The Intern At Work: Internal Medicine
Jun 28, 2026 · 22 min · 10 segments
Send us Fan Mail In this episode, we discuss a comprehensive approach to osteoporosis. Written by: Dr. Sharon Pritchard. Reviewed by: Dr. Nadine…
[upbeat music] Time for a minute physiology.
To understand the physiology behind osteoporosis, there are two main cell types we will focus on.
Osteoblasts are cells that form bone, while osteoclasts resorb or break down bone.
Important building blocks for bones include calcium and phosphate.
Vitamin D also plays a role in this as it increases calcium absorption in the gut and reabsorption in the kidneys.
In osteoporosis, the breakdown of bone by osteoclasts surpass the formation of bone by osteoblasts.
The activity of osteoclasts and osteoblasts are regulated by several other proteins and pathways.
We won't worry too much about going into specific details of these pathways today, but a useful one to know is the RANK/RANKL/OPG system.
In this pathway, RANKL binds to the receptor RANK, which is found on the surface of osteoclast precursors.
This stimulates the formation of osteoclasts.
OPG acts as a decoy receptor that binds to RANKL and therefore prevents it from binding to RANK.
This pathway is useful to know as it is targeted by a common drug class for osteoporosis known as RANK ligand inhibitors.
Bone remodeling is a tightly regulated process that involves a balance between osteoclast and osteoblast activity to maintain bone mass, where older and damaged bone is resorbed and new bone is formed.
[upbeat music] Time for a minute physiology.
To understand the physiology behind osteoporosis, there are two main cell types we will focus on.
Osteoblasts are cells that form bone, while osteoclasts resorb or break down bone.
Important building blocks for bones include calcium and phosphate.
Vitamin D also plays a role in this as it increases calcium absorption in the gut and reabsorption in the kidneys.
In osteoporosis, the breakdown of bone by osteoclasts surpass the formation of bone by osteoblasts.
The activity of osteoclasts and osteoblasts are regulated by several other proteins and pathways.
We won't worry too much about going into specific details of these pathways today, but a useful one to know is the RANK/RANKL/OPG system.
In this pathway, RANKL binds to the receptor RANK, which is found on the surface of osteoclast precursors.
This stimulates the formation of osteoclasts.
OPG acts as a decoy receptor that binds to RANKL and therefore prevents it from binding to RANK.
This pathway is useful to know as it is targeted by a common drug class for osteoporosis known as RANK ligand inhibitors.
Bone remodeling is a tightly regulated process that involves a balance between osteoclast and osteoblast activity to maintain bone mass, where older and damaged bone is resorbed and new bone is formed.
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