Puberty Flashcards
D: puberty
The transition phase that takes a person from being a sexually immature child to a sexually mature, reproductively fertile adult.
first signs of puberty?
do they show fertility?
- In females, menarche (first menstruation) is the most definitive sign.
- In males, first ejaculation (often nocturnal) is a sign of similar degree of maturity.
• These do NOT signify fertility, more a sign that the gonads have awakened and are beginning to assume adult levels of activity
- First menstrual cycles - anovulatory
- First ejaculate - small quantities of seminal plasma and no sperm
do boys have their growth spurt 2 years later than girls?
yes - hence taller
T or F
Lean body mass and body fat are virtually identical in prepubescent boys and girls
T
tanner stages female
tanner stages male
describe Cryptorchid testes
• Testicular descent occurs during fetal development
- 3-4% of males
- Impaired spermatogenesis
Puberty involves _____ activation of the reproductive axis
Puberty involves central activation of the reproductive axis
T or F
Puberty in primates involves re-awakening of the HPG axis
T
Puberty in primates involves re-awakening of the HPG axis
elaborate.
High gonadotrophic hormone levels in Rhesus monkeys during first 20 weeks of life.
HPG axis suppressed by GABAergic inhibition of GnRH release
At puberty, GABA inhibition removed and stimulatory inputs onto GnRH neurons.
This pattern observed in gonadectomized monkeys so not dependent on sex steroids
Puberty in primates involves re-awakening of the HPG axis
is it dependantn on hte sex steriods?
no
GnRH pulsatility ______ at puberty
GnRH pulsatility increases at puberty
Amplitude and frequency of GnRH pulses regulates LH and FSH levels
How?
does GnRH fluctuate more in adults?
no - mcuh less fluctuations
LH, FSH and oestradiol levels rise
Early cycles not associated with
……
LH, FSH and oestradiol levels rise
Early cycles not associated with
ovulation
Rise in ……..causes onset of spermatogenesis and rise in testosterone from testes.
Rise in FSH and LH causes onset of spermatogenesis and rise in testosterone from testes.
in males what causes growth of accessory sex glands and secondary sex characteristics
Androgens cause growth of accessory sex glands and secondary sex characteristics
Describe Growth hormone
- • Secreted from anterior pituitary in greater amounts near to puberty
- • Responsible (along with androgens) for growth of long bones and tissues
- • Major effect on protein synthesis and glucose homeostasis
- • GH deficiency => short stature, delayed sexual maturation
describe thyroid hormones near puberty
- Increase in secretion from thyroid gland, secondary to increased thyroid stimulating hormone (TSH) from anterior pituitary
- May account for rise in metabolic rate in both sexes
- Also essential for body growth
4 factors which can affect the onset of puberty
- Genetic
- Metabolic
- Social
- Environmental
how can GWAS be used to identigy genes associated with puberty ?
how else can we identify genes involved in puberty?
Genes affecting puberty can be identified by genetic association studies looking for regions of the genome that segregate with reproductive phenotype (eg precocious puberty in girls) – eg MKRN3.
Genes can also be identified by studying individuals that do not go through puberty and identifying the causative mutation eg. Kisspeptin, Neurokinin B pathways.
what do yo uknwo about MKRN3
normally Delays puberty:
• MKRN3 mutations cause early puberty.
Protein – big
Binds Zinc
Involved in protein degredation thorugh ubiquitin pathway
Cannot degrade GnRN = more GnRH released
how are Kisspeptins involved in puberty?
- kisspeptins encoded by the Kiss1 gene
- signal through Kiss1 receptors (G protein) Expressed by GnRH neurons
- Kisspeptin binding causes GnRH depolarisation and GnRH release
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