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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 (cont’d)

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 (cont’d)

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