Parathyroid Hormone- PTH

Parathyroid Hormone- PTH
By:
Dr. Inayat ur Rahman Abbasi
MBBS, M.Phil, CHPE & MHPE
Professor of Biochemistry
Northwest School of Medicine
Peshawar- Pakistan

Hormone
• Hormone: A chemical substance produced in
the body that controls and regulates the
activity of certain cells or organs.
• Many Hormones are secreted by special
glands. Hormones are the body's chemical
messengers and are part of the Endocrine
system.
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Parathyroid Hormone- LCF- Dr. Inayat
Abbasi

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Types of Hormones
Hormone class Components Examples
Amine Hormone Amino acids with modified
Groups.
Adrenaline, Thyroxin
Protein Hormone Long chain of linked
Amino acids.
ADH , Insulin
Steroid Hormone Derived from the lipid
Cholesterol.
Cortisol, Aldosterone,
Estrogen
Peptide Hormone Short chain of linked
Amino acids.
Glucagon, Prolactin, ACTH
Parathyroid Hormone
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Parathyroid Hormone
• Parathyroid hormone is secreted from four
parathyroid glands, which are small glands in
the neck, located behind the thyroid gland.
• Parathyroid Hormones is secreted by the chief
cells of the parathyroid glands as polypeptide
containing 84 amino acids.
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Parathyroid Hormone
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Main Function
• It causes to increase the concentration of
calcium (Ca+2) in the blood, by acting on three
important systems; bones, gut & kidneys.
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Regulation
• How is parathyroid hormone controlled?
• Parathyroid hormone is mainly controlled by
the negative feedback of calcium levels in the
blood to the parathyroid glands.
• Low calcium levels in the blood stimulate
parathyroid hormone secretion, whereas high
calcium levels in the blood prevent its release.
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• Parathyroid hormone regulates calcium levels
in the blood, largely by increasing the levels
when they are too low. It does this through its
actions on the kidneys, bones and intestine:
• Mobilization of calcium from bone:
• Bones – parathyroid hormone stimulates the
release of calcium from large calcium stores in
the bones into the blood stream. This
increases bone destruction and decreases the
formation of new bone.
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• Suppression of calcium loss in urine:
• Kidneys –parathyroid hormone reduces loss of
calcium in urine. Parathyroid hormone also
stimulates the production of active vitamin D
in the kidneys.
• Enhancing absorption of calcium from the
small intestine:
• Intestine –parathyroid hormone indirectly
increases calcium absorption from food in the
intestine, via its effects on vitamin-D
metabolism.
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Main Actions
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Synthesis
• Serum PTH concentrations are dependent
upon the release of PTH stored in secretary
granules within the parathyroid gland and by
the synthesis of new PTH.
• Ca2+, phosphorus, and vitamin D metabolites
play a role in regulating PTH release and
synthesis.
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Synthesis Flow-chart
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• Parathyroid hormone (PTH) is a polypeptide of
84 AA that is synthesized and secreted by the
parathyroid glands. It acts on the target
organs; bone, intestine and kidney, to
promote the flow of calcium into the
extracellular fluid.
• The secretion of PTH, in turn is regulated by
negative feedback with calcium conc in blood
and extracellular fluid, thus maintaining
calcium homeostasis.
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Difference b/w High & Low Ca level
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• The two most important hormones for
maintaining calcium levels in the body are
parathyroid hormone (PTH) and 1,25(OH)2D
(the active form of vitamin D).
• The major regulator is PTH, its secretion is
stimulated by hypocalcemia, and it works
through three mechanisms to increase Ca++
levels:
• 1. PTH stimulates the release of Ca++ from
bone, in part by stimulating bone resorption.
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• 2. PTH decreases urinary loss of Ca++ by stimulating Ca++
reabsorption.
• 3. PTH indirectly stimulates Ca++ absorption in the small
intestine by stimulating synthesis of 1,25(OH)2D in the kidney.
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Ca+2 Homeostasis & PTH
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Summary
• PTH increases blood calcium concentrations
when calcium ion levels fall below normal.
• First, PTH enhances reabsorption of calcium
by the kidneys; it then stimulates osteoclast
activity and inhibits osteoblast activity.
• Finally, PTH stimulates synthesis and secretion
of calcitriol by the kidneys, which enhances
Ca+2 absorption by the digestive system.
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Hyperparathyroidism:
• CAUSES: The most common disease of parathyroid
glands is hyperparathyroidism, which is characterized
by excess PTH hormone, regardless of calcium levels.
In other words, the parathyroid glands continue to
make large amounts of PTH .
• SYMPTOMS: Bone pain, Muscle weakness, Long
• bone fractures, kidney stones.
• Treatment : Optimize the levels of serum calcium
and phosphate ions.
• Control of PTH and vitamin D.
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Hyperparathyroidism:
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Excessive secretion of parathyroid
hormone is seen in two forms:
• Primary hyperparathyroidism is the result of
parathyroid gland disease, most commonly
due to a parathyroid tumor (adenoma) which
secretes the PTH-hormone without proper
regulation.
• Common manifestations of this disorder are
chronic elevations of blood calcium
concentration (hypercalcemia), kidney stones
and decalcification of bone.
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• Secondary hyperparathyroidism is the situation where
disease outside of the parathyroid gland leads to
excessive secretion of parathyroid hormone. A
common cause of this disorder is kidney disease - if the
kidneys are unable to reabsorb calcium, blood calcium
levels will fall, stimulating continual secretion of
parathyroid hormone to maintain normal calcium
levels in blood.
• It can also result from inadequate nutrition- example,
diets that are deficient in calcium or vitamin D.
• A prominent effect of secondary hyperparathyroidism
is decalcification of bone, leading to pathologic
fractures or "rubber bones".
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Hypoparathyroidism
• CAUSES: Hypoparathyroidism is the combination
of symptoms due to inadequate parathyroid
hormone production. This leads to decreased
blood levels of calcium (hypocalcemia) and
increased levels of blood phosphorus
(hyperphosphatemia).
• SYMPTOMS: Decreased ca ions levels in blood,
sensitive nerves, uncontrollable spasms of the
limbs.
• Treatment :
• Daily calcium and vitamin D supplements
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Hypoparathyroidism
• Inadequate production of parathyroid hormone -
hypoparathyroidism - typically results in
decreased concentrations of calcium and
increased phosphorus levels in blood.
• Common causes are surgical removal of the
parathyroid glands and disease processes that
lead to destruction of parathyroid glands.
• The resulting hypocalcemia often leads to tetany
& convulsions and can be life-threatening.
• Treatment focuses on restoring normal blood
calcium concentrations by calcium infusions, oral
calcium supplements and vitamin D therapy.
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Osteoporosis
• CAUSES: Osteoporosis: When one of the
parathyroid glands is overactive, it releases too much
PTH hormone. This causes your bones to release
calcium constantly into the blood stream. Without
enough calcium in your bones, they lose their density
and hardness.
• SYMPTOMS: Bone pain or tenderness
• Neck or lower back pain due to fractures, stoped
posture
• Treatment: Biphosphonates, vitamin D.
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Osteoporosis
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References
• Books: Harpers lllustrated Biochemistry-Robert .k.Murry , Daryl.k.Granner
• JOURNALS : The mechanism of parathyroid hormone action on calcium reabsorption by the distal
tubule. Bouhtilauy ,lajeunesse.- Endocrine society ( PUBMED) NCBI
• The Regulation of Parathyroid Hormone Secretion and Synthesis :Published in final edited form as: J Am
Soc Nephrol. 2011 February ; 22(2): 216–224. doi:10.1681/ASN.2010020186.
• Parathyroid interaction: implications in chronic kidney disease-kidney international journal Volume77,
issue 4, febuary 2010 , pages 292-298
• Biosynthesis of Parathyroid Hormone: The New England journal of Medicine journal September 14, 1978
,DOI : 1110.1056 /NEJM 19780914299110
• The Regulation of Parathyroid Hormone Secretion and Synthesis: Journal of the American Society of
nephrology Published online before printDecember 16, 2010, doi:10.1681/ASN.2010020186
• Stimulation of ovine placental transport of calcium and magnesium by mid‐molecule fragments of
human parathyroid hormone‐related protein
• INTERNET: https://en.wikipedia.org/wiki/Parathyroid_hormone
• http://emedicine.medscape.com/article/2089334-overview
• http://www.parathyroid.com/hypoparathyroidism.htm
• http://www.parathyroid.com/parathyroid-function.htm
• https://www.endocrineweb.com/conditions/parathyroid/parathyroid-function
• https://www.hormone.org/hormones-and-health/hormones/parathyroid-hormone
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• THANK YOU VERY MUCH..
• ANY QUESTION?
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Parathyroid Hormone- PTH

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