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4 - Normal childhood, puberty and adolescence
- from Part I - Normal development
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- By Clementina La Rosa, Department of Paediatric Endocrinology, Great Ormond Street Hospital for Children and The Middlesex Hospital, London, UK, Cristina Traggiai, Department of Paediatric Endocrinology, Great Ormond Street Hospital for Children and The Middlesex Hospital, London, UK, Richard Stanhope, Department of Paediatric Endocrinology, Great Ormond Street Hospital for Children and The Middlesex Hospital, London, UK
- Edited by Adam H. Balen, Sarah M. Creighton, Melanie C. Davies, University College London, Jane MacDougall, Richard Stanhope
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- Book:
- Paediatric and Adolescent Gynaecology
- Published online:
- 04 May 2010
- Print publication:
- 01 April 2004, pp 44-50
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- Chapter
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Summary
Introduction
Sex determination, or genetic sex, is a process starting at conception by which the undifferentiated genitalia evolve into male or female reproductive organs. It depends on chromosomal complement and is influenced by endocrine events and by nongenetic and nonendocrine factors such as nutrition, toxins (fetal alcohol syndrome), intrauterine environment (altered uterine blood flow, placental function, local uterine circulation and placental and umbilical circulation).
Initially this cascade of events is dependent on chromosomal or genetic sex, and then appropriate development of the hypothalamic—pituitary—gonadal axis is necessary for sex steroid secretion as well as for oogenesis and ovulation in the female and spermatogenesis in the male.
Genotype and phenotype
Genetic sex directs the embryonic gonad to differentiate into either testis or ovary and is determined by the presence or the absence of the Y chromosome.
The sex-determining region of the Y chromosome (SRY) has been mapped to the tip of the Y chromosome (Parker et al., 1999) and has been shown to be necessary and sufficient to initiate the male differentiation pathway and acts as a genetic switch towards testis development. If it is absent (or delayed in expression), ovarian differentiation occurs. However, many other factors involved in sex differentiation have been identified and are located on autosomal genes. In the presence of “male differentiating signals”, testosterone and Müllerian inhibiting factor (anti-Müllerian hormone (AMH) or Müllerian inhibiting substance) are secreted by the fetal gonads. Testosterone is converted to dihydrotestosterone by the 5α-reductase enzyme in target tissues.
18 - Disorders of growth and puberty
- from Part III - Management of specific disorders
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- By Cristina Traggiai, Department of Paediatric Endocrinology, Great Ormond Street Hospital for Children and The Middlesex Hospital, London, UK
- Edited by Adam H. Balen, Sarah M. Creighton, Melanie C. Davies, University College London, Jane MacDougall, Richard Stanhope
-
- Book:
- Paediatric and Adolescent Gynaecology
- Published online:
- 04 May 2010
- Print publication:
- 01 April 2004, pp 231-241
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- Chapter
- Export citation
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Summary
Introduction
Puberty is defined as the acquisition of secondary sexual characteristics associated with a growth spurt and resulting in the attainment of reproductive function. The endocrine events of puberty commence many years before the onset of phenotypic puberty (see Ch. 4). The onset of puberty is characterized by nocturnal luteinizing hormone (LH) release. It is a result both of increased pituitary sensitivity to gonadotrophin-releasing hormone (GnRH) caused by prolonged unopposed oestrogen exposure of the gonadotrophic cells and of gonadal hormone secretion. In boys, spermatogenesis is initiated at stage 3, and menarche in girls occurs during late puberty. Initial menstrual cycles are usually anovulatory, which is associated with irregular and often painful periods. Precocious puberty is defined as the development of sexual characteristics before the age of eight years in girls and nine years in boys. Delayed puberty is defined when there is no sign of puberty at the age of 13.4 years in girls and 14 years in boys (2SD above the mean of chronological age for the onset of puberty).
It is important to recognize the harmony of normal events (consonance) of puberty; when it is absent, an endocrine disorder should be suspected. The loss of consonance has been described as one of the first signs of an endocrine disease (e.g. hypothyroidism, Cushing's syndrome, gonadal dysgenesis), in the absence of more obvious manifestations (Stanhope et al., 1986).
Disorders of pubertal development
The classification of disorders of pubertal development are described in Table 18.1.