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Learning Reproduction in Farm Animals 

04-Endocrine Glands & Hormones

Learning Objectives:

  To understand what the reproductive endocrine glands and hormones are.

  To understand the characteristics and functions of these hormones.

  To understand how the concentrations of these hormones in the blood are controlled.

Endocrine Glands of Reproduction

  Body Diagram of Endocrine Glands 

  Brain Diagram of Endocrine Glands 

Endocrine Control of Reproduction

Hormone - Chemical messenger produced by a ductless gland or tissue and carried in the

blood to a target organ where it effects a change in cellular activity.

Chemical types of hormones:

Peptide - Few - Several amino acids

Protein - Long chains of amino acids

Glycoprotein - Protein hormone with carbohydrate molecules

Hormone Disappearance Rate 

Steroid Hormones - Sex Steroid Biosynthetic Pathway 

Synthetic Hormones 

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Fatty Acids 

Concept of Receptors: Cells of target organ have specific receptors for hormones.

  For protein & peptide hormones - receptor is in plasma membrane.

  For steroid homrones - receptor is in nucleus

  For prostaglanding hormones - receptor is in plasma membrane.

Hormone Receptor Activation 

d  Hormone  Chemical Class  Principal Functions 

yafian Follicle Estrogens (Estradiol) Steroid Mating behavoir, Secondarycharacteristics, Maintenance

female duct system , Mamm

growth

Inhibin (Folliculostatin) ProteinRegulates release of FSH fro

anterior pituitary

us Luteum Progestins (Progesterone) Steroid Maintenance of pregnancy,

Mammary growth & secretio

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Relaxin Polypeptide Expansion of pelvis

Dilation of cervix

s

dig Cells

Androgens (Testosterone) Steroid Male mating behavior,

Spermatocytogenesis, Maint

of male duct system & acces

glandsoli Cells Inhibin Protein Regulates release of FSH

nal Cortex Glucocorticoids (Cortisol) Steroid Induction of partruition by f

Milk synthesis

Stress response

nta Human Chorionic Gonadotropin 

(HCG)

Glycoprotein LH-like - Involved with

establishment of pregnancy i

human. Support and maintai

ometrial Cups

e

Equine Chorionic Gonadotropin 

(eCG)

Old name - Pregnant Mare SerumGonadotropin (PMSG)

Glycoprotein FSH-like- some LH activity

Immunological protection of

during pregnancy Formationaccessory CL in mare

Estrogens/Progestins Steroids Regulate placental bloodflow

Maintenance of pregnancy

Relaxin Protein Relaxation/dialation of cervi

parturition

Placenal Lactogen Glycoprotein Stimulates mammary growth

secretion.

ne Endometrium

fian Follicles

nal Vesicles

Prostaglandin F2 (PGF2)  Lipid Regression of CL

Stimulate myometrial contra

OvulationSperm transport

Insulin-like Growth Factors 

IGF-I & IGF-II

Protein Stimulates steroidogenesis,

Stimulates mammary growth

fetal development

al Gland Melatonin Biogenic amine Control of seasonal reproduc

Mare & Ewe

Regulate hair growth

rior Pituitary Oxytocin Octapeptide Stimulate myometrial contra

for sperm transport, parturiti

milk ejection

rior Pituitary Follicle Stimulating Hormone 

(FSH) - Follicotropin

Glycoprotein Stimulate follicle growth Sti

estrogen production

Spermiogenesis in male

Luteinizing Hormone (LH) -

Luteotropin

Glycoprotein Stimulate ovulation

Support CL formation, and

progesterone secretion Stimu

testosterone synthesis by ley

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cells of testis

Prolactin Protein Stimulate milk synthesis

Regulate metabolism for mil

synthesis

Effects Maternal Behavior

Adrenalcorticotropic Hormone (ACTH)

Protein Release of corticosteroids &glucocorticoids from adrena

to initiate parturition

othalamus Gonadotropic Releasing Hormone 

(GnRH)

Decapeptide Stimulates release of FSH an

from anterior pituitary

Dopamine Biogenic Amine Inhibits release of prolactin

Corticotropic Releasing Hormone 

(CRH)

Peptide Stimulates ACTH release

Growth Hormone-Releasing

Hormone (GRH)

Peptide Stimulates release of growth

hormone

Oxytocin  Octapeptide Produced by the hypothalam

released at the posterior pitu

Control of endocrine gland function.

Hypothalamus - Pituitary interrelationships. 

Hypothalamo-hypophyseal portal system caries hypothalamic hormones specifically

to the anterior pituitary without dilution in the systemic blood. 

Specific hypothalamic nuclei secrete releasing or release inhibiting factors that

control release of pituitary hormones. 

Preovulatory LH surge is controlled by gonadotropin releasing Hormone (GnRH)

from the surge center.

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