Therio - Hormone Control

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General series of events in theriogenology

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-mature from birth to puberty
--hormonal control of development of oocyte and sperm
---sexual behavior to induce the joining of oocyte and sperm
----fertilization
-----recognition and maintenance of pregnancy
------parturition
-------lactation and care of young

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Hypothalamus
-hormones

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-GnRH

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GnRH
-function

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-bind to gonadotrophs in the anterior pituitary release of LH & FSH

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GnRH agonists (Rx)

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-Cystorelin
-Factrel
-Fertagyl

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GnRH agonists
-uses

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-initiate ovulation (estrous synchronization of cattle)
-treat polycystic ovarian disease
-reduce fertility in wild animals

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GnRH control

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Gonadal steroids
-estrogen
-androgens
-progesterone

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GnRH control
-Rx

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-Mebolerone (synthetic androgen for estrus prevention in adult female dogs)

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GnRH travels to the anterior pituitary via

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-portal vessels

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LH
-function

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-convert follicular cells to luteal cells
-maturation of tertiary follicles and stimulates estrogen production
stimulates androgen synthesis by thecal cells

Front 10

LH surge
-function

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-inc. progesterone conc. in follicular fluid
-reactivate myosis of primary oocyte
-inc. estradiol, PGF2a, PGE2

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LH
-effect in male

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-stimulation of Leydig cells of testes to produce testosterone

Front 12

Chorionic gonadotropin
-types & effects

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-eCG (equine): LH and FSH
-hCG (human): LH

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Action of GnRH or eCG

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Release of LH
-ovulation/luteinization
-initiation of new follicular wave
-CL formation

Front 14

FSH
-function

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-stimulate follicle growth in ovaries
-stimulates estradiol production from granulosa cells of follicle

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FSH
-half life

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-several hours
-longer than LH (10 min)

Front 16

Prolactin
-produced where

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-anterior pituitary
-immune cells
-brain
-uterus
-others

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Prolactin
-function

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-acts with estrogens to induce lobuloalveolar growth of mammary glands
-stimulate milk production
-maintain CL in some species (dog, rodent)
-maternal behavior (nesting)

Front 18

Prolactin
-release antagonized by

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-dopamine from hypothalamus

Front 19

Oxytocin
-produced where

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-hypothalamus and secreted by nerve ending in the posterior pituitary

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Oxytocin
-function

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Smooth muscle contraction
-eject milk from mammary alveoli (released from tactile stimulation of teats)
-inc. uterine contractions during parturition (rise in estrogen increases the number of oxytocin receptors in myometrium)
-establish maternal behavior (rodents)
-facilitate sperm transport (male and female tracts)

Front 21

Oxytocin
-Rx
-use

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-Pitocin
-Oxytocin

-uterine contractor to precipitate and accelerate normal parturition and postpartum evacuation of uterine debris
-use post cesarean section to facilitate involution and resistance to large inflow of blood
-help with milk letdown

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Your client want to "superovulate" a female so that she produces more eggs than normal. What hormone should you give?

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-FSH

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How do the hypothalamic hormones reach the anterior pituitary gland?

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-short portal vessels

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Ovarian Follicle
-hormone secreted

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-Estrogen

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Estrogen
-function

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-positive feedback loop with LH
-acts on the brain to initiate estrous

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Ovarian follicle

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When can primary follicles start becoming secondary follicles?

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-puberty

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Pituitary dependent phase of follicular growth
-describe

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-FSH
-growing follicles are stimulated to undergo further growth and maturation
-increased number of granulosa cells
-liquor folliculi moves between granulosa cells

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-follicle type
-letters

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Graafian follicle

-A: basal lamina
-B: theca interna
-C: theca externa
-D: antrum filled with follicular fluid
-E: corona radiata (after ovulation)
-F: granulosa cells
-G: cumulus oophorus
-H: primary oocyte (mare, dog); secondary oocyte (other species)

Front 30

Progesterone
-produced where

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-granulosa cells
-theca cells

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Intrafollicular progesterone
-precursor for

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-testosterone
-estrogen

Front 32

Steroid hormone production from cholesterol
-flow
-produced from

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-cholesterol
--progesterone
---testosterone
----estrogen

-cholesterol from liver
-hormones from adrenal glands and gonads

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PGF2a
-produced where

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-uterus
-non-pregnant endometrium

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PGF2a
-function

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-lyse CL
-initiate process to ovulation

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PGF2a
-Rx

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-Lutalyse
-Estrumate

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PGF2a
-reason to use

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-lyse a mature CL (diestrus) causing a decline in progesterone production by the CL

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PGF2a
-side effects in horses

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-sweating
-colic
-trembling

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Induced ovulator
-definition

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-require stimulation in order to ovulate (copulation, genital stimulation)

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Induced ovulator
-example spp

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-rabbit
-cat
-camel
-ferret

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Hormonal effect of copulation in a queen

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-copulation stimulated LH secretion by anterior pituitary
-more copulations-->higher LH

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Progesterone
-produced where

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-CL

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Progesterone
-function

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-prepare the uterus for the egg
-acts on the brain to override estrogen and prevent estrus behavior

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Progesterone
-Rx

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-Melengestrol acetate
-Regu-Mate
-CIDR insert (natural)

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Why you rely on the fact that estrus behavior is not being seen to know if there has been ovulation?

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-more progesterone is needed to prevent ovulation than is needed to prevent estrus

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-Corpus luteum

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Graafian follicle
-what is it

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-large tertiary follicle that is ready to ovulate

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Testosterone
-formed where

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-Leydig cells in the interstitial spaces of the testis

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Testosterone
-conversion from cholesterol stimulated by

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-LH

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LH
-inhibited by

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-estrogen

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Hormone necessary for male farm animals to reach puberty

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-LH

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Hormones required for the induction of spermatogenesis during puberty

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-FSH
-LH

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Functions of LH and FSH in inducing spermatogenesis

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-LH stimulated testosterone production
--testosterone stimulates sertoli cells

-FSH decreases percentage of germ cells that degenerate during spermatogenesis

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Can spermatogenesis be sped up?

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-NO

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Spermatogonia
-chromosome number

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-diploid (2n)

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Spermatogonia
-effect of mitosis
-effect of meiosis

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Mitosis
-more spermatogonia

Meiosis
-differentiation to spermatocytes --> 4 haploid spermatids

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Length of time for spermatocytes to become spermatids

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-3 wks

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Length of time for spermatids to differentiate to sperm

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-3 weeks

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Importance of progesterone produced by placenta

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-if enough progesterone is produced by the placenta, a CL is not needed to maintain pregnancy

-human
-sheep
-cat

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Progesterone
-roles

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-support endometrium for fetal survival
-suppress contractility of uterine smooth muscle
-inhibit LH & FSH --> prevents ovulation during pregnancy

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Estrogen production by placenta
-function

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-prepare uterus for fetal expulsion (block progesterone)
-stimulate mammary gland development

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Placental estrogens
-derived from

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Depends on spp:
-fetal androgens
-placental progestins
-steroid precursors

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Chorionic gonadotropins
-function

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-invade maternal tissues and act similar to LH/FSH (pituitary gonadotropins)

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hCG
-function

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Human Chorionic Gonadotropin
-binds to LH receptros preventing CL regression

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Chorionic gonadotropins
-species found in

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-humans
-equine

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Placental lactogen
-function

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-relative of prolactin and oxytocin

-development of mammary gland prior to parturition
-stimulate CL function

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Placental lactogen
-species found in

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-primates
-ruminants
-rodents

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Relaxin
-function

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-maintain pregnancy
-relaxation of pelvic ligaments at end of gestation

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Relaxin
-produced where

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-placenta
-CL
-both

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Relaxin
-species that can produce a lot of hormone

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-Guinea pigs (large babies)

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What type of hormones are orally active?

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-steroid hormones

-protein hormones get digested

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Which species can maintain a pregnancy even if an ovariectomy is performed?

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-sheep