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27 Cards in this Set
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(1) what does the pulsatile release of GnRH cause?
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pulsatile release of FSH & LH
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(1) describe luteal phase (2) follicular phase
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CL produces protesterone > (-) feedback hypothalamus > slow GnRH pulse freq > slow LH pulse freq (1/6hr) > NOT STIM to follicles
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increase LH pulse freq (1/1hr) > follicles develop > produce estradiol > (-) feedback to pituitary (decrease pituitary responsiveness to GnRH)
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(3) what happens in an LH surge?
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increase LH pulse freq (1/1hr) > follicles develop > produce estradiol > increases secretion of GnRH by hypothalamus > increases pituitary responsiveness > LH surge > ovulation > luteinization > luteal maintenance (H, prolactin) > luteolysis (PGF2a)
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GnRH: (1) structure & function (2) names
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release is pulsatile, promotes pulsatile release of FSH & LH, but continuous GnRH leads to receptor desensitization and down regulation
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synthetic GnRH = gonadorelin (cystorelin or Factrel)
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GnRH: (1) uses (2) primary use
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management of infertility, suppression of gonadotropin with gonadorelin (termination of estrus in ferrets), differentiation of pituitary and hypothalamic defects in dogs w/hypogonadotropic hypogonadism, identify intact animals from enutered ones by estimating gonadorelin-stimulated release of FSH and LH
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INDUCE FOLLICLE DEVELOPMENT/OVULATION AT THE TIME OF BREEDING IN CATTLE AND HORSES
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(1) how is gonadorelin used to manage infertility? (2) protocol for AI
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induce follicle development/ovulation at the time of breeding (cattle, horeses), treat low libido (stallions), induce estrus in dogs/cats w/prolong anestrus, treatment of ovarian follicular cycsts (cystic ovaries in cattle)
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synchronization of estrus for timed AI: day 0 = GnRH (ovulate), day 7 = PGF (luteolysis), day 9 = GnRH (ovulate), day 10 = AI
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Gonadotropins: (1) name (2) how are they related
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Luteinizing hormone (LH), follicle-stimulating hormone (FSH), human chorionic gonadotroping (HCG), pregnant mare serum gonadotropin (PMSG)
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HCG = LH analog, FSH replaces eCG/PMSG
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(1) HCG use (2) FSH use
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treatment of F horses w/hypogonadism and to hasten or induce ovulation, treatment of cystic ovaries, treat M infertility due to impotence by stimulating testosterone secretion, treatment of cryptorchidism when one or both testes fail to descend
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treatment of F cattle to induce follicle growth and in conjunction with hCG to cause follicle ovulation (replaces eCG/PMSG when unavailable) - may be used to superovulate cows for embryo collection for embryo transfer
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Gonadotropins (1) toxicity (2) other preperations
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immune reactions (anaphylaxis); prolonged usage produces loss of efficacy b/c of circulating antibody
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human menopausal gonadotropin (HMG) approximates FSH & LH actitivies, PMSG = equine chorionic gonadotropin (eCG) but FSH > LH activity in this is more effective, but availability is variable
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Progestins (1) name (2) general function
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altrenogest (regumate, allyl-trenbolone), melengestrol acetate (MGA), CIDR (controlled internal drug release; Eazi-breed for cattle, CIDR-S for sheep, CIDR-G for goats), Synchro-Mate B (SMB)
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progestrin like negative feedback to hypothalamus
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Altrenogest (1) describe (2) protocol
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a synthetic, orally-active progestin used to controll estrous cycle and estrus of mares and pigs
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mare (PO 15d to induce regular cycles following winter anestrus and correct prolonged estrus, followed by PGF2a to induce estrus and ovulation; use low dose to minimize abortion; contraindicated in pregnant mares due to high doses = fetal abnormalities), pigs (PO 18d to synchronize estrus in gilts prior to AI; 95% estrus 4-7d after altrenogest withdrawl, only drug available for pigs, no PGF2a b/c pigs insensitive)
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Melengestrol acetate (1) describe (2) protocol
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synthetic progestin used as a feed-additive to synchronize estrus in cattle; synchronize estrous cycles in breeding females & suppress estrus in feedlot heifers
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fed for 11-14d, after removal of MGA, estrus and breeding 48-72hrs later or treat with PGF2a @ 17-19d post MGA withdrwal, check estrus/breed 1-5d later
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CIDR (1) describe (2) protocol
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T-shaped impregnated plastic device for synchronization of estrus improve efficiency of breeding programs. Effective anytime in the cycle, must be used with PGF2a for success (mimics CL)
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place intra-vaginally in dairy heifers for 7d, on day 6 dose with PGF2a IM, remove CIDR on day 7, triggers estrus within 3 days
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Synchro-Mate B (1) describe (2) protocol
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progestin (norgestomet)-estrogen (estradiol valerate) combination. Not in USA due to estrogens in FA. Synchronize estrus for heifer or post partum cows, for breeding by AI (or service)
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animals given ear implnt for 9d, injection of norgestomet (inhibits LH & FSH, follicle development and corpus luteum function) & estradiol valerate (stimulates PGF2a > luteolysis) IM
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(1) what drugs can be used to terminate pregnancy? (2) what drug can be used throughout pregnancy?
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prostaglandins, prolactin secretion inhibitors or dexmethasone, prostaglandin and prolactin inhibitors, progesterone antagonists, isoquinolones or progesterone synthesis inhibitors
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multiple doses of prostaglandins
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(1) what drug can be used to terminante pregnancy in second half of pregnancy only? (2) inhibit action of progesterone by blocking receptors?
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multiple doses of inhibitors of prlactin secretion or dexamethasone
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progesterone antagonists (mifepristone = RU 486) very expensive
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(1) what drug that is used for cushings can be used to terminate pregnancy?
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isoquinolones or progesterone synthesis inhibitors (epostane/trilostane)
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(1) where are prostaglandins (PGF2a) produced and used? (2) when does Prostaglandin (PGF2a) naturally occur?
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lining of uterus and tranfered to corpus luteum via uterine vein to ovarian artery to destroy CL tissue (unusual local circuit)
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luteolytic agent produced by endometrium during estrous cycle and produced at parturition to promote myometrial contractility and expulsion of the fetus
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(1) what is PGF2a used for?
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decrease estrous cycle length to synchronize estrus (except pig where CL not response for most of cycle), induce abortion and parturition in bitches, stimulate uterine contractions to facilitate placental delivery at birth in cows, treat endometritis associated with uterine infections via luteolytic and ecbolic efffects in mare and cow and bitch
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oxytocin (1) describe (2) uses
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cyclic nonapeptide that is structurally similar to vasopressin: uterus (stimulates frequency and force of uterine contractions) & mammary gland (stimulates milke ejection in response to suckling)
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induction of labor in small, large, and exotics (assist parturition, induce early or timed parturition, encourage post-partum uterine involution and emptying), milk letdown (stimulate milk letdown in bitches, oxytocin intranasal spray), side effects (toxicity uncommon, overdose or repeated dosing = painful contractions, uterine rupture, fetal death
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estrogen (1) describe (2) uses
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estradiol-17B is major ovarian estrogen in females (others: estrone in ovary, estriol in placenta). In blood bound to sex hormone-binding globulin (SHBG), metabolized in liver. Semi-synthetic = ethinyl estradiol), synthetic estrogens (mestranol), or non-steroidal derivatives (diethylstilbestrol, DES)
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functions: normal F repro phenotype/behavior and feedback suppressor of pituitary LH/FSH secretion. Used for hypogonadism, postmenopausal symptoms (humans), oral contraceptives (humans), carcinoma of prostate, prevention of conception (post coital treatment in humans and bitches)
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estrogen (1) toxicity (2) vet uses
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in humans (chronic estrogen) - breast cancer, endometrial hyperplasia, breakthrough bleeding, uterine carcinoma
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NOT widely used in food animals (residues): extradiol benzoate - treatment of postpartum cow, estradiol valerate (in Cynchro Mate B) estrus synchronization if heifers and postpartum cows (not in USA), diethylstilbestrol (DES) - urinary incontinence and perianal gland adenoma in dogs
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androgens (1) name primary & describe (2) function
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testosterone - principal circulating androgen in males; secreted by Leydig cells of testes in response to LH
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regulates male reproduction and sexual differentiation, physiological effects in adults mediated by dihydrotestosterone (DHT), testosterone also converted to estradiol (overall = androgenic and anabolic effects)
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androgens as anabolic steroids: (1) name (2) uses
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alkylated agents (stanazolol, fluoxymesterone, oxymethalone, norethandrolone), non-alkylated agents (nandrolone, methenolone)
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increase athletic performance (muscle size, strength, RBC production) in horses, treatment of aplastic anemia and myeloproliferative diesease and lympoma (stimulates erythropoietin and erythrocytes but only 1/3 cats/dogs show positive response), stimulates appetite (via positive nitrogen balance but may take weeks to months)
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anabolic steroids: (1) name (2) describe
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stanazolol (Winstrol-V), nandrolone (19-nortestosterone)
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side effects: hepatotoxic, weight gain, sodium/water retention, exacerbate azotemia, hypercalcemia, hyperphosphatemia, hyperkalemia. Contraindications: benign prostatic hypertrophy
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benign prostatic hypertrophy (BPH) (1) describe (2) treatment
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spontaneous and age related disorder of >80% of intact male dogs > 5yrs; linked to androgenic activity of DHT (enlargement of prostate gland). Clinical signs = sanguinous prostatic fluid, constipation, dysuria
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castration, anti-androgenic agents (finasteride or flutamide). Finasteride doesed for 16 weeks
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describe (1) finasteride (2) flutamide
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(proscar) irreversible 5a-reductase inhibitor blocks the conversion of testosterone to DHT = drug of choice for BPH. Side effect = impotence but did not affect semen quality or serum testosterone concentrations
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androgen receptor antagonist
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