Johns Hopkins Discovered Why Your Back Pain Gets Worse With Age, and a Hormone That May Stop It

By Dr. Jason Forward, DC. Practicing chiropractor in Tulsa, Oklahoma. Posted April 17, 2026.

What the Researchers Found

The study was led by Dr. Janet Crane's team at the Johns Hopkins Center for Musculoskeletal Research. They were investigating a basic question: why does back pain from degenerating discs get worse over time, even when the structural damage does not change much on imaging?

The answer, they found, involves abnormal nerve growth.

In a healthy spine, the vertebral endplates (the thin layers of bone between your discs and vertebrae) are mostly free of nerve fibers. They serve as a barrier. But when those endplates start degenerating, the barrier breaks down. Pain-sensing nerve fibers, marked by proteins called PGP9.5 and CGRP, grow into the damaged endplate tissue. These are the same fibers that transmit pain signals to your brain.

More nerve fibers in damaged tissue means more pain signals. That is why a disc that looked the same on MRI three years ago can hurt significantly more today. The structural damage may not have changed. The nerve supply did.

How Parathyroid Hormone Reverses the Process

PTH is a hormone your body already produces. Its primary job is regulating calcium and bone metabolism. It tells osteoblasts (bone-building cells) to form new bone. Doctors already use a synthetic version of it (teriparatide, brand name Forteo) to treat severe osteoporosis.

The Johns Hopkins team discovered something PTH does that nobody expected. When PTH activates osteoblasts in the vertebral endplate, those cells produce a guidance protein called Slit3. Slit3 is a nerve repellent. It pushes growing nerve fibers away from areas where they do not belong.

The signaling pathway works like this:

1. PTH binds to receptors on osteoblasts in the vertebral endplate.
2. A protein called FoxA2 activates inside those cells.
3. FoxA2 triggers the production of Slit3.
4. Slit3 is secreted into the surrounding tissue.
5. Growing pain-sensing nerve fibers encounter Slit3 and are repelled, retreating from the endplate.

In the mouse model, one to two months of PTH injections led to measurably denser vertebral endplates, significantly fewer nerve fibers in the endplate tissue, and reduced pain-related behaviors.

Why This Matters (Even Though It Is an Animal Study)

I want to be clear about something. This research was conducted in mice. Not in humans. No one should read this and go ask their doctor for PTH injections for back pain. That is not where the science is yet.

But the mechanism this study describes is real and observable in human tissue. We have known for years that degenerating discs in humans show abnormal nerve ingrowth. Previous human histological studies have documented it. What we did not have was a clear understanding of how to reverse it, or even whether reversing it was possible.

Johns Hopkins just showed it is possible in an animal model. That is a significant step. The pathway from animal study to human clinical trial to approved therapy is long. It typically takes 5 to 15 years. But the foundational science is now in place.

The Mechanical Side: What We Can Do Right Now

While researchers work on the biochemical solution, patients with degenerating discs still need to manage their pain today. That is where the clinical picture gets practical.

Disc degeneration creates two overlapping problems:

Problem 1: Abnormal nerve ingrowth (the biochemical side). This is what the Johns Hopkins study addresses. Nerves grow where they should not, amplifying pain signals. There is no clinical treatment for this yet in humans.

Problem 2: Mechanical dysfunction (the structural side). As discs lose height and hydration, the joints above and below compensate. Facet joints take on more load. Surrounding muscles tighten to splint the area. Range of motion decreases. The segments above and below the degenerated disc start moving too much to make up for the segment that is stuck. This creates secondary pain generators that layer on top of the disc-related pain.

Chiropractic care addresses Problem 2 directly. When I adjust a spine with degenerative changes, I am not trying to fix the disc. Discs do not un-degenerate. What I am doing is restoring motion to the restricted segments, reducing the compensatory load on surrounding joints, calming the muscular guarding pattern, and improving the mechanical environment around the degenerated level.

Patients with disc degeneration who receive regular chiropractic care often report meaningful improvement in daily function, even though the disc itself has not changed. This study helps explain why that matters: if the mechanical environment is managed well, it may reduce the stimulus that drives abnormal nerve growth in the first place.

What I Tell Patients With Disc Degeneration in Tulsa

At Vanguard Chiropractic, I see disc degeneration patients every week. Some are in their 40s with early changes. Some are in their 70s with significant multilevel degeneration. Here is what I tell all of them:

Disc degeneration is normal. It happens to virtually everyone as they age. Having degeneration on an MRI does not mean you are broken or destined for surgery. Studies show that up to 90% of people in their 60s have disc degeneration on imaging, and many of them have zero symptoms.

Pain from degeneration is not constant or inevitable. The level of pain you experience depends heavily on the mechanical health of the surrounding structures, your movement habits, your muscle strength, and your nervous system's sensitivity. All of those things are modifiable.

Conservative care first. Surgery is appropriate when there is severe nerve compression causing weakness, bowel/bladder dysfunction, or progressive neurological loss. For the majority of degenerative disc patients, conservative management with manual therapy, exercise, and activity modification is the first-line approach. Clinical guidelines from the American College of Physicians support this.

Stay moving. Motion is the single best thing for degenerating discs. Movement pumps fluid into and out of disc tissue, reduces joint stiffness, and keeps surrounding muscles from atrophying. Bed rest makes everything worse.

The Bigger Picture: Biochemistry Meets Biomechanics

This Johns Hopkins study is exciting because it points toward a future where we can address both sides of the degenerative pain equation. The biochemical side (nerve ingrowth, inflammatory signaling, structural breakdown) and the mechanical side (joint restriction, muscle guarding, compensatory overload) are not separate problems. They feed each other.

If PTH-based therapies eventually prove effective in humans, they would address the nerve ingrowth issue that makes degeneration increasingly painful. Combined with manual therapy that manages the mechanical dysfunction, that would give patients a much more complete treatment strategy than either approach alone.

We are not there yet. But the fact that researchers at one of the top medical institutions in the world are publishing this level of detail about the mechanism gives me real optimism about where this is heading.

When to See a Doctor Instead

Not all back pain from disc degeneration is appropriate for chiropractic care alone. Red flags that warrant medical evaluation include:

• Progressive weakness in one or both legs
• Loss of bowel or bladder control
• Numbness in the saddle region (inner thighs, groin)
• Back pain with fever, unexplained weight loss, or history of cancer
• Pain after significant trauma (fall, accident)

If any of these apply to you, see a medical doctor or go to an emergency department first. These are not chiropractic conditions. They may require urgent imaging and intervention.