Endocrine System Drugs

Structure and function of endocrine system

Collection of organs and glands that secrete hormones into the bloodstream and stimulate action or stimulate another gland or organ to act. (chemical messengers)

What organs/glands are included in this system

Pituitary gland (master gland), thyroid gland, pancreas, ovaries, testes, parathyroid gland, hypothalamus, GI tract, Adrenal glands, Pineal gland

Endogenous

Naturally produced hormones (from within) into bloodstream

Exogenous

Hormones are administered to animal (from outside source), mammary glands, sweat glands, salivary glands, liver. To correct hormone balance, to obtain desired effect (induce ovulation)

Feedback Mechanisms (hormone regulation)

Nervous and endocrine system are coordinated by hypothalamus to control hormone levels in the body through 2 types of feed back mechanisms

What are the 2 types of feedback mechanisms

Negative feedback loops (high hormone levels detected) tells pituitary gland to stop producing hormone

Positive feedback loops (low hormone levels detected) signals pituitary gland to begin or increase hormone production

Pituitary Gland “master gland” divided into 2 lobes

Anterior pituitary: releases -trophic hormones, indirect-acting which cause another gland or organ to release hormones (messanger)

Posterior pituitary: releases vasopressin (anti-diuretic hormone) and oxytocin which are direct acting hormones

Endocrine Gland/Organ Abnormalities

Originate from peripheral endocrine gland/gland - primary disorders

Pituitary gland dysfunction (overproduction or underproduction of hormone due to hyperplasia/immune disorders etc) - primary or secondary

Abnormal tissue response to hormones, type || diabetes - not receptive to insulin - primary or secondary

Treatment for hyperfunction

radiation therapy, surgery, drugs to suppress hormone production

Treatment for hypofunction

replacement of peripheral endocrine hormone with exogenous source hormone

Estrogens

To prevent pregnancy after mismating, treat corpus luteum, expel mummified fetuses, induce abortion

Estradiol (EPC)

Used in mares to induce estrus, side effects: anemia, prolonged estrums, genital irritation, follicular cysts

Diethylstilbestrol

Capsules or tabs, sometimes used in dogs treat urinary inconsistence or if low estrogen

Progestins

Used in cats and dogs to suppress estrous and treat false pregnancy and some behavioural disorders. Act by mimicking progesterone.. can be absorbed through skin - caution pregnant woman, WEAR GLOVES!! Inhibit pituitary related of GnRH hormones.. can cause hyperglycemia

Megestrol acetate

Cats/Dogs Progestin

Alternogest (regumate)

Progestins - used to suppress heat cycle in mares before racing or young female pigs so they can all breed at same time

Androgens

male sex hormones used to treat urinary incontinence, increase libido and fertility in domestic animals (fairly useless), promotes weight gain, agression, rbc formation, secondary male characteristics development.. Ex, TESTOSTERONE

Oxytocin

made and stored in pituitary gland, Causes contractions in uterus, assist in fetal delivery and expel placenta, induces milk letdown, NEVER use in dystocia, cervix must be dilated first.. Ex Oxytocin

Prostaglandins

Synchronizing estrus in cattle, induce abortion or parturition, treat silent estrus, luteal cysts, and pyrometra in cattle .. Caution if pregnant or asthmatic .. WEAR GLOVES.. EX, Dinoprost OR Cloprostenol

Gonadotropins

Mimic 3 hormones (GnRH, LH, FSH), may be used to synchronize estrus in large animal medicine, suppress or induce estrus, treat cystic ovaries, terminate pregnancy

Gonadorelin

Treats cystic follicles on ovaries of cattle, has few side effects

Pheromones

Chemicals secreted by animals that influence the behaviour of other animals of the same species

Feliway

Similar to pheromone produced in feline facial glands- inhibit urinary marking by cats, reduce anxiety in cats in new environment

Dog Appeasing Pheromone (DAP)

Similar to hormone produced by nursing bitches, used for stress caused by transport, boarding kennels, new environment .. available as collar, spray, plug in diffuser

Thyroid gland

Located on trachea, needs iodine to function, stimulated by TSH from pituitary to release. Triiodothyronine (T3) active form. Thyroxine (T4) converts to T3 after release. - control metabolic rate, body temp, HR, immune function + more

Hypothyroidism

Lack of thyroid hormone, common in DOGS