Lecture Notes for Reproductive Ageing

Objectives:
1. Overview of male and female reproductive system
2. Understand affects that aging has on fertility of men and women
3. Hormonal changes and symptoms of aging men and women
4. Advantages and disadvantages to hormonal replacement therapy

MALE REPRODUCTIVE SYSTEM:
- GnRH in hypothalamus signals to gonadotroph cells in the anterior pituitary
- Gonadotrophs release LH and FSH to act on the testes
- HPG (hypothalamic-pituitary-gonadal) axis controls reproductive function
- Reproductive function is switched off until puberty
- Reproductive function is developed through puberty and reaches full potential
during early adulthood (20s – 30s)
- At middle age, reproductive function declines as a steady rate
- Continues to decrease until death
- Continuous production of sperm throughout life relative to the reproductive function
- Testosterone is released by the Leydig cells in the testes (located between
seminiferous tubules)
- Production of sperm = spermatogenesis
o Which begins at puberty
o Makes roughly 400 million sperm cells every day
- Spermatogenesis is regulated by FSH + testosterone in the seminiferous tubules
- Seminiferous tubules contain spermatogonial stem cells and Sertoli cells
o Spermatogonial stem cells divide + differentiate into new
sperm cells
o Sertoli cells are regulatory + important for support,
nutrition, protection + regulation
- FSH stimulates inhibin release from Sertoli cells to begin the
negative feedback loop on FSH

FEMALE REPRODUCTIVE SYSTEM:
- GnRH in hypothalamus signals to gonadotroph cells in the
anterior pituitary
- Gonadotrophs release LH and FSH to act on the ovaries
- HPG (hypothalamic-pituitary-gonadal) axis controls reproductive function
- Reproductive function is switched off until puberty
- Reproductive function is developed through puberty and reaches full potential
during early adulthood (20s – 30s)
- At middle age, reproductive function declines as a steady rate
- Continues to decrease until menopause – then completely switches off for rest of life
- Ovarian cycles of oocytes and oocyte release continue through life relative to
reproductive function + completely switch off after menopause
- But there are limited oocytes in women
- All primary oocytes are generated from migratory germ cells during foetal
development
- Migratory germ cells are lost during foetal development  so cells that make
oocytes are limited = oocytes are limited

Neuroendocrine Aging
Gestational Diabetes

, o Also means there are no migratory germ cells post-birth
o Before birth = 7 million oocytes
o Birth = 2 million oocytes
o Puberty = 400,000 oocytes
o Menopause = less than 1000 oocytes
- Most of ovarian tissue is stroma
- Dotted within the stroma = ovarian/primordial follicles that contain oocytes
surrounded by squamous follicular cells (then stroma)
o Follicles are generated before birth + are dormant/inactive during childhood
- Ovarian cycle = changes and interactions between LH, FSH, oestrogen + progesterone
- Oestrogen + progesterone are steroid hormones that are released from ovaries at
different levels throughout the cycle
- Cycle:
o Follicular phase = FSH stimulates follicles to grow  day 1-10
 Primordial follicles are dormant + surrounded by flat granulosa cells
 Roughly 100 – 1000 follicles are activated during this phase
 Become mature follicles by FSH
 FSH is limited so causes follicles to compete for enough FSH
 Weaker follicles die off (atresia) + only 1 follicle is
left by day 10
 FSH stimulates inhibin release from follicle 
negative feedback signal to decrease amount of
FSH being released
 Because follicle + oocyte is mature and
ready
 Inhibin contributes to the competition of
FSH because it inhibits FSH
 Follicle left is large, has theca cells and granulosa cells surrounding it,
and releases oestradiol (type of oestrogen)
 Oestradiol is released in response to the LH acting during this
phase
 Release of oestradiol causes [general] oestrogen levels to increase
o Ovulatory phase = oocyte is released into fallopian tubes  day 11-14
 Oestradiol has a positive feedback effect during ovulation
 Usually has a negative feedback effect on LH and GnRH
 But during ovulation  stimulates GnRH +
LH release
 Generates the surge in LH which triggers
ovulation
 Oocyte is release but all other follicular cells
remain in ovary
o Luteal phase = LH + FSH fall and progesterone increases
 day 15-28
 Follicular cells remaining collapse + form the corpus luteum
 Corpus luteum produces oestrogen + progesterone for possible
pregnancy
 Corpus luteum is upheld until day 28/end of cycle

Neuroendocrine Aging
Gestational Diabetes