hormonal/reproduction

master gland

pituitary gland is located in the hypothalamus, secretes inhibiting factors that signal the pituitary gland to secrete hormones that control other endocrine glands.

hormone

chemical substance produced by cells in one part of the body, where it influences and regulates cellular activity and organ function.

anterior pituitary

regulates animals growth and the proper functioning of its thyroid (TSH), gonads(FSH, LH (stimulated by GnRH gonadorelin)), cortical (ACTH), prolactin (milk production), pigmentation of skin (MSH), (GH) diabetogenic (muscle and adipose tissue) factor and growth factor (somatotropin). stimulated by blood neurohormones. released in pregnant animals as parturition approaches. ACTH causes cortisol to be produced by the adrenal cortex. Increased cortisol levels increase production of estrogen and prostaglandin by the uterus.

posterior pituitary gland

secretes antidiuretic (vasopressin) hormone and oxytocin (contractions and milk expulsion) that have been produced by the hypothalamus. stimulated by nerve control

antidiuretic hormone (ADH)

used to treat diabetes insipidus characterized by inability to concentrate urine, caused by insufficient release of ADH or failure for kidneys to respond to ADH. lack of results in increased thirst and urination (polydipsia/polyuria). Vasopressin injection is used to diagnose and treat diabetes insipidus. Desmopressin is similar but has more antidiuretic activity and does not affect urinary sodium or potassium secretions. used in conjunctival sac or intravenously to treat diabetes insipidus. Adverse effects include eye irritation and hypersensitivity reactions.

Oxytocin

Veterinarians use it to stimulate or enhance uterine contractions during parturition. This I especially helpful in the queen, bitch, and sow, where the possibility of manual manipulation of fetuses is limited. used to stimulate milk letdown. doesn’t have a milk or meat withdrawal time

Blood Glucose regulation

to remain healthy, animals must maintain blood glucose levels within a narrow, minimally fluctuating range. The two hormones that maintain blood glucose homeostasis are insulin and glucagon. Insulin, which is formed in the pancreas, is released in response to a rise in blood glucose. Insulin reduces blood glucose levels by promoting the movement of glucose from the blood into the cells where it can be used for energy and into liver storage in the form of glycogen (the chief form of carbohydrate storage in animals). Glucagon, in contrast, promotes the breakdown of liver glycogen into glucose, which exits the liver and enters the bloodstream, increasing blood glucose levels and the availability of glucose to provide energy for body functions.

Diabetes mellitus (DM)

a complex disease of carbohydrate, fat, and protein metabolism caused by lack of insulin or inefficient use of insulin (called insulin resistance) in animals. Animals with DM have elevated blood glucose levels (hyperglycemia), glucose in the urine (glucosuria), increased drinking and urination (PU/PD), and alterations in fat metabolism that can lead to toxic effects and diabetic coma. DM results in cell starvation in the presence of hyperglycemia, because in diabetic animals, there is not enough insulin to promote the movement of glucose into the cells. Cell starvation leads to the animal developing increased appetite and polyphagia, but weight loss continues because the cells are unable to use the glucose obtained from meals. When glucose levels in the blood are higher than about 200 mg/dL (a level that is common in animals with clinical signs of DM), it becomes too much for the kidneys to retain and glucose "spills" into the urine resulting in glycosuria. Glucose in the urine causes more water to be eliminated from the body along with it; water follows the glucose by the process of osmosis. The additional loss of water creates polyuria, a common clinical sign of DM, and compensatory polydipsia. DM, though recorded in all species, shows up most frequently (about 1 in 1000) in dogs, especially obese female dogs that are middle aged or older. The exact cause of DM in domestic animals is not known. In dogs, it is most commonly associated with the destruction of insulin-secreting cells in the pancreas by immune-mediated mechanisms, inflammation, or amyloid deposition. In cats, DM is often associated with inflammatory and amyloid-related destruction of insulin-secreting cells or with insulin resistance. In cats, remission of DM after a period of treatment with insulin and dietary changes is not uncommon, but in dogs, remission is rare. dogs are fed a diet high in fiber and cats are fed a diet high in protein. apply syrup to the gums if animal is experiencing severe hypoglycemia.

insulin production

Insulin has historically been extracted from bovine or porcine pancreas or a combination of both; however, bovine insulin is no longer manufactured. Currently there are two Food and Drug Administration (FDA)-approved insulin products for use in veterinary species: one extracted from porcine pancreas tissue and one human recombinant product. There are two insulin products approved for use in veterinary species by the FDA, and both products contain zinc

Neutral protamine Hagedorn (NPH) humulin-N, novolin-N, ReliOn-N

Neutral protamine Hagedorn (NPH) insulin is a human-approved insulin with an intermediate duration of action similar to the activity of veterinary approved insulins. onset (20-120min) duration (6-12 h for dogs). one of the most common used in vet field human-approved insulin. It is important to note that the veterinary-approved insulin products have a concentration of 40 units of insulin per mL, while most human-approved products have a concentration of 100 units per mL. If insulin is drawn up using a syringe, it is imperative that the syringe has been manufactured for the corresponding concentration of insulin. Insulin syringes are calibrated for specific concentrations and are not accurate with other concentrations of insulin.

Short-acting insulin (regular crystalline insulin) Humulin-R, novolin-R

is the only insulin given intravenously, and it can also be given intramuscularly or subcutaneously. Short-acting insulin is used initially in the treatment of diabetic ketoacidosis (DKA). DKA in an emergency condition resulting from metabolic derangements associated with chronic hyperglycemia and low insulin levels. To compensate for cellular starvation when insulin levels are too low, fat is released from the tissues and sent to the liver for use as an energy source. In the liver, fat may be oxidized into glucose, but when insulin levels are low, ketone bodies are produced from fat. Ketones such as acetoacetic acid cause acidosis, inappetence, and nausea. Signs of DKA include PU/PD, anorexia, vomiting, and weakness that can progress to coma and death. Regular insulin is used in cases of DKA to establish the initial control of blood glucose until the animal is stabilized. Short-acting insulin is not used in animals for long-term home management of DM. Short-acting insulin has an immediate onset of action when given intravenously with maximum effects occurring at 0.5 to 2 hours. Its duration of action varies depending on the administration route

Porcine (pork) insulin Vetsulin

is similar in structure to naturally occurring canine and human insulin. Recombinant human insulins are made by recombining (bringing together) genetic material from various sources to make DNA sequences capable of producing different types of insulins. The DNA sequence for insulin production is inserted into the genomes of bacteria, which then begin to produce insulin. Precipitation of insulin with zinc is used to extend its duration of action. Purified pork; long acting (30 to 120 min onset of action). SQ. 8-12 h duration for cats. 14-24 h duration of dogs It is used more often in dogs than in cats, and it is also typically administered twice daily.

Protamine and zinc insulin ProZinc

is a human recombinant insulin formulated with protamine and zinc to extend its duration of activity by slowing the rate of absorption after injection. protamine zinc insulin is approved for use in cats and dogs and is typically administered twice daily. long acting. onset of action (60-240 min). one of the most commonly used in vet field

insulin glargine; insulin analog; lantus, toujeo, Basaglar

recombinant human, long action. onset of action (60-120 min). duration (12-24 h) The use of insulin glargine in cats is associated with a good likelihood of remission. human-approved insulin

insulin determir; levemir

recombinant human. long acting. onset (60-120 min) duration (18-24 h). human-approved insulin

u 40

red tops. used in veterinary hospitals

u-100 

orange tops. used in human medicine

Diazoxide (proglycem)

oral hypoglycemic agent. prescribed treatment for patients with DM. hypoglycemia is associated with insulinomas (tumors of the pancreas) that cause increased secretions of insulin. glucagon is used to regulate blood glucose levels when they become low. labeled for oral use in treatment of hypoglycemia secondary to excessive insulin secretions by directly inhibiting pancreatic insulin secretion. monitor patients for signs of hyperglycemia, hypoglycemia or gastrointestinal problems. may also cause sodium and water retention and should be used cautiously in animals with heart or kidney disease.

Glipizide (Glucotrol)

sulfonylurea drug that promotes the production of insulin by the insulin secreting cells of the pancreas. not effective in dogs with DM usually have no functional beta cells. not a first line treatment of DM in cats but it is sometimes effective an may be prescribed when clients are unwilling or unable to administer insulin to their cat. adverse effects include GI distrubances, hypoglycemia, and liver toxicity.

drugs that increase blood glucose

glucocorticoids, epinephrine, and progesterone.

thyroxine (t4) and tri-iodiothyroinine (T3)

produced from iodide converted to iodine combining with tyrosine to form iodotyrosine. Sometimes T4 is converted into T3. thyroid hormone helps regulate lipid and carbohydrate metabolism, and influence heat production in the body.

hypothyroidism

may be caused by failure of thyroid to catch iodide and/or release of sufficient thyroid hormone from storage. may also be caused by dysfunction of the anterior pituitary gland in which inadequate amounts of TSH are released. clinical signs include decreased coat luster, hair loss, weight gain without any increase in appetite, listlessness, intolerance to cold, reproductive failure, and skin more susceptible to infectious disease. mainly occurs in dogs, rarely in cats. Thyroid stimulation test is more accurate for diagnostic. animal is injected with TSH. then check serum levels 4 to 6 hours after the TSH injection.

levothyroxine sodium (T4) (thyro tabs canine, synthroid)

synthetic isomer of T4. drug of choice for treating hypothyroidism in all animals. inexpensive and has a long half life, helps lower dosing frequency.

liothyronine sodium (T3) (cytobin, cytomel, triostat)

synthetic form of T3. is more expensive and has a shorter half life. used on animals that don’t respond well to levothyroxine.

hyperthyroid

increased metabolic rate, excessive heat production and increased nervous system activity. seen in cats. charcterized by increased thirst, weight loss despite increased appetite, increased stool produciton, restlessness (sometimes with increased vocalization) and tachycardia. straightforward diagnosis based on high levels of T4 in serum. treated with drugs that inhibit TH production followed by destroying or removing the dysfuncitonal thyroid gland. hyperthyroid may cause tachycardia severe enough to reduce cardiac output due to decreased filling time between cardiac contractions.

Methimazole (felimazole, tapazole)

antithyroid drug. interferes with incorporation of iodine in the molecule of T3 and T4. comes in tablets or topical gel for transdermal absorption. adverse effects include vomiting anorexia, hepatotoxicity, facial pruritus (causing self inflicted lesions on the face)

carbimazole (carbazole)

antithyroid drug used in europe for hyperthyroid

propranolol

beta adrenergic blocking agent used to suppress the tachycardia associated with hyperthyroidism.

radioactive iodine I131

sometimes used to destroy hyperactive thyroid tissue without destroying surrounding tissue. half life of 8 days, more than 99 percent of radiant energy will be gone in about 56 days. this method requires the patient to be housed in isolated facility for treatment for several days. the patients waste products require special disposal, most radioactive iodine is eliminated through urine.

Glucocorticoid hormones

play many roles in the body. The primary endogenous glucocorticoid is cortisol. Cortisol increases gluconeogenesis in the liver and inhibits glucose storage as glycogen, thereby increasing blood glucose. Cortisol also inhibits protein uptake by muscle, inhibits the, formation of bone and collagen, inhibits immune system functions, and affects the balance of water and electrolytes in the body. Glucocorticoids are released from the adrenal cortex in response to the release of ACTH from the anterior pituitary gland.

Adrenocortical insufficiency (Addison's disease)

a progressive condition associated with adrenal atrophy, usually caused by immune-mediated inflammation. Adrenal atrophy is not reversible, and it results in deficient production of glucocorticoids and mineralocorticoids. Signs of this disease are nonspecific and include lethargy, weakness, anorexia, vomiting, diarrhea, and PU/PD. diagnosed by the ACTH stimulation test, in which the ability of the adrenal cortex to respond to ACTH stimulation is tested by administering exogenous ACTH, then measuring blood cortisol levels. In healthy animals, ACTH stimulates additional cortisol release, while animals without a functioning adrenal cortex will have a blunted or absent cortisol response  to ACTH administration. ACTH is available as corticotropin (H.P. Acthar), an animal extract ACTH gel approved for veterinary use (which is currently not manufactured due to cost) or as cosyntropin (cortrosyn, synacthen), a synthetic form approved for use in humans (which is expensive and likely cost prohibitive for most owners). can also be diagnosed by measuring endogenous ACTH blood levels, which are elevated in primary hypoadrenocorticism because the hypothalamus senses the low levels of endogenous adrenocorticoid hormones in the blood and signals for the release of additional ACTH.

desoxycorticosterone pivalate (commonly referred to as DOCP) (Percorten-V", Zycortal

used for treatment of adrenocortical insufficiency. a long-acting mineralocorticoid approved for use in dogs. effective replacement for the endogenous mineralocorticoid hormone aldosterone and produces the same effects of retaining sodium and water in the body. DOCP is approved for administration by injection every 25 days, though the dosing interval may be adjusted based on the response of the patient. Adverse effects are uncommon and may include edema and electrolyte imbalance. Because of the effects on electrolyte balance, blood volume, and blood pressure, DOCP should be used with caution in animals with cardiovascular and renal disease. Many animals with adrenocortical insufficiency also require supplementation with a glucocorticoid drug; this is typically achieved by regular dosing with oral prednisone or prednisolone. Glucocorticoid effects and adverse effects, as well as other therapeutic uses

Fludrocortisone acetate (florinef)

a human-approved drug that is also used to treat adrenocortical insufficiency. a potent corticosteroid with both glucocorticoid and mineralocorticoid activity, but it has not been as effective as DOCP in the treatment of adrenocortical insufficiency. It is given once or twice daily by mouth. Adverse effects include edema and electrolyte imbalance.

latrogenic Addison's disease (hypoadrenocorticism)

occurs when glucocorticoid supplementation is abruptly discontinued instead of being tapered gradually, especially after high dosages are administered over long periods of time. Exogenous glucocorticoid administration triggers the negative feedback loop to greatly decrease endogenous corticoid production. Sudden withdrawal of exogenous glucocorticoid does not give the adrenal cortex-hypothalamus-anterior pituitary feedback loop time to readjust and increase corticoid quickly enough and in sufficient amounts to meet the body's needs, resulting in an Addisonian crisis.

Hyperadrenocorticism (Cushing's disease)

may be caused by adrenocortical tumors that produce excessive adrenocortical hormones or by pituitary disorders that cause excess ACTH production, leading to excess production of adrenocortical hormones. Animals with hyperadrenocorticism have signs of PU/PD, hair loss, and a pendulous abdomen due to abnormal protein metabolism. commonly diagnosed using urine cortisol levels and/or by a ow-dose dexamethasone suppression test. The low-dose dexamethasone test measures plasma cortisol concentrations before and at four and eight hours after IV administration of dexamethasone. If plasma cortisol levels are high eight hours after the administration of me exogenous corticosteroid dexamethasone, the normal negative feedback loop that limits production of endogenous adrenocortical hormones is not functioning, indicating the presence of hyperadrenocorticism. medical treatment of hyperadrenocorticism due to adrenocortical tumors is aimed at destroying part of the adrenal cortex or decreasing corticosteroid hormone production

latrogenic hyperadrenocorticism

may be caused by prolonged administration of excessive doses of glucocorticoid drugs, and it causes the same clinical signs as the naturally occurring condition. Hyperadrenocorticism is observed in dogs, horses, and, rarely, cats.

Mitotane o,p'-DDD (lysodren)

a human-approved drug that is cytotoxic to the adrenal cortex, by destroying the gland, it decreases hormone production. Adverse effects of mitotane use include neurologic signs  lethargy, vomiting, and diarrhea. Adverse effects are more common when there is a very rapid decrease in plasma cortisol levels: prednisone may be co-administered to reduce this risk. To prevent Gl adverse effects and to improve drug absorption, mitotane should be given with food.

Trilostane (Vetoryl

approved for use to decrease the production of adrenocortical hormone in dogs with adrenal tumors. It may also be used extra-label to treat pituitary dependent hyperadrenocorticism in dogs, hyperadrenocorticism in cats, and equine hyperadrenocerticism, which is also called equine cushing's disease or pituitary pars intermedia dysfunction (PPID). works at the level of the adrenal gland to block the production of cortisol, aldosterone, and androgens. This inhibition is reversible and dosage dependent. It is given once or twice daily with food. should be used with caution in animals with renal or hepatic disease. Adverse effects in dogs include lethargy, anorexia, or vomiting, which are usually transient. Because of the inhibition of aldosterone production, patients should be monitored for dehydration or electrolyte abnormalities. Dogs that cannot tolerate trilostane may be treated with ketoconazole, an antifungal drug that also blocks the enzymes needed to produce steroid compounds. Ketoconazole inhibits cortisol production; its effect on mineralocorticoid production is minimal. Adverse effects include vomit diarrhea, and hepatotoxicity. Ketoconazole should not be administered to pregnant animais as it can be teratogenic

pergolide mesylate (Prascend

FDA approved for the treatment of PPID in horses. FDA approved for the treatment of PPID in horses. stimulates dopamine receptors, which results in decreased secretion of ACTH from anterior pituitary gland. Anorexia is not uncommon at the start of therapy and may be managed By gradually increasing the dose at the onset of therapy. Adverse effect risks include weight loss, lethargy colic, diarrhea, and nervous system effects such as ataxia. This drug is not safe for use in dogs.

Proestrus

The period of the cycle before sexual receptivity. The corpus luteum (CL) regresses and progesterone levels decrease, permitting secretion of FSH by the anteriorpituitary gland. FSH stimulates follicular development and the release of estrogen, which helps prepare the reproductive tract for pregnancy.

Estrus

The period of the cycle in which the female is receptive to the male. FSH levels decrease and LH levels increase, causing the Graafian (dominant) follicle to rupture and release its egg (ovulation). Ovulation occurs during or shortly after estrus, depending on the species.

Metestrus

The period of the cycle after sexual receptivity. The CL forms in the ovary and produces progesterone, which suppresses ovulation and maintains pregnancy

Diestrus

If the animal is pregnant, the CL is fully functional and produces high levels of progesterone. If the animal is not pregnant, diestrus ends as the CL decreases in size in response to secretion of prostaglandin by the nongravid uterus

anestrus

A female animal that is not going through the estrous cycle. occurs before puberty and for a variable period after parturition. and it is a long phase between estrous cycles in seasonally polyestrous (e.g., sheep and horses) and monestrous animals (e.g., deer and wolves).

follicular phase

the stage of the estrous cycle in which the Graafian follicle is present; this includes proestrus and estrus. Estrogen is the predominant hormone

 luteal phase

 the stage of the estrous cycle in which the CL is present; this includes metestrus and diestrus. Progesterone is the predominant hormone

Androgens

male sex hormones produced in the testes, ovaries, and adrenal cortex. Most

testosterone, the primary male sex hormone, is synthesized in the interstitial cells (Leydig's cells

of the testes. Testosterone production is initiated and controlled by FSH and LH. Testosterone has both androgenic (promoting male characteristics) and anabolic (tissue-building) effects. In addition to maturation of the male sex organs and development of secondary male sex characteristics, testosterone helps spermatozoa develop and also helps develop and maintain accessory sex organs (like the prostate gland).

Testosterone (Synovex H, Component E-H with Tylan)

Testosterone, in combination with estradiol (a synthetic estrogen), with or without the antimicrobial drug tylosin, is FDA approved for use as an implant placed subcutaneously in the pinnae of cattle to improve growth rate

Boldenone (Equipoise

Anabolic steroids, synthetic steroidal drugs with anabolic effects (promotion of muscle growth), have androgenic effects similar to testosterone. It is approved for use in horses to improve weight, haircoat, and "general physical condition" in "debilitated horses".

Stanozolo/ (Winstrol-Va)

an anabolic steroid derived from testosterone and is approved for use in horses, dogs, and cats for its anabolic effects. Adverse effects of anabolic steroids are related to the androgenic activity and include increased aggressive behavior. The risk of hepatotoxicity from stanozolol is high in cats. Anabolic steroids are C-III controlled substances and are at high risk of abuse by humans for athletic performance and muscle-building effects. Due to abuse risks and the availability of approved appetite stimulants for dogs and cats, these products are not currently marketed in the United States.

Finasteride (proscar, propecia)

a human-approved inhibitor of an enzyme (5-alpha-reductase) that converts testosterone to dihydrotestosterone (DHT) in the prostate, liver, and skin. used orally in dogs to treat benign prostatic hyperplasia while preserving testosterone production and sperm quality. It has also been used in ferrets as an adjunctive treatment of hyperadrenocorticism. Adverse effects have not been reported in dogs.

estrogens

The ovaries, testes, adrenal cortex, and placenta produce estrogens. The ovarian follicle (the ovum and its encasing cells) and placenta in the female are the main sources of estrogen, a hormone that promotes female sex characteristics and stimulates and maintains the reproductive tract and accessory reproductive organs, including duct growth of the mammary glands. Estrogen stimulates female reproductive function and is necessary for the uterus to contract and respond to oxytocin. Estrogen also enhances such female secondary sex characteristics as mammary development, plumage, and beak color

estriol (Incurin

A synthetic estrogen is FDA approved for the treatment of estrogen-responsive Incontinence in dogs; this condition occasionally occurs as urine leakage in ovariohysterectomized bitches The drug may also be used extra-label for estrogen-responsive dermatosis in ovariohysterectomized bitches. Adverse effects include anorexia, vomiting, and estrogenic effects such as a swollen vulva, mammary hyperplasia, and behavioral changes

Progesterone Drugs (The "Gest"s)

progesterone is a female sex hormone produced and secreted by the CL, an ovarian structure at develops after ovulation. Progesterone decreases uterine activity when a female is pregnant, d it is important for the maintenance of pregnancy in most veterinary species. Progesterone inhibits estrus and ovulation.

Medroxyprogesterone acetate (depo-provera, provera, cycrin)

a human-approved drug that may be administered orally or by injection for the treatment of noninflammatory alopecia in dogs. It has also been used to prevent estrus in horses that are competing in sporting events, but this effect has not been proven by research, and the drug is banned for use in equine competitions in Canada. It has been used to treat urine spraying in cats, but this use is not recommended due to the high risk of adverse effects in cats, including adrenocortical suppression and DM. Other adverse effect risks include polyphagia, PU/PD, and mammary hyperplasia.

Altrenogest (Regu-Mate, Altren,  OvaMed)

FDA approved for use in mares to suppress estrus and for use in estrus synchronization protocols, and it may be used extra-label in low dosages to maintain pregnancy in mares (Figure 10-20A). When a progesterone drug is administered for days to weeks and then stopped, GnRH release is stimulated, and the animal will cycle again. Adverse effects are uncommon in species other than cats. Altrenogest can be absorbed through the skin and should not be handled by pregnant women.

Matrix, ChronoMate, SwineMate

used to synchronize estrus in young swine using several FDA-approved products that are administered in feed

Progesterone (Eazi-Breed CIDR

cattle insert or sheep insert progesterone is marketed in the United States. This intravaginal insert has progesterone in elastic rubber molded over a nylon spine is inserted with a special applicator into the vagina. The insert is placed in the cranial portion of the vagina for seven days and then removed. Progesterone is absorbed from the insert through the mucous membranes of the vagina. Similarly to the use of altrenogest, administration. Over days to weeks followed by discontinuation of administration (by removal of the insert) results in estrus within a few days in most treated animals. In cows, prostaglandins and GnRH are used in combination with progesterone-containing inserts in estrus-synchronization protocols to improve e likelihood of successful synchronization and make the timing of the resulting estrus more predictable. Intravaginal inserts may cause irritation to vaginal tissues that generally resolves after removal of the insert. Gloves should be worn when handling inserts to prevent transdermal absorption of progesterone.

(Synovex-c, Synovex-S, Component M E-C with Tylan, Component E-S with Tylan

Progesterone is also included with estradiol with or without the antimicrobial drug tylosin in some growth-promoting implants for subcutaneous use in cattle

Melengestrol acetate or MGA

included in more than 30 FDA-approved products fed to cattle. This synthetic form of progesterone is used to suppress estrus, promote growth, and improve feed efficiency in feedlot heifers. Heifers are fed this supplement daily to improve weight gain and feed efficiency and suppress estrus. This supplement is not effective in steers. These fed products often combine MGA with other growth-promoting, antiparasitic, and antimicrobial drugs.

Prostaglandin Drugs (The "Prost"s)

Many groups of prostaglandins occur naturally in the body (groups include A, B, C, D, E, and E and prostaglandins are made by almost every cell in the body. Prostaglandin F2. (PGF2„) is made in the uterus. A nonpregnant uterus releases prostaglandin F2,, during diestrus, which cause lysis of the CL. The lysed CL discontinues secretion of progesterone, and lower progesterone levels permit ovulation and the initiation of a new estrous cycle. PGF2,, also causes contraction of smooth muscle, including uterine muscle, which may facilitate expulsion of pus in pyometra or a fetus in cases of fetal death or incomplete abortion. In cattle, PGF2, is used in estrus synchronization protocols. When PGF, is given to cattle in diestrus, it will lyse the CL, and cows with active CLs at the time of treatment will experience estrus two to four days later. In small animals, PGF. is used to treat pyometra, cause abortion, and induce parturition; it may also be used to induce parturition in sows. In mares, it is used for estrus synchronization. Pregnant women should not handle prostaglandins, as they can be absorbed through the skin and can cause uterine contractions. Other adverse effects are due to smooth muscle contraction and include bronchoconstriction and elevated blood pressure in animals and humans. Because of the risk of bronchial constriction, people with asthma should not handle prostaglandins. Examples of prostaglandins include dinoprost tromethamine (Lutalyse which is approved for use in mares, sows, and cows, and cloprostenol sodium (Estrumate, estroPLAN which is approved for use in cows

Gonadotropins (Gonadal Hormone-Production Stimulators)

 hormones that stimulate the gonads to release LH and FSH. LH activity is simulated with the use of human chorionic gonadotropin (hCG), FSH activity is simulated by pregnant mare serum gonadotropin (PMSG), and GnRH is synthetically prepared. Gonadorelin or GnRH is produced in healthy animals by the hypothalamus. GnRH causes release of FSH and LH by the anterior pituitary gland; this ultimately produces ovulation. GnRH is FDA approved for use by injection to treat follicular cysts and for estrus synchronization in cattle. GnRH is an important component of bovine estrus synchronization protocols for fixed-time artificial insemination, in which observation of behavioral estrus is not necessary. Gnkn has been used extra-label in protocols to induce estrus in small animals, but the efficacy of these indications is not well established, Adverse effects are rare. Examples of GnRH are Cystorelin, OvaCyst, Fertagyl, Factrel and GONAbreed

Improvest

a combination of gonadotropin-releasing factor with a diphtheria toxoid, which

stimulates a response in the immune system of male pigs against their own endogenous gonadotropin-releasing factor After the second dose, this drug reduces testicular function, including fertility and "boar taint" (meat with a flavor associated with intact male swine). This drug should not be handled by pregnant women as it may interfere with maintenance of the pregnancy. It should be handled carefully by men and women of childbearing age

hCG (Chorulon

has the same ovulation-stimulating effect as LH. It is FDA approved for the treatment of cystic ovaries in cattle and to improve reproductive performance in finned fish. Pregnant mare serum gonadotropin PMSG acts like naturally occurring FSH. PMSG and chorionic gonadotropin are combined in the FDA-approved product P.G.6003, which is used to induce estrus in gilts and sows. Because chorionic gonadotropin is a protein, there is a risk of anaphylaxis after administration; this is treated with the administration of epinephrine.

Growth promotants

anabolic agents that help increase the efficiency of weight gain in animals. implants have been used since the 1940s to increase feed efficiency And weight gain in beet cattle and sheep. Implants are small pellets (about the size of a sunflower seed) placed under the skin at the caudal aspect of the pinna of livestock. This placement reduces the possibility of hormone residues in human food products because the pinnae of cattle are removed at slaughter and not used in the production of human food. Each pellet contains a growth-promoting hormone that is slowly released into the blood and is subsequently carried to tissues. When growth-promoting implants are placed in the pinna, there is a rapid release of hormone from the implant. The level of growth-promoting hormone will begin to fall a few days after implantation, but it remains above the animal's normal level for a varying length of time, depending on the type of implant and the drug in the implant. Growth promotants must be approved by the FDA in the United States and are subject to local regulation. Many implants contain small amounts of antibiotic drug to prevent infection at the site of administration. Adverse effects of growth promotants that are synthetic hormones include mounting behavior, rectal prolapse, ventral edema, and udder development. Most growth promotants should not be given to dairy cattle or breeding animals. There are many brands and combinations of implants on the market.

Estradiol

 a form of estrogen. It is a potent anabolic agent in ruminants and is administered either as a compressed-tablet implant or an impregnated-rubber implant. Estradiol given to steers increases growth rate by 10 to 20 percent, lean meat content by 1 to 3 percent, and feed efficiency by 5 to 8 percent. Estradiol is not an effective anabolic agent in pigs. It is a component of numerous implant products, usually in combination with other hormones such as progesterone, testosterone, or trenbolone

trenbolone acetate (TBA) (Revalor

synthetic hormone used to promote growth in feedlot heifers, calves, and sheep. It works like testosterone but with greater anabolic activity. Unlike natural testosterone, TBA works by itself and when combined with estradiol as a pellet-type implant in heifers and cull cows. It is not intended for use in breeding or dairy animals. synthetic hormones tend to be more potent than naturally occurring ones

zeranol (Ralgro

which is an analog of a naturally occurring plant estrogen and is used as a subcutaneous ear implant to enhance weight gain and feed efficiency in cattle and sheep