Posts Tagged ‘Osteoblasts’
A delicate balance between bone formation and bone resorption is needed for Healthy Bone. This balance is naturally present until menopause in a woman or “Low T” in a man. The main players are OsteoBlasts, OsteoClasts, and OsteoCytes.
OsteoBlasts are cells that build bone by producing bone matrix (Anabolic). OsteoClasts are cells that resorb or take away bone (Resorptive). Both live on the surface of bone. OsteoCytes live inside bone and control the balance of formation and resorption through the hormone Osteoprotegrin (OPG). OPG supresses the number and activity of OsteoClasts.
Estradiol is the hormone that tells the OsteoCytes to make enough OPG to keep the Osteoclasts under control. Women make Estradiol from Estrogen. Men make Estradiol from Testosterone. Women after menopause (about age 50) and men after about age 70 no longer make enough Estradiol to produce enough OPG. Then it is Osteoclasts Gone Wild.
Modern Hormone Replacement Therapy (HRT) is an obvious possibility in a woman. Estrogen is back on board. Prolia (Denosumab in osteoporosis dose), and Evista (Raloxifene), are two novel osteoporosis medications designed to bring unruly OsteoClasts under control. They both mimic the natural process, but in different ways. We will address each in coming posts.
Take Back Control with whatever medication works best for you.
Jay Ginther, MD
Bisphosphonates accumulate in your bone. When OsteoClasts gobble up your bone, bisphosphonates are released into the Osteoclasts and disable or kill the Osteoclasts. This is great news when the problem is Osteoclasts Gone Wild. Bisphosphonates preserve bone by slowing down bone resorption. However, after a few months, bone formation by OsteoBlasts also slows down, resulting in slow bone turnover.
Moderate and balanced bone turnover is good. You repair microcracks in your bone when OsteoClasts resorb the bone around them and OsteoBlasts fill in the void with new bone matrix. A mix of new and old bone is far stronger than all old bone. Some OsteoClast activity is necessary to heal fractures, especially incomplete (stress) fractures. That is where long term bisphosphonates can be too much of a good thing.
Are your bones still good enough and just need to be maintained? Or have you fractured several times and need to rebuild your bones? Are Steroid Inhalers supressing your Osteoblasts – the cells that build new bone? (not good) Or have your Osteoclasts – the cells that eat away bone – gone wild (even worse) now that you are post-menopausal or an older guy?
Different problems require different classes of medication. Bisphosphonates, Hormone Replacement Therapy, Synthetic Estrogen Receptor Modifier – Evista, and RANK-Ligand Antibody – Prolia, are all Antiresorptives, which act in different ways. They slow down the Osteoclasts that have gone wild and are eating up the bone. The Anabolic, Forteo, stimulates the Osteoblasts that make new bone matrix. Antiresorptive and Anabolic are radically diferent actions.
Glucocorticoid Induced OsteoPorosis is more common than we thought. Individuals with Rheumatoid arthritis, fibromyalgia, and other inflamatory diseases often need Prednisone and other steroids (glucocorticoids). 3 months of Prednisone 5 mg or more daily induces GIOP. 3-6 months of Prednisone at over 2.5 mg daily can also lead to GIOP. And both of these are total lifetime dose.
Many inhalers for asthma and COPD also contain steroids. Steroids suppress OsteoBlasts, the cells that make new bone to replace resorbed bone. A year or more of inhalers is thought to be the threshhold for ill effects.
Now we are finding out about “Cortisone” (glucocorticoid) Injections into knees and other joints.