Gut Microbiome Implicated in Bone Density Variation Among Primary Hyperparathyroidism Patients

Gut Bacteria Linked to Bone Density in Hyperparathyroidism Patients

A study published on 25 May 2026 in Bone Research identifies the gut microbiome, specifically Bifidobacterium longum, as a key factor influencing bone density loss in patients with primary hyperparathyroidism.

Study Methodology

Researchers analyzed stool samples, bone density measurements, and immune-cell profiles from 50 PHPT patients. They conducted fecal microbiota transfer (FMT) experiments, transferring gut microbiota from PHPT patients with osteoporosis, osteopenia, or normal bone density into germ-free mice.

In separate experiments, germ-free mice were colonized with Bifidobacterium longum and exposed to elevated parathyroid hormone (PTH).

Key Findings

• Mice receiving microbiota from osteoporotic patients developed greater bone loss and increased levels of inflammatory immune cells, specifically TNF-producing T cells (TNF+ T cells) and Th17 cells, compared to mice receiving microbiota from patients with normal bone density.
• In germ-free mouse models colonized with Bifidobacterium longum and exposed to elevated PTH, mice experienced greater bone loss than control mice. The colonization stimulated expansion of TNF+ T cells and Th17 cells in the intestine and bone marrow, and enhanced their migration to the bone marrow.

• Higher abundance of Bifidobacterium longum in patient stool samples was associated with higher expression of TNF and IL-17, inflammatory molecules known to promote bone resorption, and with lower bone mineral density.
• No significant differences in overall microbiome composition were found between patient groups with osteoporosis, osteopenia, or normal bone density.

Immune Cell Involvement

Two immune cell populations—TNF-producing T cells and Th17 cells—were identified as mediators between the gut microbiome and bone deterioration. Higher levels of these cells were associated with lower bone density in PHPT patients and in recipient mice in the FMT experiments.

Study Details

• Title: Bacterial specificity of the gut microbiome predicts bone density in primary hyperparathyroidism
• Journal: Bone Research
• DOI: 10.1038/s41413-026-00529-1
• Lead Author: Roberto Pacifici (Emory University)
• Funding: NIH grants DK124821 and RR028009 (to R.P.) and DK09839 (to R.M.J.); Emory Integrated Computational Core Facility; Emory gnotobiotic core; VA Medical Health Research Career Scientist Award IK6RD001819 (to M.N.W.)

Implications

"The extent to which primary hyperparathyroidism impacts the human skeleton correlated with the abundance of Bifidobacterium longum... These findings confirmed that the presence of Bifidobacterium longum in the gut microbiome allows PTH to cause the expansion and migration of TNF+ T cells and Th17 cells and to induce bone loss."
— Lead author Roberto Pacifici

The study suggests that the gut microbiome may directly influence the severity of bone loss in PHPT. Bifidobacterium longum and associated immune signatures could serve as biomarkers for osteoporosis risk. The authors propose that targeted microbiome interventions, such as selective microbial modulation, antibiotics, or precision probiotics, may offer new therapeutic approaches to prevent or reduce bone loss in PHPT patients.