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Details Title: Puberty Description: 4.24.07 Total Flash Cards: 84 Created: 04/28/2007 12:11:31	To study from this set of flash cards, or to create your own your own study flash cards, register HERE. If you are already a registered user, CLICK HERE.
Cards Term What is puberty? Definition physical and biochem changes associated with the activation of the HPGonadal axis--leading to adult reproductive function Term what are major hormonal players? Definition GgRH, FSH, and LH Term What is the shape of GnRH? Definition decapaptide Term What is the fuciton of GnRH? Definition Gonadotropin-releasing hormone (GnRH) Stimulates the synthesis and secretion of gonadotropins (FSH and LH) from gonadotrophs in anterior pituitary Term Embryology of GnRH? Definition Neural cells originate in the olfactory placode, migrate during embryogenesis to the medial basal hypothalamus where their terminals end in the median eminence Term Describe the male/female release of GnRH Definition GnRH neurons release the GnRH in pulses: Female: vary during the menstrual cycle follicular phase: 60-90 mins luteal phase: 100-216 mins vary in different physiologic and pathologic states Male: 90 – 120 mins Vary in magnitude Term Where does GnRH act? Definition GnRH acts on receptors on the gonadotrophs in the anterior pituitary half life 2-4 mins, rapidly degraded by proteases after secretion Term what happens with continious stimulation of GnRH? Definition continuous occupancy of the GnRH receptor results in desensitization to further GnRH action (ie down regulated the pituitary) Term How do other neurotransmitters affect GnRH? Definition Regulatory neurotransmitters and neuropeptides endogenous opioids suppress GnRH release (get thin on dope) leptin increases GnRH output neuropeptide Y suppresses GnRH release Term What do FSH, LH, TSH, hCG have in common? Definition Glycoprotein, 2 subunits ? common subunit (FSH, LH, TSH, hCG) ? subunit unique LH and hCG ?-subunit differ by 30 AA Term Who produces HCG? Definition the placenta Term Does LH have a long or short half life? Definition LH ?Short half life: reflects GnRH pulse activity Term What horomone reflects what GnRH is doing? Definition LH Term Where are FSH receptors in females? Definition on granulosa cells. Term what does FSH do in females? Definition Stimulates follicular development granulosa cells to synthesize and secrete estrogen stimulates granulosa cell replication and follicle growth Term Where are LH receptors in Females? Definition LH receptors on theca cells, peri-ovulatory granulosa cells, and luteinized granulosa cells Term What does LH do in females? Definition Stimulates ovulation Resumption of oocyte meiosis Luteinization of theca and granulosa cells Maintains function of corpus luteum Term Where does FSH bind in males? Definition Binds to seminiferous tubules in sertoli cells Term What does FSH do in males? Definition Role in spermatogenesis – optimal qualitative spermatogenesis in humans Term Where does LH bind in males, and what does it do? Definition Binds to Leydig cells Testosterone synthesis Term What type of steroid producing cells are found in ovaries? Definition Granulosa cells, and theca cells Term What do granulosa cells do? Definition Granulosa cells respond to FSH production of estrogen production of inhibin Term What do theca cells do? Definition Theca cells respond to LH produce androgens (androstenedione and testosterone) androgens are aromatized to form estrogens Term What are steroid producing cells in the testes? Definition Leydig Cells and sertoli cells Term What do Leydig cells do? Definition Leydig Cells Respond to LH Produce testosterone Term What do sertoli cells do? Definition Sertoli Cells Support germ cell development Produce tight junction for blood testes barrier Produce inhibin Term What are the steps towards creating estradiol from cholesterol? Definition chole--pregenolone-- progesterone---test which can go to DHT (via 5 alpha reductase) or to estradiol with aromatase Term Where is estradiol prooduced, and what are its 3 functions? Definition Produced by maturing follicle within ovary Maturation of secondary sexual characteristics Maturation of reproductive tract Regulatory function ?E: ?FSH, ?/? LH ?E: ? GnRH Term Where is proogesterone produced, and what does it do? Definition Produced by luteinized granulosa cells in corpus luteum in the ovary after ovulation Produces changes in the endometrium that facilitate implantation of embryo Essential for maintenance of pregnancy Regulatory function ?P: ? FSH & LH ?P: ? GnRH secretion Term Where is T produced, and what is T responsible for ? Definition Leydig cells Spermatogenesis Sexual differentiation – Wolffian Male body habitus, voice changes Regulatory function: ?T: ? LH ?T: ? GnRH Term How is DHT made, and what does it regulate? Definition Converted from testosterone by 5?-reductase External virilization during embryogenesis Prostate Male sex characteristics during puberty Spermatogenesis Term After birth, how you loose oocytes? Definition only though the process of follicular growth and atresia Term How is the rate of occyte atresia increased? Definition Genetic factors: 2 X chromosomes necessary Turner’s Syndrome, Premature Ovarian Failure Chemotherapy Radiation Autoimmune Term Is gonadal steroid production required for development of normal phenotype? Definition no Term What horomones affect the uterus? Definition Estrogen: proliferation of endometrium Progesterone: decidualization, implantation Term What do the Wolffian ducts become? Definition Wolffian ducts: Physically attached to the indifferent gonad Epididymis, vasa deferentia, seminal vesicles Term What does the urogenital sinus become? Definition Urogenital sinus: Prostate Prostatic urethra Term What does antimullarian horomone do? Definition Antimullerian hormone Glycoprotein product of embryonic testis Ipsilateral suppression of mullerian ducts Term What does T do? Definition Testosterone Stimulate wolffian ducts Precursor for DHT Term what does DHT do? Definition Dihydrotestosterone Male external genitalia Term What is involved in the maturation of sperm? Definition Maturation of sperm Motility Modification of structure Loss of spermatid cytoplasm Term when is there a peak of T in males? Definition 17-70 Term what happens during the neonatal period to gonadotrophin levles? Definition Gonadotropin levels high after birth, up to 2 years release of suppression from maternal E and P transient E, T secretion induced by high FSH/LH Term What happens to the ovary and testis during Neonat? Definition Ovary: 1 cm in diameter 250-350 mg weight follicular cysts may be present due to higher gonadotropin levels Testis: Prespermatogenic cells present Term What happens during childhood to the ovary and testes? Definition Ovary : Relatively quiescent Follicles grow at all times and frequently reach antral stage (2-15 mm) Full follicular development does not occur Testis : Quiescent Term During childhood, what happens to the pituitary and hypothal? Definition Pituitary & Hypothalamus FSH, LH, estradiol & testosterone levels suppressed low level pulses Central suppression of hypothalamus children with gonadal dysgenesis have FSH and LH levels similar to normal children GnRH will stimulate FSH and LH secretion in these agonadal children Term What happens with prepuberty? Definition Increase in FSH and LH pulse amplitude and frequency Initially LH pulse observed only at night Similar pulses of less amplitude occurring throughout the 24 hours In the adult pulses occur at set intervals Term Where is the LH pulse initially observed? Definition Initially LH pulse observed only at night Term What happens with LH during puberty in a female? Definition Normal adult LH pulse frequency and amplitude Gonadotropin secretion leads to estrogen production by the ovaries At midpuberty sufficient gonadal estrogen secretion leads to proliferation of the endometrium and the first menstruation (menarche) occurs First 1-2 years following menarche, cycles are anovulatory (but not always!) Term What happens for males durng puberty for the LH levels? Definition Normal LH pulse frequency and amplitude LH secretion leads to production of Testosterone by the Leydig cells in the testes. Growth of the testes is the first sign of puberty in the male Term What is a good test to see if puberty has becun? Definition whether or not GnRH has been stimulated Term During the ovulation (repro) period of a woman, do gonadotrophin levels vary? Definition yes Term What happens to gonadoptrophin levels during postmenarchy? Definition they increase Term What are 2 independent stages of puberty? Definition Adrenarche: increase in secretion of androgen precursors from the zona reticularis of the adrenal gland (DHEAS) leads to growth of axillary and pubic hair Not under direct control of ACTH Factors controlling adrenarche obscure Gonadarche: activation of sex steroid secretion by the ovary or testis leads to growth of breast tissue, sexual maturation Term Are adrenarch and gonadarche independently regulated? Definition Adrenarche occurs normally in individuals without functioning gonads (Turner Syndrome) Gonadarche occurs normally in individuals with primary adrenal insufficiency Premature adrenarche does not lead to premature gonadarche Term what are 4 stages in puberty? Definition Adrenarche Androgen production from adrenal gland Thelarche Breast development Pubarche Development of pubic hair Menarche Onset of menstruation Term When are the stages in pubertal development for girs? Definition between 6 years old and 12.8 Term When do most girls get breasts? Definition 98.8% of girls have first sign of sexual development between ages of 8 and 13 years Term When is menarche? what is really a response to? Definition Onset of first menstrual period Bleeding occurs in response to estrogen stimulus to the uterus Does NOT reflect mature ovulatory cycle Confirms patent utero-vaginal outflow tract Term When is average age of menarche? Definition 12.8 years Term What is growth spurt for girls dependent on? what horomones are involved? Definition Growth spurt is dependent on the onset of puberty Peak height velocity is attained in the majority of girls before they reach Tanner B3 and PH2 Average girl grows 2 - 3 inches during the 2 years following menarche Growth hormone, IGF-I, sex steroids involved Term What is involved in testicular growth? Definition Increase in size Sertoli cells cease to undergo mitosis Germ cells predominate in adult Leydig cells develop with LH stimulation Spermatogenesis first start age 11-15 (Tanner II-III) First conscious ejaculation mean age 13.5 Term What horomones are involved in male growth spurt? Definition Prepubertal growth velocity similar in boys and girls Puberty boys reach peak height velocity 2 yrs later than girls (Tanner III-IV) GH, IGF induced by gonadal steroids Term What are male physical changes? Definition Genitalia R testis larger than left Phallus 6.2 cm to 13.2 cm Vocal cords Membranous and cartilaginous components lengthen to 18-23 mm (vs 13-18 mm girls) Castrati vocal cords pre-pubertal length Facial hair Corners upper lip, cheeks then spreads to midline Axillary hair Occurs age 14 in boys (13 in girls) Acne fulminans Body changes Shoulders wider Legs grow before trunk Distal extremities grow before proximal Body composition Increase in lean body mass starts age 9.5 Adult men 1.5 times lean body mass, 1.5 times skeletal body mass vs females Term What are pfeiffer's heterosexist emotional changes? Definition Family conflicts increase Interest in opposite-sex companions increases while interest in same-sex companions decreases with pubertal maturation Increased ability and preference for abstraction Increase in imaginative responses Increased judgement Term Is the signal initiating puberty known? Definition no Term What has been known to stimulate pubertal changes in female monkeys? Definition pulsatile GnRH Term what factors influence the onset of puberty? Definition Genetic; Environmental; Toxic exposures; Nutritional status; Hormonal factors Term environmental Definition Earlier puberty associated with urban environment lower altitudes proximity to equator Term What are known toxic exposures? Definition Diethylhexylphthalate in low doses advances onset of puberty in male rats Flexible plastics Low dose stimulate androgen production Ge RS, et al. J Androl 2007 Tert-octylphenol administered neonatal period advances pubertal changes in female rats Paints, herbicides, plastics Binds estrogen receptors Willoughby KN, et al. Endocrine 2005 Term What does GnRH do? Definition GnRH pulsatile secretion by arcuate nucleus Pituitary/gonadal dependence on hypothalamic control Increase in this pulsatile secretion precedes and is responsible for gonadarche Term What giverns resumption of GnRH pulsatility? Definition GnRH control is extra-gonadal Agonadal primate and human models show increased GnRH pulsatility Candidates for neurobiologic control GnRH control may differ by sex// Model of restraining/braking is favored over stimulating in regulation of GnRH pulsatility Increase in GnRH expression modest at puberty GnRH mRNA and peptide similar before and after puberty GnRH gene constant Term what are upstream signals? Definition GABA Neuropeptide Y TGF-a Leptin Kisspeptin Glutamate CCK Term GABA Definition Receptor on GnRH neurons Key in female gonadarche “Inhibits” GnRH GABA declines as GnRH increases at gonadarche Inactivate receptor or reduce GABA elicits GnRH in prepubertal monkeys ? premature menarche and precocious first ovulation GABA agonist in 11-month girl with precocious gonadarche ? LH and pubertal develop regression Depakoate cases of delayed puberty in boys Term Neuropeptide Y? Definition Receptor in hypothalamus Key in male gonadarche “Inhibits” GnRH NPY mRNA and peptide content inverse to GnRH at infancy, juvenile and puberty NPY axons interact with GnRH perikarya NPY central administration arrests GnRH pulses in monkeys NPY can also stimulate GnRH release (?) Term Timing of puberty: NPY Definition Neuropeptide Y (NPY) in arcuate nucleus suppresses pulsatile release of GnRH and pituitary response to GnRH In absence of estrogen, NPY inhibits gonadotropin secretion Undernutrition associated with ? NPY ? leptin inhibits NPY in arcuate nucleus Term TGF-alpha Definition Role of glial cells in GnRH regulation Paracrine/autocrine release of prostaglandin E2 Prostaglandin E2 stimulatory to GnRH neurons TGF-a mRNA increased in female pubertal monkeys Term What does leptin do? Definition Receptor in hypothalamus and anterior pituitary Low level “required” for puberty Leptin increases in puberty Leptin soluble receptor decreases in puberty Clinically, leptin deficiency, leptin receptor defects ? hypogonadism But leptin does not induce precocious GnRH release (primates and human case) But leptin is not consistently elevated before GnRH pulsatility Term Timing of puberty: leptin Definition Leptin: hormone product of ob gene acts through functional receptors in the hypothalamus and serves as afferent satiety signal regulating appetite, body weight, sexual maturation Term Leptin and puberty Definition Leptin administration accelerates sexual maturation and puberty in normal female mice Females steady rise in leptin throughout puberty Males leptin peaks just before puberty Testosterone suppresses leptin Estrogen correlated with leptin Term kisspeptin Definition Kisspeptin is 121-aa protein Increased expression with puberty in monkeys Expression mostly in arcuate nucleus Metastin is 54-aa cleaved form of kisspeptin Carboxy terminal 10 aa (Kiss-10, Metastin 45-55) Pulsatile infusion ? LH pulses Continuous infusion ? decreased LH secretion (responds to glutamate and GnRH) Responses blocked by GnRH antagonist Term GPR54 Definition GPR54 is kisspeptin/metastin receptor G protein coupled receptor On GnRH neurons On Anterior pituitary Knockout mice ? no gonadarche Clinical cases of inactivating mutation ? delayed puberty/hypogonadotropic hypogonadism Term NMDA receptor Definition Glutamate and NMDA receptor Receptor on GnRH neurons (rodents) Glutamate increases at gonadarche in female primates Independent of Kiss/GPR54 pathway Term the signal that initiates puberty is unknown but... Definition restraint/braking control of GnRH is favored.