Clinical uses of Reproductive Hormones

The use of hormones is a major component of  theriogenology. Hormone preparations are utilized as reproductive management  tools, diagnostic aids and therapeutic agents. The effective use of hormones in theriogenology requires knowledge of both normal reproductive endocrinology and the therapeutic characteristics of available  hormonal preparations.

Gonadotropin Releasing Hormones (GnRH)

GnRH is produced by the neurons of the hypothalamus. The application of GnRH and its analogues in Theriogenology is based on their ability to stimulate release of FSH and LH from the anterior pituitary following a single injection.

Indications

Cattle 

used primarily in the treatment of ovarian follicular cysts.

delayed ovulation or anovulation.

Acyclicity

Improve pregnancy rates, and the chances of conception in cyclic non-breeders

Oestrus synchronisation

Horse 

Induction of ovulation, single injection may not be effective requires frequent repeated doses. 

Dose

Cow: 0.25- 0.5 mg 

Sheep and goat: 0.1 mg

FSH

Indications:

Cattle:

Superovulation of donor cows for embryo transfer

Treat anestrous

 treat bulls with impaired spermatogenesis and enhance descent of the testicle in  cryptorchids is questionable.

Sheep and Goats:

Association with intravaginal progestoren sponges to advance the onset of the breeding season. (Superovulation).

Dose:

1Cattle: 1500-3000 I.U.

2 Sheep and Goats: 500-600 I.U.

LH

Indications:

-used to bring about ovulation

- used in treating cows with ovarian follicular cysts. (Nymphomania).

- produces temporary stimulation of the interstitial cells of the testicles to produce 

testosterone resulting in an increase in libido.

- used to increase the size of the corpus luteum and increase the amount of progesterone when administered four days after ovulation has occurred.

Dose:

1-Cattle: 1500-3000 I.U.

2-Sheep and Goats: 500-600 I.U.

Oxytocin

Indications:

Cattle

1. Induces milk let-down in heifers and in cows with mastitis.

2. Hastens uterine involution following dystocia, caesarean operation, and replacement of uterine prolapse, uterine trauma or hemorrhage.

Horses

1. Drug of choice for the induction of parturition 

2. Causes expulsion of the fetal membrane

3. Induces milk let-down

Dose:

1-Cattle: 50-100 I.U.

2-Sheep and Goats: 40 I.U.

Oestrogen

Indications

1. They are used to evacuate the uterus in cases of fetal mummification, fetal maceration 

and pyometra.

2. They are used to induce abortion in all species.

3. They can be used in the treatment of postpartum metritis and retained fetal 

membranes.

4. Used in the management of misalliance in dogs.

5. To produce signs of estrus in anestrual animals. (no ovulation)

6. In virgin heifers and dry cows estrogen can be used to stimulate mammary development 

and lactation.

7. Large doses of estrogen after parturition can be used to inhibit lactation and relieve 

congestion of the mammary glands.

8. Used as growth promotants in beef cattle.

9. In treating male dogs with prostatic hyperplasia.

10. Can be used to decrease libido in males.

Side Effects

1. Prolonged use or large doses can produce cystic ovaries or ovarian atrophy.

2. Because of its effect on the ligaments, the estrogens predispose to prolapse of the vagina and rectum and dislocations and fractures of the pelvic bones.

3-In some species the estrogens in combination with progesterone may increase the incidence of cystic endometrial hyperplasia –pyometra.

Dose:

Cattle: 4-6 mg

Sheep and Goats: 2-3 mg

Progesterons (Progestins)

Prevent abortion due to an actual or possible progesterone deficiency

Estrum deferment or suppression in the ewe, cow, sow, mare and bitch.

Synchronization of estrus in the mare, ewe, cow and sow

In heifers the progestins are used to promote growth suppresses heat

Dose:

Cattle: 125 mg

Sheep and Goats: 40 mg

Prostaglandins

Uses

Mares:

treatment of prolonged diestrus (persistence of the CL)

to shorten diestrus.

breeding after foal heat

in the evaluation and treatment of endometritis

Cow and Ewe:

1. evacuation of the uterus (mummified,pyometra,endometritis).

2. synchronization of estrus.

3. induce abortion in heifers and ewes that are mated too young.

4. induction of early parturition in cows, e.g. in cases of uterine fetal oversize.

5. Treatment of luteal cysts

Note:

1. Prostaglandin F2 alpha should only be given to pregnant animals if abortion is desired.

2. PGF2 alpha should not be administered by the intravenous route.

3. Contact with the skin should be avoided. 

Dose:

Cattle: 15-25 mg

Sheep and Goats: 7.5-10 mg

Placental hormones

Pregnant mare serum gonadotropin (PMSG) now called equine chorionic gonadotropin (eCG).

A protein hormone produced by the endometrial cups of the mare from about 40 to 140 days of pregnancy. It contains both FSH and LH, but its activity is mainly FSH.

Indications:

Cattle:

Superovulation of donor cows for embryo transfer.

Sheep and goats:

Association with intra vaginal sponges. 

Dose:

Cattle: 1500-3000 I.U.

Sheep and Goats: 500-800 I.U.

Human chorionic gonadotropin (hCG)

A protien hormones Produced by chorionic epithelial cells of human placentae. It is 

excreted in the urine and reaches peak levels at about 50 days of pregnancy. Its activity is 

predominantly LH, it also has a longer half –life than LH.

Human menopausal gonadotropin (hMG)

Extracted from the urine of menopausal women, this has primarily an FSH-like action. 

Used to a limited extent in superovulating donor cows for embryo transfer. It has a shorter 

biological half-life than eCG.

Melatonin

Melatonin hormones produced by the Pineal gland. Level of secretion depend on photoperiod, 

Increasing day length inhibiting 

Decreasing day length stimulating