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PubMed This is a summary of 16 peer-reviewed journal articles Updated
Endocrinology

The Biology of Bone Loss: Remodeling and Root Causes

At a Glance

Osteoporosis occurs when the natural bone remodeling cycle loses its balance, meaning more bone is broken down by osteoclasts than rebuilt. This can be caused by aging and menopause (primary) or by other medical conditions and medications like steroids or diabetes (secondary).

To understand why bones become fragile, it helps to look at the “conversation” happening inside your skeleton every day. Bone is not a static material; it is a dynamic tissue that is constantly being dismantled and rebuilt. When this cycle works correctly, your skeleton remains strong and resilient.

The Balancing Act: Builders, Breakers, and Shields

The bone remodeling cycle relies on a specialized communication system known as the RANKL pathway. This system involves three main players that determine whether you are gaining or losing bone:

  • The Breakers (Osteoclasts): These cells are responsible for resorption, the process of breaking down old or damaged bone [1].
  • The Signal (RANKL): This is a protein produced by your body that acts like an “on-switch.” When RANKL attaches to the breakers, it tells them to start dissolving bone [2].
  • The Shield (OPG): Your body also produces a “decoy” or shield called osteoprotegerin (OPG). OPG’s job is to intercept the RANKL signal before it reaches the breakers, effectively preventing excessive bone loss [1][3].

In a healthy body, the signal and the shield are in balance. In osteoporosis, the balance shifts: the signal (RANKL) becomes too strong, or the shield (OPG) becomes too weak, leading to more bone being broken down than rebuilt [4].

Primary vs. Secondary Osteoporosis

Doctors categorize osteoporosis based on what is driving the imbalance in the remodeling cycle:

  • Primary Osteoporosis: This is the most common form. It is typically caused by the natural process of aging or the significant drop in estrogen that occurs after menopause [5][6]. Estrogen acts as a natural protector for bones; when it declines, the “breakers” often become overactive.
  • Secondary Osteoporosis: This occurs when the bone loss is a side effect of another medical condition or a specific medication [5][7]. It is important to identify secondary causes because treating the underlying issue can often help stabilize your bone health.

Health Conditions That Drive Bone Loss

Several common conditions and treatments can disrupt the bone remodeling cycle or “poison” the construction site where new bone is made:

  • Glucocorticoids (Steroids): Medications like prednisone are a leading cause of secondary osteoporosis. They are double-edged: they directly increase the RANKL “breakdown” signal and simultaneously cause the “building” cells to die off prematurely [8][9].
  • Cancer Treatments and Early Menopause: Treatments that lower estrogen (like aromatase inhibitors for breast cancer) or androgen deprivation therapy for prostate cancer remove the protective effect on bones, causing rapid bone loss [10][6]. Similarly, premature menopause (before age 45) can jumpstart this process earlier in life.
  • Diabetes: Both Type 1 and Type 2 diabetes can impair bone quality. Chronic inflammation and high blood sugar levels can interfere with the bone-building cells, making the bones more brittle even if they still look “dense” on a scan [11][12].
  • Chronic Kidney Disease (CKD): Because the kidneys help regulate the minerals (like calcium and phosphorus) needed for bone health, kidney disease can lead to a complex mineral imbalance that weakens the skeleton [13][14].
  • Hyperparathyroidism: If your parathyroid glands are overactive, they release too much hormone that tells the body to pull calcium out of the bones and into the blood, causing rapid bone loss [15][16].

Understanding these biological drivers helps your medical team create a treatment plan that addresses the root cause of your bone loss, rather than just the symptoms.

Common questions in this guide

What is the difference between primary and secondary osteoporosis?
Primary osteoporosis is generally caused by the natural aging process and the drop in estrogen during menopause. Secondary osteoporosis occurs when bone loss is a direct side effect of another medical condition or a specific medication, such as diabetes or steroids.
How do steroid medications like prednisone affect my bones?
Steroids can increase the signals in your body that break down bone, while simultaneously causing bone-building cells to die off early. This double-edged effect makes them a leading cause of secondary osteoporosis.
Does diabetes increase my risk of osteoporosis?
Yes, both Type 1 and Type 2 diabetes can impair your bone quality. High blood sugar and chronic inflammation interfere with bone-building cells, making your bones more brittle even if they still look dense on a bone scan.
Can treating a secondary condition stop my bone loss?
If your osteoporosis is driven by an underlying health issue, such as hyperparathyroidism or a medication side effect, identifying and treating that root cause can often help stabilize your bone health.
What is the RANKL pathway and how does it cause bone loss?
The RANKL pathway is a biological communication system that controls bone breakdown. In osteoporosis, the RANKL signal becomes too strong, causing specialized cells called osteoclasts to dissolve more bone than your body can replace.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on my medical history, do you suspect my osteoporosis is primary or secondary?
  2. 2.How do my other medications, particularly any steroids or diabetes treatments, affect my bone density?
  3. 3.Should I have blood tests to check my parathyroid hormone (PTH) and kidney function to rule out secondary causes?
  4. 4.Does my diabetes change the way you interpret my bone density (DXA) results?
  5. 5.If a secondary condition is causing my bone loss, will treating that condition be enough to stop the osteoporosis?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (16)
  1. 1

    Osteoclast differentiation by RANKL and OPG signaling pathways.

    Udagawa N, Koide M, Nakamura M, et al.

    Journal of bone and mineral metabolism 2021; (39(1)):19-26 doi:10.1007/s00774-020-01162-6.

    PMID: 33079279
  2. 2

    RANKL biology.

    Takegahara N, Kim H, Choi Y

    Bone 2022; (159()):116353 doi:10.1016/j.bone.2022.116353.

    PMID: 35181574
  3. 3

    The RANK-RANKL-OPG System: A Multifaceted Regulator of Homeostasis, Immunity, and Cancer.

    De Leon-Oliva D, Barrena-Blázquez S, Jiménez-Álvarez L, et al.

    Medicina (Kaunas, Lithuania) 2023; (59(10)) doi:10.3390/medicina59101752.

    PMID: 37893470
  4. 4

    Iron overload induced osteocytes apoptosis and led to bone loss in Hepcidin-/- mice through increasing sclerostin and RANKL/OPG.

    Ma J, Wang A, Zhang H, et al.

    Bone 2022; (164()):116511 doi:10.1016/j.bone.2022.116511.

    PMID: 35933095
  5. 5

    Parathyroid carcinoma as an overlooked etiology of osteoporosis in postmenopausal women: a case report.

    Su J, Lei S, Jin M, et al.

    Frontiers in endocrinology 2025; (16()):1652919 doi:10.3389/fendo.2025.1652919.

    PMID: 41659338
  6. 6

    Clinical challenges and considerations in pharmacotherapy of osteoporosis due to menopause.

    Palacios S, González SP, Sánchez-Prieto M, Fasero M

    Expert opinion on pharmacotherapy 2024; (25(10)):1359-1372 doi:10.1080/14656566.2024.2383639.

    PMID: 39039930
  7. 7

    Proceedings of the 2016 Santa Fe Bone Symposium: New Concepts in the Management of Osteoporosis and Metabolic Bone Diseases.

    Lewiecki EM, Bilezikian JP, Bukata SV, et al.

    Journal of clinical densitometry : the official journal of the International Society for Clinical Densitometry 2017; (20(2)):134-152 doi:10.1016/j.jocd.2017.01.001.

    PMID: 28185765
  8. 8

    Osteocyte apoptosis: the roles and key molecular mechanisms in resorption-related bone diseases.

    Ru JY, Wang YF

    Cell death & disease 2020; (11(10)):846 doi:10.1038/s41419-020-03059-8.

    PMID: 33046704
  9. 9

    Glucocorticoid Receptor Regulates TNFSF11 Transcription by Binding to Glucocorticoid Responsive Element in TNFSF11 Proximal Promoter Region.

    Lovšin N, Marc J

    International journal of molecular sciences 2021; (22(3)) doi:10.3390/ijms22031054.

    PMID: 33494362
  10. 10

    Prediction of fragility fractures in men with prostate cancer under androgen deprivation therapy: the importance of a multidisciplinary approach using a mini-invasive diagnostic tool.

    Mazziotti G, Lania AG, Laganà M, Berruti A

    Endocrine 2024; (83(3)):594-596 doi:10.1007/s12020-023-03613-2.

    PMID: 38112923
  11. 11

    Musculoskeletal manifestations of diabetes mellitus - an update.

    Ward H, Jawad AS

    Clinical medicine (London, England) 2025; (26(1)):100498 doi:10.1016/j.clinme.2025.100498.

    PMID: 40796059
  12. 12

    The role of diabetes mellitus and BMI in the surgical treatment of ankle fractures.

    Lanzetti RM, Lupariello D, Venditto T, et al.

    Diabetes/metabolism research and reviews 2018; (34(2)) doi:10.1002/dmrr.2954.

    PMID: 29031012
  13. 13

    Management of osteoporosis in patients with chronic kidney disease.

    Abdalbary M, Sobh M, Elnagar S, et al.

    Osteoporosis international : a journal established as result of cooperation between the European Foundation for Osteoporosis and the National Osteoporosis Foundation of the USA 2022; (33(11)):2259-2274 doi:10.1007/s00198-022-06462-3.

    PMID: 35748896
  14. 14

    Association of Serum Osteoprotegerin Levels with Bone Loss in Chronic Kidney Disease: Insights from the KNOW-CKD Study.

    Kim CS, Bae EH, Ma SK, et al.

    PloS one 2016; (11(11)):e0166792 doi:10.1371/journal.pone.0166792.

    PMID: 27855207
  15. 15

    An underdiagnosed manifestation: Mandibular bone loss in primary hyperparathyroidism.

    Helvaci BC, Horoz M, Unver CK, et al.

    Bone 2025; (200()):117598 doi:10.1016/j.bone.2025.117598.

    PMID: 40769418
  16. 16

    Role of nitric oxide in type 1 diabetes-induced osteoporosis.

    Jeddi S, Yousefzadeh N, Kashfi K, Ghasemi A

    Biochemical pharmacology 2022; (197()):114888 doi:10.1016/j.bcp.2021.114888.

    PMID: 34968494

This page explains the biology and causes of osteoporosis for educational purposes only. Always consult your healthcare provider to discuss your specific bone density, risk factors, and diagnostic results.

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