The parathyroid glands produce parathyroid hormone (PTH) which regulates calcium and phosphorus levels in the blood by increasing their absorption in the intestines, resorption in the kidneys, and mobilization from bones. PTH increases calcium levels while decreasing phosphorus. The thyroid gland produces calcitonin which decreases calcium levels. Vitamin D facilitates intestinal calcium absorption. Hyperparathyroidism is excessive PTH production and can be primary from adenomas or hyperplasia, or secondary from low calcium levels due to kidney disease or vitamin D deficiency. Complications include osteoporosis, kidney stones, and heart disease.

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Parathyroid gland
• Parathyroid glands are small endocrine glands in the neck of humans that
produce parathyroid hormone.
• Humans usually have four parathyroid glands, variably located on the back of
the thyroid gland.
• The parathyroid glands maintain proper levels of both calcium and phosphorus in
your body by turning the secretion of parathyroid hormone (PTH) off or on.
• Parathyroid hormone (also known as parathormone) is a small protein that takes
part in the control of calcium and phosphate homeostasis, as well as bone
physiology.
• Parathyroid hormone has effects antagonistic to those of calcitonin.
- Calcitonin (a hormone produced by the thyroid gland) acts to decrease calcium
concentration.

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♦ Calcium:
• PTH increases blood calcium levels by:-
- directly stimulating osteoblasts and thereby indirectly stimulating osteoclasts (to break down
bone and release calcium. (Efflux of calcium from bone)
- PTH increases gastrointestinal calcium absorption by activating vitamin D, and promotes
calcium conservation (reabsorption) by the kidneys (Decrease loss of calcium in urine).
PTH action in Calcium regulation

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♦ Vitamin D and Calcium : (‫المحاضرة‬ ‫في‬ ‫منو‬ ‫كبير‬ ‫جسء‬ ‫شرحت‬ ‫الدكتوره‬ ‫ولكن‬ ‫االنترنت‬ ‫من‬ ‫زياده‬)
• The body needs vitamin D to absorb calcium.
• Without enough vitamin D, one can’t form enough of the hormone calcitriol (known as the
“active vitamin D”).
• This in turn leads to insufficient calcium absorption from the diet.
• In this situation, the body must take calcium from its stores in the skeleton, which weakens
existing bone and prevents the formation of strong, new bone.
• You can get vitamin D in three ways: through the skin, from the diet, and from supplements.
• Vitamin D-rich foods such as egg yolks, saltwater fish, liver, and fortified milk, Mushroom,
Orange juice.
♦ Vitamin D Deficiency:
• Vitamin D deficiency has been associated with rickets, a disease in which the bone tissue doesn't
properly mineralize, leading to soft bones and skeletal deformities.
• These are common risk factors for vitamin D deficiency:
 Having dark skin.
 Being elderly.
 Being overweight or obese.
 Not eating much fish or milk.
 Living far from the equator where there is little sun year-round.
 Always using sunscreen when going out.
 Staying indoors.

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Phosphate:
- PTH is the major regulator of serum phosphate concentrations via actions on the kidney.
- It is an inhibitor of proximal tubular reabsorption of phosphorus (Increase excretion of
phosphate on renal tubules).
- Through activation of vitamin D the absorption (intestinal) of Phosphate is increased.
Watch on YouTube: https://www.youtube.com/watch?v=EEM0iRJNhU8
Hyperparathyroidism
• Hyperparathyroidism is an excess of parathyroid hormone in the bloodstream due to
overactivity of one or more of the body's four parathyroid glands.
• These glands are about the size of a grain of rice and are located in your neck.
• The parathyroid glands produce parathyroid hormone, which helps maintain an appropriate
balance of calcium in the bloodstream and in tissues that depend on calcium for proper
functioning.
• Two types of hyperparathyroidism exist:
- In primary hyperparathyroidism, an enlargement of one or more of the parathyroid
glands causes overproduction of the hormone, resulting in high levels of calcium in the
blood (hypercalcemia), which can cause a variety of health problems.
- Secondary hyperparathyroidism occurs as a result of another disease that initially
causes low levels of calcium in the body and over time, increased parathyroid hormone
levels occur.

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♦ Symptoms may be so mild and nonspecific that they don't seem at all related to
parathyroid function, or they may be severe.
The range of signs and symptoms include:
 Fragile bones that easily fracture (osteoporosis)
 Kidney stones
 Excessive urination
 Abdominal pain
 Tiring easily or weakness
 Depression or forgetfulness
 Bone and joint pain
 Frequent complaints of illness with no apparent cause
 Nausea, vomiting or loss of appetite
• The parathyroid glands maintain proper levels of both calcium and phosphorus in
your body by turning the secretion of parathyroid hormone (PTH) off or on
• Vitamin D also is involved in regulating the amount of calcium in your blood.
• Normally, this balancing act works well.
• When calcium levels in your blood fall too low, your parathyroid glands secrete
enough PTH to restore the balance.
- PTH raises calcium levels by releasing calcium from your bones and
increasing the amount of calcium absorbed from your small intestine.
• When blood-calcium levels are too high, the parathyroid glands produce less
PTH.
- But sometimes one or more of these glands produce too much hormone,
leading to abnormally high levels of calcium (hypercalcemia) and low levels
of phosphorus in your blood.

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Primary hyperparathyroidism
• Primary hyperparathyroidism occurs because of some problem with one or
more of the four parathyroid glands:
• A noncancerous growth (adenoma) on a gland is the most common cause.
• Enlargement (hyperplasia) of two or more parathyroid glands accounts for
most other cases.
• A cancerous (malignant) tumor is a rare cause of primary
hyperparathyroidism.
• Primary hyperparathyroidism usually occurs randomly, but some people
inherit a gene that causes the disorder.
Secondary hyperparathyroidism
• Secondary hyperparathyroidism is the result of another condition that lowers
calcium levels.
• Therefore, your parathyroid glands overwork to compensate for the loss of
calcium.
♦ Factors that may contribute to secondary hyperparathyroidism include:
• Severe calcium deficiency: Your body may not get enough calcium from
your diet, often because your digestive system doesn't absorb the calcium
from it.
• Severe vitamin D deficiency: Vitamin D helps maintain appropriate levels of
calcium in the blood, and it helps your digestive system absorb calcium from
your food.
• Your body produces vitamin D when your skin is exposed to sunlight, and
you consume some vitamin D in food
- If you don't get enough vitamin D, then calcium levels may drop.
• Chronic kidney failure: Your kidneys convert vitamin D into a form that
your body can use.
- If your kidneys function poorly, usable vitamin D may decline and calcium
levels drop.
- Chronic kidney failure is the most common cause of secondary
hyperparathyroidism.

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Complications
• Complications of hyperparathyroidism are primarily related to the long-term effect of too little
calcium in your bones and too much calcium circulating in your bloodstream.
• Common complications include:
• Osteoporosis.
- The loss of calcium often results in weak, brittle bones that fracture easily (osteoporosis).
• Kidney stones.
- The excess of calcium in your blood may lead to excess calcium in your urine, which can
cause small, hard deposits of calcium and other substances to form in your kidneys.
- A kidney stone usually causes significant pain as it passes through the urinary tract.
• Cardiovascular disease.
- Although the exact cause-and-effect link is unclear, high calcium levels are associated
with cardiovascular conditions, such as high blood pressure (hypertension) and certain
types of heart disease.
• Neonatal hypoparathyroidism.
- Severe, untreated hyperparathyroidism in pregnant women may cause dangerously low
levels of calcium in newborns.
Degradation of parathormone (Parathyroid hormone)
• Half-life of PTH is approximately 10 minutes.
• Most of the newly synthesized PTH is degraded immediately after its synthesis and only a
minority enters the bloodstream.
• Peripheral degradation of PTH takes place mainly in liver and kidneys.
• Inside the liver Kupffer cells, PTH undergoes proteolysis to carboxy- and amino-fragments.
• Amino-fragments are quickly degraded, but carboxy-fragments remain in the circulation and
leave the body through kidneys.

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Calcitonin
• Calcitonin is a hormone that the C-cells in the thyroid gland produce and release.
• It opposes the action of the parathyroid hormone, helping to regulate the blood’s calcium
and phosphate levels.
• Calcitonin works to control calcium and potassium levels.
• It does this by inhibiting the activity of the osteoclasts, the cells that break down bone.
- Osteoclast: a type of bone cell that breaks down bone tissue.
- Osteoblast: are the cells that form new bone.
♦ Calcitonin:
- Decreases blood calcium levels by causing its deposition on bone.
- Antagonistic to parathyroid hormone.
- Produced by C (parafollicular) cells.
• Sometimes high calcitonin levels can point to a rare type of medullary thyroid cancer.
• This cancer, which starts in the C-cells, can be connected to multiple endocrine neoplasia type
2b and multiple endocrine neoplasia type 2a.
• However, the calcitonin levels do not cause the cancer.

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The pituitary and Hypothalamus
• The pituitary gland is often called the master gland because it controls several other hormone
glands in your body.
♦ Hormones produced by the pituitary gland:
• The two sections of the pituitary gland produce a number of different hormones which act on
different target glands or cells.
♣ Anterior pituitary
• Adrenocorticotrophic hormone (ACTH)
• Thyroid-stimulating hormone (TSH)
• Luteinising hormone (LH)
• Follicle-stimulating hormone (FSH)
• Prolactin (PRL)
• Growth hormone (GH)
• Melanocyte-stimulating hormone (MSH)
♣ Posterior pituitary
• Anti-diuretic hormone (ADH)
• Oxytocin

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• The secretion of hormones from the anterior pituitary is controlled by the production of
hormones by the hypothalamus.
• Although there are a number of different hormones they can be split into two main types:
• hormones that tell the pituitary to switch on production of a hormone (a releasing
hormone)
• hormones that tell the pituitary to switch off production of a hormone (an inhibiting
hormone).
• The hormones secreted by the posterior pituitary
are produced in the hypothalamus and then passed
down a tube between the hypothalamus and the
pituitary (the pituitary stalk) when they are then
secreted into the blood.

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Diseases and Disorders of the Pituitary Gland
• Pituitary tumors are the most common pituitary disorder, and many adults have them.
• There are two types of pituitary tumors—secretory and non-secretory.
- Secretory tumors secrete too much of a hormone.
- Non-secretory tumors don’t secrete excess hormone.
Symptoms related to specific conditions
♣ Diabetes Insipidus (DI)
• Due to a lack of the hormone vasopressin (antidiuretic hormone),this can be due to damage to
the hypothalamus or pituitary gland or genetics.
• Passing excessive urine much more than usual during the day and frequently through the
night
• Urine is very pale, possibly clear and doesn’t concentrate
• Extreme thirst, which cannot be quenched
• Preference of icy cold drinks
• Headaches (which may be due to dehydration)
• Exhaustion
• Shivering
• Nausea
• Dehydration symptoms: parched mouth, cracked lips,
coated tongue, dry eyes and dry skin
• Most foods intolerable with a preference to drink
fluids
• Weight loss

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♣ Cushing's disease
• Cushing's disease is a cause of Cushing's syndrome characterised by increased secretion
of adrenocorticotropic hormone (ACTH) from the anterior pituitary
• Weight gain to trunk of body, plus rounding of face
• Fatty hump at top of spine/back
• Flushed appearance and roundness of face
• Low mood, can feel depressed
• Loss of bone density (if left untreated over time) due to
excess cortisol
• Extreme mood swings
• Weakness, possible muscle wasting
• Darkening of skin pigmentation
• Dark purple striae (similar to stretch marks on abdomen
and tops of thighs)
• Hirsutism (extreme hairiness)
♣ Prolactinoma
• A prolactinoma is a benign tumor (adenoma) of the pituitary gland that produces a hormone called prolactin.
• Loss of periods (female)
• Infertility
• Low or lack of libido
• Weight gain bloated stomach
• Lethargy/exhaustion, falling asleep during day
• Headaches
• Milk/fluid excreting from nipples when not pregnant (males can have this too)
♣ Hypopituitarism
• Hypopituitarism is the decreased secretion of one or more of the eight hormones normally produced by
the pituitary gland at the base of the brain
• (can include cortisol, growth hormone and thyroid deficiencies)
• Flu type feelings low or no cortisol in body, regular colds and/or infections 'hung over’
type feeling without having drunk alcohol
• No body temperature control either feeling too hot, or too cold
• Nausea
• Mood swings feelings of depression, apathy or low mood
• Joint aches and pains, and/or poor muscle tone
• Exhaustion
• Constipation
• Difficulty finding words
• Poor sleep patterns
• Low blood pressure feeling light-headed • Pale pallor