The document provides an overview of hormones, their classifications based on source and mode of action, and their clinical applications in reproductive medicine. Key classifications include hypothalamic, pituitary, gonadal, and placental hormones, as well as various types of hormones based on their functions, such as neurohormones and sexual promoters. Clinical uses of reproductive hormones are discussed, detailing their roles in managing fertility, synchronizing estrus, and supporting pregnancy in animals.

1. Hormones
Substance produced by a gland that acts on a remote tissue (target
tissue) to bring about a change in the target tissue.
Changes may involve alterations in metabolism, synthetic activity and
secretory activity.
In blood, level of hormones ranges from nanograms to picograms per
ml.
Classification:
1. Source (origin)
2. Mode of Action

2. Classification on the basis of Source (origin)
1. Hypothalamic Hormones: produced by neurons in the
hypothalamus. They cause the release of other hormones from anterior
lobe of the pituitary. For example, gonadotropin releasing hormone
(GnRH).
2. Pituitary Hormones: are released into blood from the anterior and
posterior lobes of pituitary.
• Anterior lobe…...Follicle Stimulating Hormone (FSH), Luteinizing
hormone (LH) and prolactin.
• Posterior lobe….. Oxytocin

3. Classification on the basis of Source (origin)
3. Gonadal Hormones: originate from gonads and affect function of the
hypothalamus, anterior lobe of PG and tissue of reproductive tract.
Gonadal hormones also initiate the development of secondary sex
characters that cause “maleness or femaleness”
• Ovary: estrogens, progesterone, inhibin, some testosterone, oxytocin
and relaxin.
• Testes: Testosterone, inhibin and some estrogen.
4. Uterus: Prostaglandin PGF2α
5. Placental Hormones: Progesterone, estrogen, equine chorionic
gonadotropin (eCG) and human chorionic gonadotropin (hCG).

4. Classification on the basis of Mode of Action
1. Neurohormones: are synthesized by neurons and release directly into blood
so that they can cause a response in target tissue elsewhere in the body. For
example oxytocin.
2. Releasing Hormones : are synthesized by neurons in the hypothalamus and
cause release of other hormones from anterior lobe of pituitary. For Example
GnRH.
3. Gondotropins: are hormones released by gonadotrophs cells of the anterior
lobe of pituitary and they stimulate the gonads. For Example FSH, LH.
4. Pregnancy maintenance Hormone: Progesterone
5. Lactogenic Hormones: placental lactogen promotes development of
mammary gland of dam for example prolactin.

5. Classification on the basis of Mode of Action
6. Sexual promoters Hormones: are produced by the gonads of the
both the male and female for example estrogen, progesterone and
testosterone.
• Stimulate the reproductive tract
• To regulate the function of hypothalamus and the anterior lobe of
pituitary
• To regulate the reproductive behavior
• Involve in secondary sex characters
• Sexual promoters are driving force for all reproductive functions

6. Classification on the basis of Mode of Action
7. Luteolytic Hormone: causes the destruction of corpus luteum. for
example PGF 2α.
8. General Metabolic Hormones:
• Thyroxin……. Regulates the metabolic rate of animal.
• Adrenal Corticoids….. Mineral metabolism to regulation of
inflammatory responses.
• Growth hormones (somatotropin)….. Regulate the growth, lactation
and protein metabolism.

7. Clinical Usage of reproductive Hormones
• GnRH (GONADOTROPHIN RELEASING HORMONE)
• a) For the treatment of follicular cysts
• b) For the treatment of delayed ovulation or anovulation
• c) For improved in pregnancy rates, in cows with poor pregnancy rates, when used as ‘holding
injection’ as a single bolus 12 days after insemination
• d) In oestrus–synchronisation regimens.
• Commercially available Products: Buserelin, delmaraline.
• 2. Gonadotrophins
• FSH ( Follicle stimulating hormone).
• a) Superovulation of donor cows for embryo transfer
• b) impaired spermatogenesis in bulls
• c) Used to treat acyclicity

8. • Equine chorionic gonadotrophin (eCG). Originally called pregnant mare’s serum
gonadotrophin (PMSG) but in order to use consistent nomenclature it is now called
eCG. A protein hormone produced by the endometrial cups of the mare from about 40–
120 days of pregnancy. It mainly has FSH-like activity but with a much longer biological
half-life than FSH.
• Commercially available products eCG or serum gonadotrophin Folligon, Fostim.
• LH ( Luteinizing hormone)
• a) For the treatment of delayed ovulation or anovulation
• b) For the treatment of ovarian cysts (especially follicular)
• c) To treat luteal deficiency
• d) improve chances of pregnancy in cyclic non breeders (repeat breeder cows).
• e) improve libido in bull
• Human chorionic gonadotrophin (hCG). A protein hormone extracted from the urine
of pregnant women, this hormone has primarily an LH-like effect and hence is used as a
substitute for the more expensive LH, it also has a longer half-life than LH.
• Commercially available products, Chorulon injection.

10. • Oxytocin:
• a) induce milk letdown
• b) hasten uterine involution following dystocia, caesarean operation,
after replacement of uterine prolapse, uterine trauma or haemorrhage.
• c) cause expulsion of retained fetal membranes
• d) Used for the treatment of uterine inertia
• Commercially available products Oxytocin, Hyposton
• 4. Oestrogen:
• a) treatment of endometritis
• b) prevention of unplanned pregnancy
• c) depress hypersexuality in the male dog.
• Commercially available products, Oestradiol benzoate, Diethylstilboestrol

11. • Progesteron:
• a) Used for synchronisation of oestrus.
• b) to induced ovulation in cows and heifers in conjunction with prostaglandin F2α (PGF2α)
• c) treatment of acyclicity (true anoestrus) in cows and heifers
• d) treatment of non-observed oestrus in cows.
• e) To maintained pregnancy
• Commercially available product, PRID ( 1.55gm) inserted for 12 days and at the day of
removal 1 injection of PGF2α, CIDR ( 1.9gm) inserted for 7-12 days with PGF2α at the time
of removal.
• 6. Androgen:
• a) To increase the libido in male
• b) Has anabolic effect so used for treatment of debilitated animals
• c) Used for spermatogenesis
• Commercially available products Methyltestosterone tablets, Testosterone esters injection.
• Androgen have limited application in animal reproduction or disease

12. • Prostaglandins:
• a) Synchronization of oestrus in cow and heifers
• b) Treatment of non-observed oestrus
• c) Induction of calving
• d) Inducing abortion and expulsion of mummified calves
• e) Treatment of pyometra
• f) Treatment of endometritis
• g) Treatment of luteal (luteinised) cysts.
• Commercially available products, Estrumate, Lutalyse, Delmazine.
• Melatonin: produced by the pineal gland. Its level of secretion is influenced by the
photoperiod, with reducing day length stimulating and increasing day length inhibiting its
secretion. Melatonin modulates, either directly or indirectly the frequency of GnRH
secretion from the hypothalamus, thus influencing the secretion of gonadotrophins and
cyclical ovarian activity.
• Commercially available products, Melatonin implant.
• Indications: Advancing the onset of normal cyclical ovarian activity in pure and cross-bred
breeds of sheep so that early lambing occurs.