Secretes substances which act at the site

Ducts

Seceretes substances which have actions at distant points, no ducts

Uses blood

Cellular communication systems somewhat like nervous system

Slower, mail vs. email

Secerete hormones, substances which are released into the bloodstream and have effects elsewhere in the body

Mediated by receptors on target cells, match hormone with receptor on cell

By structure

Peptides/Proteins: Insulin

Steroids: Estradiol

Amino Acid Derivatives: Thyroid

Fatty Acid Derivatives: Prostaglandis

Can be stored in secretory vessicles, released in a large bolus on signal, secretion as synthesixed

Many have short lifespan after release, inactivated rapidly, similar to neurotransmitters

The concentration

Concentration depends on the rate of synthesis, the rate of destruction, and the rate of delivery

Regulated by feedback loops

Similar to a thermostat

Effect produced by hormone acts to further production/release of that hormone

Results in a pulsed release of hormones

Variable concentrations in blood depending on sample

Hypothalamus sends out thyroid releasing hormone

The pituitary releases thyroid stimulating hormone

Thyroid gland sends out thyroid hormones

Thyroid hormones reach hypothalamus

Too much, stop released thyroid releasing hormones

Interface between nervous and endocrine systems

Temp, blood/fluid regulation

Close anatomical relatioship with pituitary via nerve fibers and release of hormones

Tyrosine->Tri-Iodothyronine->Thyroxine

Affects the uptake of oxygen by all the cells, esstential for normal growth

Near or embedded in thyroid gland

Works with calcitonin to regulate serum calcium

Primary, Secondary, or Nutritional

Sit on kidneys

Outer

Glucocorticoids

Mineralcorticoids

Inner

Adrenaline

Noradrenaline

Endocrine/Exocrine

Insulin and glucagon

Near optic chiasma

Various housekeeping functions

Sleep/wake, appetite, thermoregulation

Coordination of endocrine system->secretion of releasing/inhibiting hormones

Pituitary connects with hypothalamus

Vascular nerve input from hypothalamus to pituitary

Portal system to anterior pituitary

Neural input to posterior pituitary

STORED IN HYPOTHALAMUS, RELEASED IN PITUITARY

Anterior/posterior

Different embryologic origins

Anterior: Glandular tissue, hormones produced under direction of hypothalamus

Posterior: Neural

Growth hormone

GHRH from hypothalamus, GH from A.P.

Anabolic (+) effects on protein metablosim

Catabolic (-) effects on adipose tissue

Insulin-like growth factor production by liver

Induces growth of alveoli of mammary gland

Stimulates lactogenesis

Effects on maternal behavior

BST: cow growth hormone->milk production

Thyroid stimulating hormone

Thyrotropic/Thrytopin

Stimulates growth and activity of thyroid gland

Adrenocorticotropic Hormone

Release initiated by CRF

Stimulation of growth and activity of adrenal coretex

Feedback Loops to hypothalamus and pituitary for regulation

CNS can also release ACTH in emergency

Melanocyte-Stimulating Hormone

Stimulates color changes in amphibians and reptiles

Receptor for MSH seems to be involved in coat color in mammals

Follicle Stimulating Hormone

Stimulates development and growth of ovarian follicles

Estrogen secretion by follicles

Spermatogenesis by males

Storage and release of two peptide hormones produced by hypothalamus, ADH and oxytocin

Transported in nerve fibers which originate in hypothalamus, stored in nerve endings

Released by nerve impulses

Antidiuretic Hormone, vasopressin

Acts on kidneys to promote reabsorption of water

ADH insufficiency, central diabetes insipidus

Uterus-contractions

Mammary-myoepithelial cells

Sperm transport

2 Lobes, lateral to larynx, isthmus

Composed of follicles-spherical cuboidal epithelium, contains thyroid hormone precursor made by cells, thyroglobulin

C cells inbetween follicles->calcitonin, parafollicular cells

Synthesis/secretion regulated by hypothalamus and pituitary

T3 more active

Acts on virtually all cells of the body, increases basal metabolism, body heat, HR, contraction, output, necessary for normal growth, effects on fertility and hair coat

Transported by being bound to proteins in blood

Metabolized by removal of iodine

Hypothyroidism: most common endocrine disorder in dogs, primary or seconday

Hyperthyroidism: most common endocrinopathy of cats, primary, middle age/senior cats

Most commonly a lymphocytic thyroiditis, autoimmune

Labs predisposed-greasy coat

Clinical signs, increase in weight, decrease in activity, greasy coat, slow, cardiac and neuromuscular

Adenomatous Hyperplasia-thyroid gets bigger

Mature/Older cats

No breed dispositions, geographical-east coast

Clinical signs, decrease in weight, increase in appetite, crabby, greasy skin, rapid cardiac, muscle wasting

Enlargement of the thyroid gland in an attempt to increase secretion

Caused by iiodine deficiency, ingestion of goiterogenic plants

Made in various tissue in smallter amounts, but msotly from thyroid gland, C Cells, parafollicular cells

Peptide hormone

Helps regulate blood calcium levels

Inhibits release by suppressing osteoclast activity

Inhibits reabsorption in kidney tubules

Secretion regulated by levels in blood

Opposite effect of calcitonin

Main regulator of calcium and phosphorus lvls in serum

Protein hormone

Actions: mobilizes calcium from bone, increase calcium absorption in small intestines and kidney

Adjacent to cranial pole of kindey

Coretex and medulla

Mineralcorticoids

Glucocorticoids

Sex Hormones-Androgen, estrogen

Hypothalamus->AP->AC

Steroid hormones regulating electrolyte (sodium, potassium, chloride, phosphate) balence

Aldosterone-increases sodium retention

Cortisol, cortisone

Increase blood glucose levels

Catabolic effect->mobalize amino acids for gluconeogenesis, increase BP, antinflammatory, immunosuppressent, stress related functions

Derived from nervous tissue

Produces and secretes: adrenaline and noradrenaline

Regulated by SNS

Fight/flight respons

FASTER AND MORE IMMEDIATE RESPONSE

Insufficiency, autoimmune etiology

Lethargy, weakness, vomiting, weightloss

Synthetic hormone replacement

Iatrogrenic->cushings

AP secretes excess ATCH

Primary adrenal tumors in ferrets

Can be iatrogenic

Protein hormone, made by beta cells of pancreatic inlet

Secreted in response to high glucose lvls

The way animals store sugar, readily available

Plants->starch

Transport of glucose into cells of body

Brain/liver do not require insulin for glucose update

insulin stimulates the liver to store glucose as glycogen

Stimulates glycogen synthesis and storage in liver

Stimulates synthesis of fatty acids for storage in adipose tissue

Inhibits breakdown of fat in adipose tissue

Dextrose, simple sugar

Primary source of energy

80-120mg/dl

Ingestion of meal raises BG lvls, insulin release, BG lvls return to normal

Type 1: beta cells of pancreas do not produce insulin

Type 2: cells of body become resistant to insulin

Animals with DM, elevated BG lvls, glucose unable to enter cells

Body thinks it is starving even though there is plenty of glucose

Breaks down fat for energy, production of ketones may exceed body's ability to remove them

Medical emergency

Peptide hormone

Produced by alpha cells of pancreatic islets

Secreted in response to low lvls of BG

Acts on hepatocytes to break down glycogen to glucose

Stimulates gluconeogenesis, fatty acid breakdown in adipose tissue, cats very effecient