Diagrammatic representation of Tanner stages I to V for development of pubic hair in girls ), and the growth spurt peaks. Menarche (the first menstrual period) occurs about 2 to 3 years after breast budding. Menstrual cycles are usually irregular after menarche and can take up to 5 years to become regular. The growth spurt is limited after menarche. Body habitus changes and the pelvis and hips widen. Body fat increases and accumulates in the hips and thighs. Mechanisms initiating puberty are unclear. Central influences that regulate release of GnRH include neurotransmitters and peptides (eg, gamma-aminobutyric acid [GABA], kisspeptin). Such factors may inhibit release of GnRH during childhood, then initiate its release to induce puberty in early adolescence. Early in puberty, hypothalamic GnRH release becomes less sensitive to inhibition byestrogenandprogesterone. The resulting increased release of GnRH promotes LH and FSH secretion, which stimulates production of sex hormones, primarilyestrogen.Estrogenstimulates development of secondary sexual characteristics. Pubic and axillary hair growth is stimulated by the adrenal androgens dehydroepiandrosterone (DHEA) and DHEA sulfate; production of these androgens increases several years before puberty in a process called adrenarche. Bars indicate normal ranges. From Marshall WA, Tanner JM: Variations in pattern of pubertal changes in girls.Arch Dis Child44:291–303, 1969; used with permission. From Marshall WA, Tanner JM: Variations in patterns of pubertal changes in girls.Archives of Disease in Childhood44:291–303, 1969; used with permission. 1.Anderson SE, Must A: Interpreting the continued decline in the average age at menarche: results from two nationally representative surveys of U.S. girls studied 10 years apart.J Pediatr147 (6):753–60 2005.doi: 10.1016/j.jpeds.2005.07.016 2.Rosenfield RL, Lipton RB, Drum ML: Thelarche, pubarche, and menarche attainment in children with normal and elevated body mass index.Pediatrics123 (1):84-8, 2009. doi: 10.1542/peds.2008-0146 3.Darendeliler F: IUGR: Genetic influences, metabolic problems, environmental associations/triggers, current and future management.Best Pract Res Clin Endocrinol Metab33 (3):101260, 2019. doi: 10.1016/j.beem.2019.01.001 Epub 2019 Jan 22. 4.Veening MA, van Weissenbruch MM, Roord JJ, de Delmemarre-van Waal HA: Pubertal development in children born small for gestational age.J Pediatr Endocrinol Metab17 (11):1497–505, 2004. doi: 10.1515/jpem.2004.17.11.1497 5.Sørensen S, Brix N, Ernst A, et al: Maternal age at menarche and pubertal development in sons and daughters: A Nationwide Cohort Study.Hum Reprod33 (11):2043–2050, 2018. doi: 10.1093/humrep/dey287 6.Eckert-Lind C, Busch AS, Petersen JH, et al: Worldwide secular trends in age at pubertal onset assessed by breast development among girls: A systematic review and meta-analysis. JAMA Pediatr174 (4):e195881, 2020. doi:10.1001/jamapediatrics.2019.5881 7.Marshall WA, Tanner JM: Variations in patterns of pubertal changes in girls.Arch Dis Child44:291–303, 1969. 