Female reproductive hormones

Hormones:

Hormones are molecules that function as a message carrier within an organism, its only function is to convey information. Hormones are chemical agents which are carried by the blood to cells within a target organ of other target cells where they regulate a specific physiological activity.

The hypothalamus secretes releasing hormones which influence the release of gonadotrophins from the anterior pituitary (adenohypophysis).

Hypothalamus:

Release hormones

The following are the releasing hormones secreted by the Hypothalamus:

Gonadotrophin releasing hormone (GnRH 

1.Thyrotrophic releasing hormone (TRH) 

2.Prolactin releasing factor (PRF)

3.Prolactin inhibiting factor (PIF)

Anterior pituitary gland

1.FSH

2.LH

3.Prolactin

Origin and roles of female reproductive hormones

Gonadotropin Releasing Hormone (GnRH) 

Origin:

Hypothalamus 

Role in female reproduction:

Stimulate anterior pituiitary gland  to produce Follicle Stimulating Hormone (FSH) and Leutinising Hormone (LH) from the anterior pituitary gland 

Leutinising hormone

Origin:

Anterior pituitary gland

Roles in female reproduction:

 LH stimulates the production of 

    oestrogens and progesterone from the ovary via 

     theca interna cells and luteal cells 

Follicle Stimulating Hormone (FSH)

Origin:

Anterior pituitary gland

Roles in female reproduction:

 FSH stimulates the maturation of germ cells within gonads

 In female-stimulates follicular development and oestradiol synthesis 

In male FSH also stimulates the secretion of inhibin which has a negative feedback directly to the anterior pituitary 

Prolactin (PRL)

Origin:

Anterior pituitary via lactotroph cells

Roles in female reproduction:

A stimulatory effect on milk synthesis within the mammary glands

Brudiness in mother

STEROIDS OESTROGENS e.g. Oestradiol 

Origin: 

Ovary via granulosa cells,Placenta and the adrenal cortex. 

Roles in female reproduction:

Prepare the external genitalia for copulation

Helps in development of fertilised egg cells

Contribute to the growth and development of mammary tissue

Prepare the uterus for parturition.

PROGESTINS e.g. Progesterone

Origin:

Corpus luteum and the placenta 

Roles in female reproduction:

i. Inhibition of sexual behavior.

ii. Maintenance of pregnancy via inhibition of

uterine contractions and promotion of glandular development in the endometrium.

iii. Promotion of alveolar development of the

mammary gland.

iv. Synergizes with oestrogen to prepare the

uterus for pregnancy mammary gland for lactation.

v. Regulates the release of GnRH via negative feedback control. 

NON-STEROIDS OXYTOCIN 

Origin:

Neurohypophysis 

Roles in female reproduction:

i. Stimulates the contraction of smooth muscle in the oviduct and uterus during parturition.

ii. Elicits milk ejection reflex by stimulating the myoepithelial cells of the mammary gland.

iii. It aids in sperm transport

iv. It helps in ovum transport 

PROSTAGLANDIN –

Origin:

found in the follicular

fluid of Graafian follicles

prior to ovulation e.g.

PGF and PGE are the 2

most important for

reproduction

Prostaglandin F2α

uterine endometrium and vesicular glands

Target organ: female is the corpus luteum, uterine myometrium and                                 ovulatory follicles 

Roles in female reproduction:

 luteolysis: Causes regression of the corpus luteum 

 Helps in ovulation 

 Induction of uterine tone and contractions

Stimulates the smooth muscles of the

genitalia. 

Prostaglandin (PGE2)

PGE2 is another form of prostaglandin that is produced by the ovary, uterus and embryonic membranes

Vasodilation, Smooth muscle relaxation, and

Inhibition of the release of noradrenaline from sympathetic nerve terminals during labour where it aids the softening of the cervix

Inhibin 

Origin:

a protein

hormone produced by the

granulosa cells of the

ovarian follicle

granulosa cells and

placenta.

Roles in female reproduction:

It suppresses the release of FSH from the anterior

pituitary. 

Melatonin 

Origin:

Produced by the pineal gland.

Its secretion is coupled to

daylight i.e. decreased daylight

stimulates its release 

Roles in female reproduction:

 It is relevant in the seasonal breeders e.g. Ewe, Queen etc.

It decreases reproductive activity in most species

associated with decreased production of oestrogen and

other reproductive hormones from the ovary and with an increased refractory time after mating before a subsequent mating occurs. 

Equine chorionic Gonadotrophic  hormone (eCG) =PMSG 

Origin:

Produced by uterus and placenta 

Roles in female reproduction:

 i. Stimulation of follicular growth.

ii. Stimulation of super ovulation in embryo transfer.