This document summarizes pituitary and hypothalamic hormones. It describes how the hypothalamus regulates the anterior pituitary through releasing factors. The anterior pituitary then regulates other endocrine glands through six main hormones: growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, follicle stimulating hormone, luteinizing hormone, and prolactin. The posterior pituitary secretes oxytocin and antidiuretic hormone. Each hormone's structure, function, and role in feedback loops controlling hormone release is summarized.

1. PITUITARY AND HYPOTHALAMIC
HORMONES
PRESENTED BY
BHARATHI N
II MSc BIOCHEMISTRY
ISLAMIAH COLLLEGE (AUTONOMOUS)
VANIYAMBADI.

2. HYPOTHLAMUS :
• Hypothalamus is a specialized center in the brain that
function as a master coordinator of hormonal action.
• In response to the stimuli of central nervous system,
hypothalamus liberates certain releasing factors or
hormones.
• These factors stimulate or inhibit the release of
corresponding tropic hormone form anterior pituitary.
• In general the hormonal system is under feedback
control , for instance adrenocorticotropic hormone
(ACTH) inhibits the release of corticotropin releasing
hormone (CRH).

3. HYPOTHALAMIC HORMONES :
• The anterior pituitary under control of hypothalamic
hormones.
• Hypothalamic produces six releasing factors or
hormones, they are given below,
• Thyrotropin releasing hormone (TRH)
• Corticotropin –releasing hormone(CRH)
• Gonadotropin –releasing hormone(GnRH)
• Growth hormone –releasing hormone(GRH)
• Growth hormone release-inhibiting hormone (GRIH)
• Prolactin release –inhibiting hormone (PRIH)

4. 1)Thyrotropin releasing hormone:
• It is a tripeptide consisting of glutamate derivative
(pyroglutamate),histidine , proline.
• (Pyro)glu-His-Pro-NH2
• TRH stimulates anterior pituitary to release thyroid
stimulating hormone (TSH or thyrotropin) which in turn ,
stimulates the release of thyroid hormone ( T3 and T4 ).
• TRH suggest that a calcium-phosphatidyl inositol mechanism.

5. 2)Corticotropin releasing hormone
(CRH):
• CRH contains single chain of 41 amino acids.
• It stimulate anterior pituitary to release
adrenocorticotropic hormone (ACTH) which is
turn, acts as adrenal cortex to liberate
adrenocorticosteroids.
• Adrenocorticosteroids hormones they are given
below
• Glucocorticoid hormone
• Mineralocorticoids
• Androgens and estrogen.

6. 3)Gonadotropin releasing hormone
(GnRH) :
• GnRH is a deca peptide .
• (pyro) Gly-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-
Gly-Gly-NH2
• GnRH stimulates anterior pituitary to release
gonadotropins, namely luteinizing hormone(LH) and
follicle stimulating hormone(FSH).
• GnRH suggest that a calcium-phosphatidyl inositol
mechanism.

7. 4)Growth hormone releasing hormone
(GHRH) :
• Growth hormone releasing hormone (GHRH)
is made up single chain of 44 amino acids .
• GHRH is stimulates the release of growth
hormone (GH or somatotropin ) which
promotes growth.

8. 5)Growth hormone release inhibiting
hormone (GRIH) :
• GRIH is contains single chain of 14 amino
acids.
• Ala-Gly-Cys-Lys-Asn-Phe-Phe-Trp-Lys-Thr-Phe-
Thr-Ser-Cys-NH2.
• GRIH is also known as somatostatin.
• GRIH inhibiting the release of growth
hormone from the anterior pituitary.

9. 6)Plolactin release inhibiting hormone
(PRIH):
• PRIH is believed to be a dopamine and or a
small peptide .
• PRIH inhibits the release of prolactin (PRL)
from anterior pituitary .

10. Relationship between hypothalamic
hormones and pituitary hormones

11. Pituitary hormones :
• The pituitary gland or hypothesis (weighing
about 1g) is located below the hypothalamus
of the brain.
• It consists of two distinct parts the anterior
pituitary (adenohypophysis) and the posterior
pituitary (neurohypophysis).

12. Anterior pituitary hormone
1. Growth hormone (GH)
2. Thyroid stimulating hormone (TSH)
3. Adrenocorticotropic hormone (ACTH)
4. Follicle stimulating hormone (FSH)
5. Luteinizing hormone (LH)
6. Prolactin (PRP)

13. Posterior pituitary
1. Antidiuretic hormone (ADH)
2. Oxytocin

14. Pituitary hormone

15. Anterior pituitary hormones :
• Anterior pituitary or adenohypophysis is truly the
master endocrine organ.
• It produce several hormone that influence either
directly or indirectly a variety of biochemical processes
in the body.
• The hormone of adenohypophysis are broadly
classified into three categories.
1. The growth hormone –prolactin group.
2. The glycoprotein hormone .
3. The pro-opiomelanocortin (POMC) peptide family.

16. A)The growth hormone-prolactin
group:
• Growth hormone (GH), prolactin (PRL)
chorionic somatomammotropin (CS; placental
lactogen ) are protein hormones with many
striking similarities in their structure.
• A)Growth hormone (GH): The growth
hormone (or somatotropin ) is produced by
somatotropes , a special group of acidophilic
cells of anterior pituitary .

17. • GH is a single polypeptide with a molecular
mass of about 22kDa in all mammalian
species.
• The general structure of the 191 amino acid.
• The structures of human growth hormone has
disulfide bonds between residues 53-165 ad
182-189.
Structure of growth hormone (GH):

18. Biochemical function of GH :
• Growth hormone promotes growth, and also
influences the normal metabolism (protein,
carbohydrate , lipid and mineral) in the body.
• Effects on growth hormone : As obvious from
the name, GH is essential for is the growth.
The growth-related effects of GH are mediated
through insulin like growth factor I (IFG-I)
which is also known as somatomedin C
produced by liver.

19. Effects on protein metabolism :
• Growth hormone has an anabolic effect on protein
metabolism. It promote the uptake of amino acids into
the tissues ad increases the protein synthesis. The
overall effect of GH is a positive nitrogen balance that
leads to increase in body weight.
• Effects on carbohydrate metabolism :
• Growth hormones is antagonistic to insulin and causes
hyperglycemia. GH increases gluconeogenesis,
decreases glucose utilization , impairs glycolysis and
reduces the tissue uptake of glucose.

20. Effects on lipid metabolism :
• Growth hormone promotes lipolysis in the
adipose tissue and increases the circulatory
levels of free fatty acids and their oxidation. It
increases ketogenesis, particularly in diabetes.
• Effects on mineral metabolism:
growth hormone promotes bone
mineralization and its growth , as clearly
observed in the growing children.

21. Abnormalities of GH production :
• Deficiency of GH :
• impairment in the secretion of growth
hormone in the growing age causes Dwarfism.
The other deficiency metabolic effects are not
that serious in nature.
• Overproduction of GH :
• excessive production of GH causes gigantism
in children and acromegaly in adults.

22. B)Prolactin (PRL) :
• Prolactin (PRL) is also called lactogenic hormone ,
luteotropic hormone , mammotropin or luteotropin.
• Structure of prolactin : PRL hormone with a
molecular mass of about is a protein 23 kDa. It is
secreted by lactotropes, which are acidophilic cells in
the anterior pituitary .
• Disulfide bonds between 4-11,58-73,190-198.

23. Biochemistry functions of prolactin:
• Prolactin is primarily concerned with the
initiation and maintenance of lactation in
mammals. Prolactin increases the levels of
several enzymes involved in carbohydrate and
lipid metabolism. Prolactin promotes HMP shunt ,
increase lipid biosynthesis and stimulates lactose
production in mammary growth of glands.
• Prolactin promotes the growth of corpus luteum
hence also known as luteotropic hormone) and
stimulates the production of progesteone.

24. The glycoprotein hormone :
• The following three hormones are
glycoprotein in nature and posses certain
structural similarities, despite their functional
diversity.
1. Thyroid stimulating hormone (TSH)
2. Follicle stimulating hormone (FSH)
3. Luteinizing hormone (LH)

25. 1)Thyroid stimulating hormone
(TSH):
• The release of TSH from anterior pituitary is
controlled by a feedback mechanism. This
involves the hormones of thyroid gland (T3 and
T4 ) and thyrotropin releasing hormone (TRH) of
hypothalamus.
• Structure of TSH :
• TRS is a of glycoprotein of two subunits , α
subunits 89 amino acids , and β subunits 112
amino acids, molecular weight of about 30,000
kDa.

26. Biochemical function of TSH:
• TSH binds with plasma membrane receptor and
stimulate adenylate cyclase with a consequent
increase in cAMP, exerts the following effects.
• Promotes the uptake of iodide ( iodide pump)
from the circulation by thyroid gland.
• Enhances the conversion of iodine (I-) to active
iodide (I+) , a process known as organification .
• Increases the proteolysis of thyroglobulin to
release T3 and T4 into the circulation .
• TSH increases the synthesis of proteins, nucleic
acids and phospholipids in thyroid gland.

27. TSH

28. Gonadotropic hormones:
• The follicle stimulating hormone (FSH)
luteinizing hormone (LH) and human chorionic
gonadotropin ( hCG) are commonly known as
gonadotropins. All three are glycoproteins.
• The release of FSH and LH from the anterior
pituitary is controlled by gonadotropin
releasing hormone (GnRH) of hypothalamus.

29. Follicle stimulating hormone (FSH):
• Biochemical function of FSH:
• In females, FSH stimulates follicular growth ,
increase the weight of the ovaries and
enhances the production.
• In males, FSH stimulates testosterone
production, required for spermatogenesis. FSH
also promotes growth of seminiferous tubules.

30. Luteinizing hormone (LH):
• Biochemical function of LH:
• Luteinizing hormone stimulate the production
of progesterone from corpus luteum cells in
females and testosterone from leydig cells in
males.
• LH and FSH are collectively responsible for
the development and maintenance of
secondary sexual characters in males.

31. The pro-opimelanocortin (POMC)
peptide family :
• This family consists of the hormonne
adrenocorticotropic hormone (ACTH), melanocyte
stimulating hormone (MSH),and lipotropin (LPH) and
several neuromodulators such as endorphins and
enkephalins.
• The synthesis of POMC family is very interesting. All
the members of POMC are produced from a single
gene of the anterior and intermediate lobes of
pituitary.
• The name pro-opiomelano-cortin is derived since it is a
prohormone to opioids, melanocyte-stimulating
hormone and corticotropin.

32. Adrenocorticotropic hormone (ACTH):
• ACTH is a polypeptide with 39 amino acids
and a molecular weight of 4,500. this
hormone is primarily concerned with the
growth and functions of adrenal cortex.
• The release of ACTH from the anterior
pituitary is under the regulation of
hypothalamic hormone, namely corticotropin
releasing hormone .

33. Structure of ACTH:

34. Biochemical functions of ACTH :
• Stimulate synthesis and secretion of
adrenocortical hormones (glucocorticoids,
androgens and aldosterone).
• ACTH promotes the conversion of cholesterol
to pregenolone in the adrenal cortex.
• It enhances RNA and protein synthesis and
thus promotes adrenocortical growth.
• ACTH increases lipolysis by activating lipase of
adipose tissue.

35. Posterior pituitary :
• Two hormones namely oxytocin and antidiuretic
hormone (ADH, Vasopressin) are produced by the
posterior pituitary gland (neurohypophysis).
• Oxytocin :
• Oxytocin is made up 9 amino acids , it is a non-a
peptides
• Disulfide bond between first amino acids residue
of cysteine –six amino acids residue of cysteine.

36. Structure of oxytocin :

37. Biochemical functions of oxytocin :
• The release of oxytocin from posterior
pituitary gland is caused by the neural
impulses of nipple stimulation . The other
stimuli responsible for oxytocin release
include vaginal and uterine distention.
• Effect on uterus : oxytocin causes the
contraction of pregnant uterus (smooth
muscles) and induces labor.

38. Effect on milk ejection :
• In mammals, oxytocin causes contraction of
myoepithelial cells ( look like smooth muscle
cells ) of breast. This stimulates the squeezing
effect, causing milk ejection from the breast.
• Oxytocin synthesized in the ovary appears to
inhibit the synthesis of steroids.

39. Antidiuretic hormone (ADH):
• The ADH is also known as vasopressin,
• Oxytocin is made up 9 amino acids , it is a
non-a peptides .
• Disulfide bond between first amino acids
residue of cysteine –six amino acids residue of
cysteine.

40. Biochemical functions of ADH :
• ADH is primarily concerned with the regulation of
water balance I the body . It stimulates kidneys to
retain water balance I the body . It stimulates
kidneys to retain water and, thus, increases the
blood pressure.
• In the absence of ADH , the urine output would
be around 20 L/day. ADH acts on the distal
convoluted tubules of kidneys and causes water
reabsorption with a result that the urine output is
around 0.5 -1.5 L/day.

41. Mechanism of action :
• ADH stimulates adenylate cyclase causing
production of Camp .
• Water reabsorption is promoted by Camp .
• Inhibitors of adenylate cyclase (e.g: calcium)
inhibit the activity of ADH. This supports the
view that ADH action is mostly mediated
through Camp.

42. Diabetes insipidus:
• This disorder is characterized by the excretion
of large volumes of dilute urine (polyuria).
• It may be due insufficient levels of ADH or a
defect in the receptors of target cells.