Puberty

ASCI 442

puberty

state gonads come to maturity relative to their exocrine and gametogenic potential

male puberty attainment

sexual behaviors appear

first ejaculation/spermatozoa first appear in ejaculate

spermatozoa appear in urine

certain concentration of sperm appear in ejaculate

female puberty attainment

first estrus

first ovulation

can support pregnancy

factors affecting puberty

genetics

nutrition

body size

melatonin (seasonal breeders)

before puberty (adrenarche)

only studied in humans

at 6-7 years old adrenal cortex secretes DHEA

occurs before gonadotropin and steroid synthesis

adrenal androgens induce sex hair development

independent of ACTH or gonads

regulation of GnRH

GnRH pulse is needed for female reproduction

before puberty - GABAergic neurons act on GnRH-releasing neurons (low GnRH release)

during puberty

• kisspeptin neurons turn on (increase GnRH release)

• E2 —| GnRH

• high E2 activates kisspeptin neurons in the AVPV (GnRH surge → LH surge)

kisspeptin

small protein hormone, released by hypothalamic neurons

binds to GPR54 (7TM Gq → IP3/DAG)

secretion increased by leptin

before puberty

ONLY GABAergic neurons act on GnRH releasing neurons

GABA —| GnRH

low GnRH pulse

after puberty, before negative feedback

Kisspeptin Neurokinin B Dynorphin (KNDy) neurons activate GnRH releasing hormones

higher GnRH pulse

after puberty, negative feedback

KNDy neurons —| estradiol

lower GnRH pulse

after puberty, GnRH surge

estradiol activates kisspeptin neurons in AVPV

affect of nutrition on puberty

leptin stimulates (kisspeptin) GnRH

glucose sensing neurons in surge center synapse on GnRH neurons

pineal gland and puberty

pineal gland releases melatonin (input from retina)

more melatonin released in the dark

effect of melatonin depends on species (long/short day breeders)

long day breeders

spring cyclicity, anestrus in fall and winter

horses, 11 mo gestation

melatonin —| GnRH

serotonin stimulates gonadotropins

short day breeders

fall cyclicity, anestrus in spring and summer

sheep, goats, deer, 6 mo gestation

Melatonin stimulates GnRH, activates release

mares

80% seasonal

2-3 30-40d estrous cycles coming into season, cycle stabilizes at 21d

10% non seasonal

10% seasonal and erratic

seasonal breeders puberty

photoperiod: offspring come into puberty during breeding season

precocious puberty

puberty before 8 in females and 9 in males

central: early maturation of HPG axis

peripheral: early maturation of gonads, independent of gonadotropins

increased growth velocity, advanced skeletal maturation, enlargement of ovaries and uterus, increased basal LH after GnRH surge

delayed puberty

absence of puberty by age 13 in females and 14 in males

hypergonadotropic hypogonadism

permanent hypogonadotropic hypogonadism

function hypogonadotropic hypogonadism