a chemical substance that is carried by the circulation from and endocrine gland in one part of the body to another part of the body where it exerts a specific observable effect
2 types of hormones
steroid hormones (made from fat), protein hormones(made from amino acids)
similar to hormones but not "exactly" like them. May mimic them to a certain extent like tofu(soybean) or certain clovers.. contains estrogen-like compound.
how hormones work
1. Leaves gland and enters bloodstream 2. Reaches "target tissue" 3. Binds to "receptor sites" 4. A specific response occurs in the cell
Controls other glands in the body by secreting hormones that either turn them on or off.
Connects pituitary gland to the ventral portion of the brain. Sends releasing factors or inhibitory factors to the pituitary gland by direct blood vessels
If levels of a particular hormone are low in the blood the hypothalmus senses this and tells the pituitary to send out releasing factors which turn on the gland that makes that particular hormone.
If hormone levels are found to be too high the hypothalamus tells the pituitary to send out inhibitory factors which tell the gland that makes the hormone to stop producing so much.
anterior lobe of the pituitary gland- produces 7 hormones
Posterior lobe of the pituitary gland- produces 2 hormones
Growth Hormone (GH)
Stimulates growth of body cells, especially bone and muscle. Causes protein synthesis and prevents protein breakdown. Increases milk production in cattle (bST).
Stimulates cortex of the adrenal glands to make cortisol/ cortisone which is needed in stressful situations
Thyroid Stimulating Hormone (TSH)
Stimulates the thyroid gland in the neck to make thyroid hormones
Stimulates milk production in females. Released in response to nursing offspring
Follicle Stimulating Hormone (FSH)
Causes follicles with eggs in them on the ovaries to grow near estrus cycles and make estrogen. Stimulates sperm production in males.
Luteinizing Hormone (LH)
Causes follicles on ovaries to rupture (ovulation). If not enough released some follicles don't ovulate and turn into "cysts." Stimulates testosterone production in testes in males.
Causes color change in reptiles, fish and amphibians to allow them to blend into their enviroment.
Anti-diuretic Hormone (ADH or vasopressin)
Makes collection ducts in kidney absorb more water from the urine to conserve water in the body.
Stimulates smooth muscle to contract. Helps in birthing process/ expel placenta. Uterus for sperm movement cranially. Udder for milk letdown.
Near hilus of kidneys. Has a cortex and medulla like the kidney.
Steroid hormones- made from cholesterol, are essential for life.
cortisol (natural), prednisone, cortisone, dexamethasone (synthetic). Increase blood sugar levels. Decrease inflammation. Helpful in times of stress to maintain homeostasis.
Aldosterone - Made in response to renin-angiotensin when water needs to be conserved. Causes sodium retention n PCT and water follows.
Male hormones- testosterone. Made by both sexes. Ratio of male to female hormones is improtant for sex drive in females
Hyperadrenocorticism- too many hormones especially cortisol. Pot belly, thirst, appetite, urination, weight gain.
Hypoadrenocorticism- Not enough hormones. Low blood sugar, weak, shake, V/D, easily stressed.
Catecholamines -Epinephrine/ Adrenaline, Norepinephrine. Fight or flight hormones. Needed daily to handle "stress."
Consists of 2 lobes often connected with a band of tissue. Fluid filled "follicles" make T3 and T4.
Tri-iodothyronine, the active hormone of the thyroid gland.
Thyroxine, the hormone of the thyroid gland that is usually measured in the lab.
T3 and T4
Exert a lot of control over metabolism. 1. Absorption and use of glucose 2. Synthesis of protein 3. Synthesis of cholesterol 4. Heat production 5. Need for normal growth and reproduction.
(Dogs and Humans). Lethargic, cold intolerance, weight gain, hair loss "rat tail," thick greasy skin, metal dullness, reproductive problems. Treat with T4.
(Cats and Humans) Fast metabolism, thin, tachycardia, hyperactive, bulging eyes (humans). Treat with surgery, radioactive Iodine, drugs- Tapazole.
Enlargement of thyroid. Due to excessive stimulation of thyroid gland by pituitary due to iodine deficiency. Due to tumor, due to excess iodine in diet.
On or near edges of thyroid glands (4 total). Make parathormone (PTH)- increases blood calcium. Stimulates osteoclasts to remove Ca+ from bones. Increases GI absorption of Ca++. Increases renal absorption.q
Exocrine function- amylase, lipase and trypsin. Endocrine function- Islets of Langerhans.
Alpha cells. Works opposite of insulin. Works to break down glycogen in liver to raise bood sugar levels when fasting or inappetance
Beta cells- forces glucose into cells for energy after we eat. Stimulates glycogen formation. Released in response to a rise in blood glucose after a meal. Not depended on pituitary gland.
P/U & P/D due to loss of glucose in urine. Juvenile and Adult onset.
Located in caudo-ventral neck area near base of heart. Seen in young animals, tends to atrophy with age. Makes hormones needed for normal develpoment of cellular immunity and WBC function.
Gland on the top of the brain. Makes melatonin at night. Helpful in nocturnal (especially reptiles) animals for night activity. Decreases gonad activity in winter.
length of day
Long-day breeders (spring and summer)
Short-day breeders (fall and winter)
Testes, Ovaries and Uterus
Interstitial cells make testosterone/sperm when stimulated by FSH and LH from the pituitary gland.
Leads to secondary sex characteristics. Voice change, heavy bones, thick neck, muscle development, sperm formation, sex drive.
Make estrogen and follicle cells around egg.
Gives female body shape, mammary development, signs of estrus.
Yellow body. Makes progesterone after egg as left follicle
Quiets uterus to prepare it for the fertilized egg. Stops further heat cycles if pregnant. Maintains pregnancy.Causes mammary development for milk production.
Hormone made by ovaries and uterus for pregnant animals. Blood tests for pregnancy in *****es after 21st day of pregnancy. Levels increase near parturition. Relaxes cervix, vagina, ligaments around birth canal- absorb more water.
Human chorionic gonadotrophin-- Urine pregnancy test kits.
Pregnant mare serum gonadotrophin - Made by endometrial cups in uterus of pregnant mare.
Found in blood of pregnant mare > 90 days with a healthy placenta/live fetus.
Many types made by different organs. Hormone of inflammation.
PG F 2 alpha
Made by non-pregnant uterus to start another heat cycle. Man made now also to help manipulate heat cycles. Causes luteolysis so progesterone levels drom and the hypothalamus senses it and causes the pituitary gland to release FSH
Made by the kidney to stimulate RBC formation in the bone marrow.
Stimulates pancreatic, bile and duodenal secretion of fluids to mix with ingesta
Stimulates pancreas to make enzymes
Stimulates the gall bladder to contract and send bile into the duodenum.