This presentation describes the role of hypothalamus on Adenohypophysis reproductive hormones. Also you will be learned about the functions of reproductive hormone released by anterior pituitary.

1. Hypothalamus control on
Adenohypophysis
reproductive hormone
Presented by : Praddum Namdev
En No. 2001218005
MSc zoology 3rd sem
IGNTU AMARKANTAK MP

2. • Overview
• Hypothalamus
• Anterior pituitary
• Reproductive functions of anterior pituitary
• Gonadotrophs, structure function & secretion
• Stimulation of gonadotrophs
• LH & FSH

3. Hypothalamus control of reproductive
hormone from Adenohypophysis
• Most important hormone for reproduction is called Gonadotropin
releasing hormone (GnRH) released in a rhythmic fashion every 60
to 120 minutes.
• Puberty is initiated by gonadotropin-releasing hormone (GnRH), a
hormone produced and secreted by the hypothalamus.
• GnRH stimulates the anterior pituitary to secrete gonadotropins—
hormones that regulate the function of the gonads.
• the levels of GnRH are regulated through a negative feedback loop;
high levels of reproductive hormones inhibit the release of GnRH.
• In males throughout life, gonadotropins regulate reproductive
function and, in the case of women, the onset and cessation of
reproductive capacity.

4. Hypothalamus
• Highly involved in pituitary gland function.
• When it receives a signal from the nervous system, the hypothalamus
secretes substances known as neurohormones that stimulates or
inhibit the secretion of pituitary hormones.
• The hypothalamus–pituitary complex can be thought of as the
“command center” of the endocrine system.
• This complex secretes several hormones that directly produce
responses in target tissues, as well as hormones that regulate the
synthesis and secretion of hormones of other glands.
• The hypothalamus–pituitary complex coordinates the messages of the
endocrine and nervous systems.
• Stimulus received by the nervous system must pass through the
hypothalamus–pituitary complex to be translated into hormones that
can initiate a response.

5. Anterior pituitary-(adenohypophysis)
• 1. Originates from the digestive tract in the embryo and
migrates towards the brain during fetal development.
• 2. there are three regions:
A. pars distalis is the most anterior,
B. pars intermedia, adjacent to posterior pituitary.
C. pars tuberalis is a slender “tube” wraps the infundibulum.
3. Anterior pituitary does manufacture hormones however,
the secretion of hormones from the anterior pituitary is
regulated by two classes of hormones secreted by
hypothalamus—
A. Releasing hormones (GnRH)
B. Inhibiting hormones (Somatostatin)

7. Reproductive functions of the
anterior pituitary:
• Gonadotrophs:
1. Specialized cell types of the anterior pituitary that synthesize
and secrete LH and FSH.
2. Constitute 7% to 15% of the total number of anterior pituitary
cells and are detected in this location from early fetal life.
3. Most gonadotrophs are capable of synthesizing both LH and
FSH.
4. LH and FSH are each composed of two distinct, noncovalently
associated protein subunits called α and β.
5. In the gonadotroph, the subunit genes are transcribed into
messenger ribonucleic acids (mRNAs), which are translated
into the subunit precursors.

8. • How GnRH work-
• Gonadotrophs contain cell surface GnRH type 1 receptors that
mediate the action of GnRH.
• These receptors belong to the seven-transmembrane
domain and G protein– coupled receptor family.
• The “reproductive system” includes the complex
hypothalamus-pituitary-gonad (HPG) axis as well as the
targets of steroid hormones secreted by the gonads.
• Hypothalamus – GnRH
• Adenohypophysis- gonadotropin – FSH & LH
• Neurohypophysis – Oxytocin

9. Gonadotrophs; Structure, Function &
Secretion
• Also called- Gonadotropic cells or Gonadotrophs or Delta Cells or Delta
basophils) are endocrine cells
• In the anterior pituitary Gonadotrophs are found throughout the anterior
pituitary, alone or in groups, often in close contact with blood capillaries.
• They are oval in shape with prominent, often eccentrically located, nuclei.
• They have RER, Golgi complexes and many secretory granules, that stain
strongly for both LH and FSH.
• gonadotrophs express
– Cga gene- alpha glycoprotein subunit,
– Fshb and Lhb- Beta subunit of gonadotrophs
– gonadotrophs are defined by two other genes not expressed in other secretory
pituitary cell types:
– The GnRH receptor (GnRHR)
– Gene (Gnrhr)
– Dentin matrix protein 1 gene .

10. • The gonadotrophs also secrete other soluble
proteins, including chromogranins and
secretogranins.
• Morphologically, gonadotrophs contain two
types of secretory granules:
• Small granules containing secretogranin II
• Large granules containing chromogranin A.

11. Stimulation of Gonadotropic Cells-
• Gonadotropin releasing hormone (GnRH) is secreted from the hypothalamus
and stimulates gonadotropic cells in the anterior pituitary gland to release
luteinizing hormone and follicle-stimulating hormone, which in turn regulate
the gametogenic and steroidogenic functions of the gonads in male and
female.
• Gonadotrophs are excitable cells- They express numerous voltage-gated
channels;
– sodium (Nav),
– calcium (Cav),
– potassium (Kv), and
– chloride (Clv) channels at the plasma membrane that fire spontaneous action
potentials .
• Gonadotrophs also express ligand-gated ion channels, and their activation by
hypothalamic or intrapituitary ligands causes increased firing frequency and
facilitates Ca 2+ influx and hormone release.
• The main Ca 2+-mobilizing receptor is GnRHR.

12. • Two Hormones-
• FSH Follicle stimulating hormone
• LH ( Luteinizing hormone )
• Follicle-stimulating hormone (FSH)- stimulates the
production and maturation of sex cells, or gametes,
including ova in women and sperm in men.
• FSH also promotes follicular growth- estrogens in the
female ovaries.
• Luteinizing hormone (LH)- triggers ovulation in women, as
well as the production of estrogens and progesterone by
the ovaries.
• LH stimulates production of testosterone by the male
testes.