Osteoporosis - causes, symptoms, diagnosis, treatment, pathology
Summary
TLDRيشير مصطلح هشاشة العظام إلى انخفاض كثافة العظام بسبب زيادة تكسير العظام مقارنة بتكوينها. تتأثر العظام الإسفنجية والعظام القشرية بشكل خاص، مما يزيد من خطر الكسور. يتم تشخيص هشاشة العظام باستخدام مسح DEXA لقياس كثافة العظام. الأسباب تشمل انخفاض مستويات الاستروجين والكالسيوم، والعوامل الوراثية، وسوء التغذية، وقلة النشاط البدني، وبعض الأدوية والأمراض. العلاج يشمل أدوية البايفوسفونات، وتيريباراتايد، ومدرات الثيازايد، والأدوية الأخرى مثل دينوسوماب ورالوكسيفين. الأنواع الشائعة هي هشاشة العظام بعد سن اليأس والشيخوخة، حيث تكون الكسور الفقرية الأكثر شيوعًا.
Takeaways
- 🦴 'Osteoporosis' is a condition characterized by increased bone breakdown compared to new bone formation, leading to porous and fragile bones.
- 🏗️ Bones have an external 'cortical' layer and an internal 'trabecular' or 'spongy' layer, which includes the trabeculae that provide structural support.
- 🌀 Cortical bone is composed of 'osteons' which contain 'Haversian canals' for blood supply and innervation, surrounded by concentric 'lamellae'.
- 🧬 The organic part of lamellae is made mostly of collagen, while the inorganic part, 'hydroxyapatite', is primarily calcium phosphate.
- 🔄 Bone is dynamic tissue undergoing 'remodeling' every few years, involving 'resorption' by osteoclasts and 'formation' by osteoblasts.
- 📈 Bone remodeling is regulated by serum calcium levels, influenced by parathyroid hormone (PTH), calcitonin, and vitamin D.
- 🚀 PTH increases bone resorption to raise serum calcium levels, while calcitonin promotes bone formation and decreases resorption.
- 💊 Vitamin D aids in calcium absorption, thus promoting bone formation and decreasing resorption.
- 📊 Peak bone mass, influenced by genetics and nutrition, is usually reached by age twenty to twenty-nine, earlier in females.
- 🚶♀️ Factors accelerating bone mass loss include low estrogen levels, alcohol, smoking, certain drugs, and physical inactivity.
- 👵 The two common types of osteoporosis are 'postmenopausal' and 'senile', with the former linked to decreased estrogen levels and the latter to osteoblasts' reduced bone formation ability.
- 🩺 Osteoporosis is often asymptomatic until a fracture occurs, with vertebral compression fractures being the most common.
- 🛑 Diagnosis is made using a DEXA scan, with a T score of -2.5 or less indicating osteoporosis.
- 💊 Treatment options include bisphosphonate drugs, teriparatide, hydrochlorothiazide, denosumab, and raloxifene.
Q & A
ما هو العظم الناجم (Osteoporosis)؟
-العظم الناجم هو حالة تسبب انخفاض كثافة العظم بسبب زيادة تدمير العظم مقارنة بتكوين العظم الجديد، مما يؤدي إلى ت疏松 في العظم وت減少し كثافة العظم حتى وقوف الكسر.
ما هي الهيكلة الداخلية للعظم؟
-تتكون العظم من طبقة خارجية صلبة تسمى العظم القرشي وطبقة داخلية من العظم الناعمة أو العظم الشبكي، يتكون من trabeculae توفر الدعم الهيكلي للعظم الشبكي.
ما هي الوظيفة الرئيسية لـ osteocytes في العظم؟
-تتواجد الخلايا العظمية (osteocytes) في الفراغات التي تسمى lacunae، وتلعب دورًا في تفاعل العظم وصيانةه.
كيف تحدث عملية إعادة صيانة العظم؟
-تتضمن إعادة صيانة العظم خطوتين: تدمير العظم من قبل الخلايا الخاصة المسماة osteoclasts، وتكوين العظم من قبل الخلايا الأخرى المسماة osteoblasts.
ما هي العوامل الحيوية التي تتحكم في إعادة صيانة العظم؟
-تعتمد إعادة صيانة العظم على مستويات الكالسيوم في الدم، التي تحافظ عليها من خلال توازن بين هرمون العظم (PTH)، وهرمون الكالسيتونين، وفيتامينات D.
كيف يؤثر هرمون العظم (PTH) على مستويات الكالسيوم في الدم؟
-يُنتج هرمون العظم من أطراف العظم في استجابة لانخفاض مستويات الكالسيوم في الدم، ويزيد تدمير العظم لإطلاق الكالسيوم في الدم.
ما هي العوامل التي تعزز خطر الإصابة بالعظم الناجم؟
-تعزز عوامل مثل انخفاض مستويات الإسترين بعد ال menoopause، وانخفاض مستويات الكالسيوم في الدم، واستهلاك الكحول، وتدخين، وبعض الأدوية مثل glucocorticoids، وheparin، وL thyroxine، وعدم النشاط الجسدي، خوفًا من بعض الأمراض مثل Turner syndrome و hyperprolactinemia و Klinefelter syndrome و Cushing syndrome و diabetes mellitus.
ما هي الأنواع المشتركة للعظم الناجم؟
-تتضمن العظم الناجم النوعين الأكثر شيوعًا: العظم الناجم بعد ال menoopause والعظم الناجم الشيعي.
ماذا يشير إلى التشخيص المبكر للعظم الناجم؟
-يُستخدم التشخيص المبكر للعظم الناجم جهاز DEXA لفحص كثافة العظم، ويقارن النتيجة مع كثافة العظم الطبيعية للبالغ الصحیح.
ما هي الأدوية التي تستخدم في علاج العظم الناجم؟
-تعتمد الأدوية التي تستخدم في علاج العظم الناجم مثل bisphosphonate مثل alendronate و rizendronate، و في الحالات المتقدمة، يُستخدم teriparatide، وهو هرمون تشريعي لهرمون العظم.
ما هي العوامل التي تحدد كثافة العظم الذرية؟
-تحدد العوامل التي تحدد كثافة العظم الذرية الجينات والغذاء، مما يعني أن استهلاك كافي من وتامين D يزيد كثافة العظم الذرية.
كيف يمكن تحليل كثافة العظم؟
-يمكن تحليل كثافة العظم من خلال استعمال جهاز DEXA، ويتم إعطاء نتيجة T، ويعد النتيجة السلبية 2.5 أو أقل كتشخيص للعظم الناجم.
Outlines
🦴 Understanding Osteoporosis and Bone Structure
The first paragraph introduces osteoporosis as a condition where bone breakdown exceeds new bone formation, leading to porous and fragile bones. It explains the structure of bones, including the cortical and trabecular layers, osteons, Haversian canals, lamellae, and the role of osteocytes. The dynamic nature of bone tissue and the process of bone remodeling, involving osteoclasts and osteoblasts, are detailed. The importance of serum calcium levels and the influence of parathyroid hormone, calcitonin, and vitamin D on bone health are discussed. Factors affecting peak bone mass, such as genetics, nutrition, strength training, and hormones, are also highlighted. The paragraph concludes with information on how an imbalance between osteoclast and osteoblast activity can lead to osteoporosis and its distinguishing features compared to osteomalacia.
🚺 Types and Treatment of Osteoporosis
The second paragraph delves into the two most common types of osteoporosis: postmenopausal and senile. It describes how decreased estrogen levels in postmenopausal women increase bone resorption, while in senile osteoporosis, osteoblasts' bone formation capacity declines with age. The paragraph outlines the typical symptoms of osteoporosis, which often manifest as fractures, particularly vertebral compression fractures leading to back pain, height loss, and a hunched posture. Other types of fractures associated with osteoporosis are also mentioned. The diagnosis of osteoporosis using DEXA scans and the T score criteria are explained. Treatment options include bisphosphonate drugs, teriparatide, hydrochlorothiazide, denosumab, and raloxifene, each targeting different aspects of bone resorption and formation. The paragraph concludes with a recap of the key points about osteoporosis, its diagnosis, and treatment.
Mindmap
Keywords
💡استيئوس
💡عظم العظم
💡عظم الشبك
💡أوستونات
💡هيدروكسي أباتيت
💡كلاغونيس
💡تجديد العظم
💡هورمون العظم
💡كالسيوم الدمي
💡استيئوس ال绝经後
💡تشخيص استيئوس
Highlights
Osteoporosis is characterized by increased bone breakdown compared to new bone formation, leading to porous and potentially fragile bones.
Bones consist of a hard external layer, cortical bone, and an internal spongy bone made of trabeculae for structural support.
Cortical bone is composed of osteons with Haversian canals for blood supply and innervation, surrounded by concentric lamellae.
Lamellae contain collagen and hydroxyapatite, providing organic and inorganic components for bone strength.
Bone is dynamic, with spongy bone replaced every 3-4 years and compact bone every 10 years through bone remodeling.
Bone remodeling involves bone resorption by osteoclasts and bone formation by osteoblasts.
Serum calcium levels regulate bone remodeling, balanced by PTH, calcitonin, and vitamin D.
PTH increases bone resorption to raise serum calcium levels in response to low calcium.
Calcitonin opposes PTH, promoting bone formation and decreasing bone resorption in response to high serum calcium.
Vitamin D enhances calcium absorption in the gut, promoting bone formation and decreasing bone resorption.
Peak bone mass is influenced by genetics, nutrition, and factors like strength training and certain hormones.
Osteoporosis occurs when osteoclasts break down bone faster than osteoblasts can rebuild it, reducing bone mass.
Osteoporotic bones have fewer trabeculae, thinning cortical bone, and widened Haversian canals, increasing fracture risk.
Vertebrae, shoulder blades, and ribs are at high risk for fragility fractures due to their spongy bone composition.
Factors accelerating bone mass loss include low estrogen levels, low serum calcium, alcohol, smoking, certain drugs, and physical inactivity.
Diseases like Turner syndrome, hyperprolactinemia, Klinefelter syndrome, Cushing syndrome, and diabetes can cause osteoporosis.
Postmenopausal and senile osteoporosis are the two most common types, with different causes for bone resorption.
Osteoporosis is often asymptomatic until a fracture occurs, with vertebral fractures being the most common.
DEXA scan is used for diagnosing osteoporosis by comparing bone density to that of a normal adult, with a T score of -2.5 or less indicating the condition.
Treatment for osteoporosis includes bisphosphonate drugs, teriparatide, hydrochlorothiazide, denosumab, and raloxifene.
Teriparatide, despite stimulating bone resorption, can increase bone formation when used in intermittent injections.
Hydrochlorothiazide treats osteoporosis by boosting calcium retention and stimulating osteoblast differentiation.
Denosumab and raloxifene are medications used for postmenopausal osteoporosis, targeting osteoclasts and estrogen receptors respectively.
Transcripts
Osteo refers to bones, and porosis means pores.
So osteoporosis is when there's a higher breakdown of bone in comparison
to the formation of new bone, which results in porous bones,
meaning a decrease in bone density to the point of potential fracture.
Looking at a cross section of a bone, there's a hard external layer
known as the cortical bone,
and a soft internal layer of spongy bone,
or trabecular bone, that is composed of trabeculae.
The trabeculae are like a framework of beams
that give structural support to the spongy bone.
The cortical bone, in turn, is made up
of many functional pipe-like units called osteons,
which run through the length of the bone.
In the center of these osteons, there are hollow spaces
called Haversian canals, which contain the blood supply
and innervation for the bone cells.
Around the Haversian canals, there are concentric lamellae
which look a bit like tree rings.
The lamellae have an organic part, which is mostly collagen,
and an inorganic part called hydroxyapatite,
which is mostly calcium phosphate.
In between neighboring lamellae, there are spaces called lacunae,
which contain bone cells called osteocytes.
At first glance, bone may appear inert and unchanging,
but it's actually a very dynamic tissue.
In fact, spongy bone is replaced every three to four years
and compact bone is replaced every ten years in a process called bone remodeling,
which has two steps: bone resorption,
when specialized cells called osteoclasts break down bone;
and bone formation, which is when another type of cells
called osteoblasts form new bone.
Bone remodeling as a whole is highly dependent on serum calcium levels,
which in turn are kept in the normal range by a balance between
parathyroid hormone or PTH, calcitonin, and vitamin D.
Parathyroid hormone is produced by the parathyroid glands
in response to low serum calcium,
and it increases bone resorption to release calcium into the bloodstream.
On the other hand, calcitonin is produced by the thyroid gland
in response to high serum calcium.
So it opposes the action of PTH,
therefore promoting bone formation and decreasing bone resorption.
Finally, vitamin D promotes calcium absorption in the gut,
so it increases serum calcium,
promoting bone formation and decreasing bone resorption.
The balance between these regulatory factors results in a peak bone mass,
usually by age twenty to twenty nine,
and this usually occurs earlier in females than in males.
Factors that determine the peak bone mass are genetics, and nutrition,
meaning adequate vitamin D intake increases bone peak mass.
Finally, strength training increases peak bone mass,
as well as hormones like estrogens and androgens
that inhibit bone resorption.
Okay, now when osteoclasts break down bone faster than the osteoblasts
can rebuild it, it results in the lowering of the bone mass
and eventually in osteoporosis.
If we zoom into a cross section of an osteoporotic bone,
it will show normal cells with normal mineralization,
which differentiates it from osteomalacia, where there's a lack of mineralization.
So with osteoporosis, abnormal findings include
fewer trabeculae in the spongy bone and thinning of the cortical bone,
as well as the widening of the Haversian canals.
These bone changes increase the risk of fracture,
and they're known as fragility or pathologic fractures.
Some bones, like the vertebrae, shoulder blades, and ribs
consist mainly of spongy bone, so they're in great risk
of fragility fractures.
Factors that accelerate bone mass loss and increase the risk of osteoporosis
are low estrogen levels, like after menopause,
and low serum calcium.
Additional factors include alcohol consumption,
smoking, drugs (like glucocorticoids, which decrease calcium absorption
from the gut through the antagonism of vitamin D,)
and drugs like heparin and l thyroxine.
Another factor is physical inactivity,
as seen in astronauts in a zero gravity environment
where they just don't use their musculoskeletal system
as hard as when they're on Earth.
As a result, bone deposition decreases due to a lack of stress,
while resorption increases.
There are also diseases that can cause osteoporosis like Turner syndrome,
hyperprolactinemia, Klinefelter syndrome, Cushing syndrome, and diabetes mellitus.
Now, the two most common types of osteoporosis are:
postmenopausal osteoporosis and senile osteoporosis.
In postmenopausal osteoporosis,
decreased estrogen levels lead to increased bone resorption.
With senile osteoporosis, on the other hand,
it's believed that osteoblasts just gradually lose the ability
to form bone,
while the osteoclasts keep doing their thing unabated.
So, bone resorption usually overtakes bone formation
around the eighth decade of life.
People with osteoporosis don't usually have symptoms until a fracture occurs.
The most common type of fractures are vertebral fractures,
also known as compression fractures, and that occurs
when one or more bones in the spine weaken and shatter.
Vertebral fractures cause back pain, height loss, and a hunched posture.
Femoral neck fractures and distal radius fractures
can also occur, and they're often associated
with postmenopausal osteoporosis.
Osteoporosis is usually diagnosed with a dual energy X-ray absorptiometry
or DEXA scan, which tests for bone density.
The test compares an individual's bone density to that of a normal adult,
which yields the result or the T score.
A T score of less than or equal to negative two point five (-2.5)
is diagnostic of osteoporosis.
Treatment for osteoporosis usually relies on bisphosphonate drugs
like alendronate and rizendronate.
If osteoporosis is really advanced,
teriparatide, a recombinant parathyroid hormone, can be used.
Now, even though parathyroid hormone stimulates bone resorption,
it's been found that intermittent injections
with teriparatide activates osteoblasts more than osteoclasts,
therefore increasing bone formation.
Interestingly, a thiazide diuretic like hydrochlorothiazide
can be used to treat osteoporosis as well.
Hydrochlorothiazide boosts calcium retention in the kidney
and directly stimulates osteoblast differentiation,
therefore decreasing mineral bone loss.
Finally, medications like denosumab,
which is a monoclonal antibody that inhibits osteoclasts,
and raloxifene, which is a selective estrogen receptor modulator
can be used for postmenopausal osteoporosis.
Alright. As a quick recap,
osteoporosis refers to decreased bone density
on account of increased bone resorption compared to bone formation.
In osteoporosis, there is thinning of the cortical bone,
widening of the Haversian canals,
and a decrease in the number of trabeculae in the spongy bone.
There are two common types of osteoporosis.
These are senile osteoporosis and postmenopausal osteoporosis.
The most common type of fracture
in osteoporosis is a vertebral compression fracture.
Diagnosis is done with the dual energy X-ray absorptiometry, or DEXA scan,
where a T score equal to or less than negative two point five (-2.5)
equals osteoporosis.
First line treatment relies on bisphosphonate drugs
like alendronate and rizendronate.
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