The Application of Endocrinology to
Selected Animals and Humans (Chapter
11)
• Efficient production – dependent on effective
bodily function
• Effective bodily function – dependent on
endocrine glands
Science of Endocrinology
• Endocrine glands – secrete hormones
• Ductless – release directly into blood stream
• Exocrine glands
• Ducts that lead to body surfaces or into other
organs
• Pancreas – unique organ that is both endocrine
(insulin) and exocrine (pancreatic juice into
stomach)
Science of Endocrinology
• Hormone – means “to stimulate”
• Secreted in very small quantities
• 1/1,000,000 g of oxytocin will cause milk ejection
• Important in:
• growth and efficiency
• reproduction
• lactation
Endocrine Glands
• Anterior pituitary
• Affects secretions of many other endocrine organs
• Posterior pituitary
• Stores and releases some hypothalamus hormones
• Hypothalamus
• Small area of brain that regulates hormonal activity
• Several others scattered around body
Chemical Nature of Hormones
• Proteins and glycoproteins
• Peptides
• Amines
• Steroids
• Non-steriodal
Hypothalmus Hormones
• Growth hormone-releasing hormone (GnRH)
• Stimulates release of growth hormone
• Growth hormone inhibiting hormone
(somatostatin)
• Inhibits release of growth hormone
• Prolactin-releasing hormone (PRH)
• Stimulates release of prolactin
Hypothalmus Hormones
• Prolactin-inhibiting hormone (PIH)
• Inhibits release of prolactin
• Oxytocin
• Ejection of milk, expulsion of eggs, uterine
contractions
• Vasopressin
• Constriction of peripheral blood vessels and water
resorption in the kidney tubules
Anterior Pituitary Hormones
• Growth hormone (GH, somatotropin)
• Promotes growth of tissues
• Adrenocorticotropin (ACTH)
• Stimulates secretion of steroids (especially
glucocorticoids (from adrenal cortex)
• Thyroid-stimulating hormone (TSH)
• Stimulates thyroid gland to secrete thyroxine
Anterior Pituitary Hormones
• Prolactin
• Initiates lactation and stimulates maternal behavior
• Follicle stimulating hormone (FSH)
• Stimulates follicle development in the female and
sperm production in the male
• Luteinizing hormone (LH)
• Maturation of follicles and ovulation in female,
testosterone production in testes by male
Thyroid Hormones
• Thyroxine, triiodothyronine
• Increases metabolic rate
• Calcitonin
• Lowers concentration of calcium in the blood and
promotes incorporation of calcium into the bone
Parathyroid Hormones
• Parathyroid Hormone
• Maintains or increases the level of blood calcium
and phosphorus
Adrenal Cortex Hormones
• Glucocorticoids
• Mobilizes energy, increases blood glucose, antistress
• Mineralocorticoids
• Maintains salt and water balance in the body
Adrenal Medulla Hormones
• Epinephrine
• Stimulates heart muscles and rate and strength of
their contraction
• Norepinephrine
• Stimulates smooth muscles and glands and maintains
blood pressure
Ovarian Follicle Hormone
• Estrogens
• Growth of the reproductive tract and mammary duct
system
Ovarian Corpus Luteum Hormones
• Progesterone
• Prepares reproductive tract for pregnancy, maintains
pregnancy and causes development of mammary
lobule-alveolar system
• Relaxin
• Causes relaxation of ligaments and cartilage in
pelvis, assists in parturition
Uterus Hormone
• Prostaglandin F2α (PGF2α )
• Causes luteolysis and a decrease in progesterone
Testicular Hormones
• Androgens (testosterone)
• Causes maturation of sperm
• Promotes development of male accessory glands
• Promotes development of secondary sex
characteristics
Pancreatic Hormones
• Insulin
• Lowers blood glucose
• Glucagon
• Raises blood glucose
Placenta (in some species) Hormones
• Gonadotropins, estrogen, progesterone
• Promotes maintenance of pregnancy
• Some names for placental gonadotropins
• Pregnant mare serum
• Equine chorionic gonadotropin
• Human chorionic gonadotropins
Functions of Hormones
• Small amounts needed
• Affect growth, body shape, food use,
reproduction
• Many quickly deactivated when administered
• May disappear in few hours
• Act quickly but effect may not be noticeable until later
Mechanism of Hormone Action
• Hormones released into, and travel through
circulatory system
• Attach to receptors that are specific to each
hormone
• Once attached to receptor, action will be carried
out in the cell
Regulation of Hormone Secretion
• Endocrine activity must be carefully balanced
• Regulation is important
• Feedback mechanism
• Interaction between two hormones may regulate
secretion of both
• Chemical homeostasis
• Blood level of non-hormone chemicals affected by
hormones may regulate secretion
Uses of Natural and Synthetic Hormones
• Birth control pills
• Many have combination of synthetic progesterone
and synthetic estrogen
• Synchronize estrus - Progestins, PGF2α
• Superovulation – Gonadotropins
• Treatment of cystic ovaries – Gonadotropin
releasing hormone
Uses of Natural and Synthetic Hormones
• Induction of lactation (not approved by FDA)
• Administration of estrogen and progesterone
• Increase rate and efficiency of gain
• Estrogens and synthetic estrogens
• Melengestrol acetate (MGA) – synthetic
progesterone
Hormones and Public Health
• Possibility of residues in food produced by
animals treated with hormones
• Has not become a public health problem
• Prevention of residues is high priority