Reproductive
Endocrinology
Animal Breeding
Pensacola Jr College
Endocrinology
w Endocrine Glands = ductless
glands that secrete hormones directly into the bloodstream
w Hormone = molecule carried
by blood to target organ, binds to receptors, regulates an activity
Hormone Types
w Protein hormones
Large
Have cell surface receptors
Break down if given orally
w Steroid hormones
Small
Have internal cell receptors
Absorbed if given orally
Endocrine Control
w Negative feedback = hormone
exerts negative control over earlier steps in chain
w Positive feedback = hormone
exerts positive control over earlier steps in chain
Example of
Feedback Theory
Endocrine
Reproductive Glands
Endocrine
Reproductive Hormones
Female Repro
Hormones
w GnRH made in nerve cell
bodies in hypothalamus ΰ portal vessels ΰ carried to anterior pituitary
w Stimulates LH and FSH
production in ant. pituitary ΰ carried to ovaries
Female (contd)
w LH in ovaries:
Causes ovulation
Stimulates CL formation
Stimulates luteal cells to
produce progesterone
w FSH in ovaries:
Makes follicles grow
Stimulates granulosa cells
to produce estrogen, inhibin
Female hormone
feedback
w Progesterone has negative
feedback on LH, FSH, GnRH
w Inhibin has negative feedback
on FSH
w Estrogen
small doses have negative
feedback on LH, FSH, GnRH
Large dose positive
feedback
Female repro
steroids
w Estrogen = the cycle /
preparation hormone
Female development
Cyclical changes in the
reproductive tract, estrus cycle
Mating behavior
Mammary tissue growth
(ducts)
Female repro
steroids
w Progesterone = hormone of
pregnancy
Inhibits mating behavior
Maintenance of pregnancy
(uterine endometrial growth, stops cycling)
Mammary tissue growth
(glandular)
Male Repro
Hormones
w GnRH made in nerve cell
bodies in hypothalamus ΰ portal vessels ΰ carried to anterior pituitary
w Stimulates LH and FSH
production in ant. pituitary ΰ carried to testes
Male (contd)
w LH in testes:
Receptor sites on leydig
cells
Stimulates testosterone
production
w FSH in testes:
Receptor sites on sertoli
cells
Stimulates ABP (binds T) and
inhibin production
Stimulates sperm formation
Male hormone
feedback
w Testosterone has negative
feedback on LH, FSH, GnRH
w Inhibin has negative
feedback on FSH
Male repro steroid
w Testosterone
Development and maintenance
of all the male ducts, glands, etc.
Spermatogenesis
Seminal fluid production
Male sexual behavior
Prolactin in
Reproduction
w Produced by anterior
pituitary
w Controls milk production
w Controls reproduction in
many seasonal breeders
Increases LH receptor sites
on CL ΰ increases progesterone
Thus, low prolactin delays
implantation
Control of
Prolactin
w Pineal gland produces the
hormone melatonin at high levels during darkness
w Lots of melatonin during
short daylength (fall/winter)
w Melatonin inhibits prolactin
w Increasing daylengths thus
allow increased prolactin
Oxytocin in
Reproduction
w Produced by hypothalamus
cell bodies
w Carried on nerve fibers to
posterior pituitary for storage
w Functions:
Contractions of uterus in
birth
Milk ejections in lactation
w Positive feedback loop from
nerve stimulation