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Parathyroid hormone may reduce chronic low back pain in spinal degeneration by strengthening vertebral endplates and suppressing pain-associated nerve ingrowth through a bone-derived guidance pathway centred on Slit3
Low back pain remains one of the most prevalent causes of disability worldwide. For many people, symptoms persist for months or years and can disrupt sleep, mobility, employment and overall quality of life. Clinicians have continued to face a persistent diagnostic and therapeutic challenge because, in a large proportion of cases, pain cannot be sourced to a single identifiable injury. Against that background, a recent study has reported evidence that parathyroid hormone may relieve chronic low back pain which has been linked to spinal degeneration by limiting aberrant sensory nerve growth within damaged spinal tissue.
Dr Janet L. Crane at the Center for Musculoskeletal Research in the Department of Orthopedic Surgery at Johns Hopkins University School of Medicine in Baltimore, Maryland, USA, led the work. It focused on a question that has drawn intense interest in spine biology and pain medicine asking how degenerative change in bone-adjacent structures reshapes the local neural environment and amplifies pain signalling.
Rather than treat bone deterioration and pain as separate phenomena, the investigators examined whether osteoblast-driven molecular signalling could actively regulate nerve invasion into spinal regions that normally remain relatively free of pain-sensing fibres.
“During spinal degeneration, pain-sensing nerves grow into regions where they normally do not exist. Our findings show that parathyroid hormone can reverse this process by activating natural signals that push these nerves away,” said Dr Crane.
Parathyroid hormone – produced by the parathyroid glands – has an established role in calcium homeostasis and bone remodelling, and synthetic analogues have already entered routine clinical use for osteoporosis. Earlier experimental and clinical observations have suggested analgesic effects in some bone-related conditions, but mechanism-level evidence has remained limited.
To address that gap, the team used three complementary mouse models that recapitulated common routes to spinal degeneration:
This design allowed the researchers to test whether any observed effect persisted across biologically distinct disease contexts rather than in a single model system.
Animals received daily parathyroid hormone administration for treatment windows from two weeks to two months, while control groups received inactive comparator solutions. The investigators then combined structural and functional readouts. High-resolution imaging assessed vertebral endplate integrity, while behavioural assays evaluated pressure sensitivity, heat withdrawal latency and movement-related activity. This multimodal strategy enabled the team to correlate tissue-level changes with pain-relevant phenotypes, an important step in translational preclinical pain research.
After one to two months of treatment, mice exposed to parathyroid hormone showed more stable vertebral endplate architecture, including reduced porosity in the thin interface layers that separate intervertebral discs from adjacent vertebral bone.
In parallel, treated animals tolerated mechanical pressure more effectively, showed delayed withdrawal in heat-sensitivity tests and maintained higher levels of activity than untreated comparators. Taken together, these findings suggested that tissue remodelling and pain behaviour shifted in the same direction under hormone treatment.
The investigators also quantified aberrant spinal innervation, a hallmark increasingly linked to chronic pain in degenerative disease. Degenerated tissue typically showed expansion of sensory fibres into inappropriate microanatomical niches. Parathyroid hormone treatment reduced this ectopic innervation signal, including reductions in fibres marked by protein gene product 9.5 and calcitonin gene-related peptide, both widely used indicators in sensory nerve mapping studies.
Mechanistic experiments then identified a candidate signalling axis with parathyroid hormone stimulating osteoblasts to increase production of Slit guidance ligand 3 – Slit3 – a molecular cue with known axon-guidance activity. In this context, Slit3 appeared to function as a local repellent signal that restricted nerve fibre extension into vulnerable degenerative tissue. In vitro assays supported that interpretation given that when cultured neurons encountered Slit3, neurite extension shortened and invasive growth patterns declined.
When the team removed Slit3 genetically from osteoblast-lineage cells in mice, parathyroid hormone no longer produced the same reduction in aberrant innervation and no longer delivered the same degree of pain-related behavioural benefit. The researchers further identified forkhead box A2 – FoxA2 – as a transcriptional regulator that helped drive Slit3 expression in response to parathyroid hormone signalling. This linked endocrine input to a specific osteoblast transcriptional programme and then to altered neural patterning in degenerative spine tissue.
The findings have added a biologically coherent framework to observations from osteoporosis care in which some patients have reported less back pain during parathyroid hormone-based treatment. That said, the authors were clear about translational limits. The data arose from animal models, and direct clinical extrapolation would require rigorous human studies.
“Our study suggests that PTH treatment of LBP during spinal degeneration may reduce aberrant innervation, laying the foundation for future clinical trials exploring the efficacy of PTH as a disease-modifying and pain-relief treatment for spinal degeneration,” said Dr Crane.
If replicated in human cohorts, the work may help reposition chronic low back pain in spinal degeneration as a condition that is not solely mechanical or inflammatory, but also ‘neuroarchitectural’, in which bone cells participate in active control of nociceptive territory. That concept could open a route to mechanism-led therapeutics that modify disease biology while also reducing symptoms, rather than relying only on broad analgesia after pain pathways have already sensitised.
For further reading please visit: 10.1038/s41413-025-00488-z
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