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Puberty and Menopause
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University of Edinburgh lecture notes for Reproductive Biology 3 lecture "Puberty and Menopause".
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Puberty and Menopause• Hypothalamo-pituitary gonadal axis (HPG axis)
o Both puberty and menopause are controlled by the HPG axis
o GnRH is released from the hypothalamus and acts on the anterior pituitary
o LH and FSH are secreted from the anterior pituitary into the blood
▪ LH and FSH can then be carried to the gonads
o Steroids and peptides feedback on the hypothalamus
▪ Steroids- testosterone in males and oestradiol in females
▪ Peptides- Inhibin B from Sertoli cells regulating FSH in males, and inhibin
B in the early follicular phase for females, then both inhibin A and B in
later stages
o
• Kallman’s syndrome
o Isolated GnRH deficiency
o Leads to delayed or absent puberty
o Long arms and legs- unicord stature
▪ Relatively tall individual
o Bones carry on growing without fusion of epiphyses at the end of bones during
puberty
• Lots of factors regulate GnRH secretion
o Kisspeptin found to be key driver of GnRH
o Dynorphin and neurokinin B also found to regulate GnRH secretion
▪ Dynorphin inhibits GnRH secretion
• Type of opioid, so some drugs can affect GnRH action
▪ Neurokinin B stimulates kisspeptin which stimulates GnRH secretion
o
, • Transition to sexually mature adult
o Adrenarche- maturation of the adrenal cortex with sex steroid production
o Puberty- HPG axis activation
▪ Causes menarche in females and 1st ejaculation in males
• Adrenarche
o Adrenal cortex is activated around 8 years old
o Increased secretion of steroids from zona reticulosa
▪ DHEA, androstenedione and testosterone all secreted
▪ Can be converted into more active androgens
o Adrenarche has an unknown role but could cause pubic/axillary hair
▪ It is not associated with the time of puberty
• Gonadotrophin secretion
o Neonates have some HPG axis activation in the first few months of life
▪ High production of FSH in females
▪ High production of LH in males
o Replaced by period of quiescence in childhood
o At puberty, levels of FSH and LH rise in both males and females
▪ LH is released in a pulsatile manner
o
o LH secretion is activated initially as night pulses
▪ Increase in LH secretion between pre-puberty and early puberty
▪ As puberty progresses, pulses spread across the full 24 hours
• Pulses over 24 hours continue into adulthood
▪
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