The Endocrine Control of Puberty Introduction Physical and sexual changes that occur in adolescence Sudden increase in linear growth the pubertal growth spurt Pubertal Changes cid 127 Occurs approximately 2 years earlier in girls than in boys Age ranges are 7 13 and 9 15 in girls and boys respectively Best indicator is in girls onset of menarche Similar indicator in boys is spontaneous erection and maybe ejaculation during sleep Secondary sexual characteristics In females these are the breasts the pubic and axillary hair the widening of the hips and the distribution of fat In males they include the growth of the testis and penis pubic and axillary hair facial and body hair and greater muscle development The Tanner stages provide a useful guide to classify the normal sexual development of a boy or girl Stage 2 testes and scrotum enlarge the scrotum changes texture and reddens Stage 3 further enlargement of testes and scrotum penis lengthens Stage 4 further increase in penile length and circumference with the glans developing testes and scrotum continue to grow with the color of the Boys male genitalia Stage 1 prepubertal stage scrotum darkening Stage 5 adult genitalia cid 127 Girls breast development Stage 1 prepubertal stage Stage 2 breast bud with raised papilla and enlargement of areola Stage 3 further enlargement of breast and areola which remain together in contour Stage 4 areola and papilla separate from breast contour forming a secondary mound Stage 5 adult stage with projection of papilla only Boys and girls pubic hair Stage 1 prepubertal stage any hair at this stage is similar to rest of abdominal hair Stage 2 sparse growth long straight or curled along the labia or around the base of the penis Stage 3 increased growth of coarser darker and curlier hair spreading in area but still relatively sparse cid 127 Girls enter the growth phase from a lower starting point and reach the stage where the epiphyses have fused earlier than boys resulting in shorter stature Development of abstract reasoning logical thought the appreciation of consequences the establishment of identity and relationship to and with others Stage 4 hair adult in type but still restricted in area Stage 5 adult in type and amount Physical growth The pubertal growth spurt starts approximately 2 years earlier in girls than in boys In girls final height is attained at 15 16 years and in boys at 17 18 years Body weight also increases during puberty cid 127 Mental changes Acceptance of increased autonomy and responsibility cid 127 Often a period of experimentation Increased intensity of mood states Changes associated with brain growth and endocrine changes Adrenarche 2 years before the onset of puberty there is a sudden increase in weak androgen production by the adrenal glands Stimulus is unknown but reaching a certain body weight may be a key factor cid 127 Only known effect of the increase in circulating DHEAs is the initial production of axillary and pubic hair the development of apocrine glands in the skin and Consequences body odor and increased production of sebum may cause acne The endocrine basis for the pubertal changes sweat secretion steroids Basal levels of various metabolic hormones are necessary together with the determining feature of the onset of increased production of GH and the gonadal cid 127 Gonadal steroid production is regulated mainly by LH and FSH cid 127 GnRH mainly regulates LH and FSH release and GHRH and somatostatin regulate GH release What is the signal for the onset of puberty over the past 20 30 years Population studies indicate that the body weight at which puberty begins has remained constant 47 5 kg in girls Linked to the switching on of hypothalamic GnRH neurons by factors associated with the metabolic status of the child cid 127 Over the past 170 years or so the age at which puberty occurs marker menarche has decreased from approximately 16 down to 10 years leveling out cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 The regulation of GnRH neurons appetite stage Located particularly in the medial basal hypothalamus an area which includes the arcuate nucleus key area involved in the regulation of feeding and Stimulatory fibers include neurons releasing glutamate while inhibitory fibers include those releasing GABA and neuropeptide Y Nearby neurons which release naturally occurring opioids such as enkephalin may also be inhibitory on the glutamatergic neurons during the prepubertal In addition to hormones such as IGF 1 iodothyronines and the gonadal steroids themselves one likely factor may well be leptin Concentration in the plasma increases in direct proportion to amount of body fat Ideal intermediate between nutritional status and puberty trigger GnRH neurons The Kiss gene and its products Kisspeptin is a ligand for an originally identified orphan G protein coupled receptor called GPR54 Both the KiSS 1 gene and GPR54 are located in the medial basal hypothalamus Inactivating mutations in the GPR54 gene are associated with hypogonadotrophic hypogonadism and absent puberty while activating mutations cause precocious puberty Puberty is associated with increased KiSS 1 expression suggesting that kisspeptin is stimulating the GnRH neurons via the GPR54 receptor cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127 cid 127